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Magnetic Materials and Magnetism - Science topic

Magnetic Materials and Magnetism is a discussion about magnetic, magnetoelectric and magnetoresistive materials
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I have learnt that a simple ferro magnetic fluid can be made by mixing Black Iron Oxide (Fe3O4) and a viscous fluid like oil. I purchased black oxide from a hardware store. When I bring the powder near a magnet (loudspeaker magnet - the only magnet at my disposal) it is not at all responding, why is that?
I saw many videos on the internet making ferromagnetic fluids by mixing black oxide and some viscous media.
My question is if it is working for them why is it not working for me? What went wrong?
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  1. Supplies. black iron oxide powder.
  2. Add a small scoop of an iron oxide powder to a clean and dry glass container.
  3. Seal With Caulking.
  4. Add Magnet.
  5. Ferromagnetic Fluid With Oil.
  6. Add Oil and Mix.
  7. Introduce Magnet.
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I have a semiconducting material that is diamagnetic in nature. On doping with magnetic ions, it shows paramagnetic behaviour. Further on substituting a non-magnetic ion into the system, it shows a small hysteresis curve. Magnetoresistance study of the sample shows negative behaviour at lower values of temperature and positive behaviour as temperature increases. What does this transition indicate?
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Relative to Ferro negative MR should be low in Para ideally, but it can depend on the spin orientation with magnetic field and temperature. If spin orientation is more, it will be more. Check with the area of the loop and corecivity.
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Dear expert users of the SPRKKR package,
Can someone give me guidelines to resolve convergence issues in the SCF run? For pure compound, the SCF cycle gets converged quickly (within 50 electronic iterations), but with substitutional doping (~ 2%), all the maximum allowed iteration (300) gets exhausted, and the system doesn't converge. The details of the input file and error message are as follows:
Input
MODE SP-SREL
LLOYD
TAU BZINT= POINTS NKTAB= 250
ENERGY GRID={5} NE={30}
ImE=0.0 Ry EMIN=-0.2 Ry
SCF NITER=300 MIX=0.101 VXC=PBE
TOL=0.00001 MIXOP=0.20 ISTBRY=1
QIONSCL=0.80
NOSSITER
Error
*******************************************************************************
no problems with CPA-cycle !
*******************************************************************************
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300 ERR 0.113E+01 0.698E-01 EF 0.78274 -0.00105 D 83.132 M 3.0776 0.0000
ETOT -10814.43503634 SCF - cycle not converged - NSCFITER exhausted
*******************************************************************************
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Thank you, Jaafar Jalilian , for your quick reply!
Yes, the parent compound was optimized using VASP, but not the doped structures. I am unsure whether any relaxation (ionic positions or volume) procedure is available in the SPRKKR package. Please let me know if it is available, and I am very new to the package.
The package uses CPA approximations for the doping calculations, so it doesn't provide any supercell that could be optimized using VASP. I am interested in calculating exchange interaction with the Lichtenstein approach using the SPRKKR package.
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I want make silica coated magnets but I have several problem in procedure. I cant make high quality silica coated magnets.
Results show a poor yield so i think many of magnets don't be coated.
How can i increase silica coated magnets or how can i increase coating with silica?
How can i separate silica coated magnet and non coated magnets ?
What is the best protocols to produce silica coated magnets?
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Dear Ehsan Razeghian, the choice of the solvent has a detrimental role for success. Methanol is usually the best option. Please have a look at the following documents. My Regards
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The exploration of concealed porphyry Cu Au deposits is challenging as their footprints in aeromagnetic surveys can be rather complex depending on the respective magnetic susceptibilities of their wallrocks and possible postmineral tectonic overprints or structural offsets. Unfortunately, magnetic anomalies of porphyry Cu deposits are poorly documented (and illustrated) in the literature. However, locally their magnetic responses consist of two rather distinct subtypes: 1) magnetic bulls eye and 2) magnetic doughnut anomalies.
The most common magnetic response of a hydrothermal porphyry system is a distinct magnetic high anomaly, typically measuring several hundred meters in diameter, and reflecting the magnetite-rich potassic altered core. A well documented example is the Bajo de la Alumbrera porphyry Cu Au deposit, Catamarca Province, Argentina (Fig. 1). During the waning and cooling stages of the hydrothermal system, cooler late-stage fluids can overprint the stockwork mineralization and its associated potassic alteration assemblage. This may lead to the subsequent oxidation (i.e. martitization) of hydrothermal magnetite to hematite. This process may cause the de-magnetization of the magnetic high into a “doughnut-shaped” or “torus-like” magnetic anomaly as recorded at the Northparkes and Cadia porphyry Cu Au clusters in the Lachlan Fold Belt in N.S.W., Australia (Fig. 2). The latter type of magnetic anomalies appears to be more common at alkalic porphyry Cu Au deposits that are hosted by high potassic and shoshonitic intrusions.
I should be grateful for any comments on this topic! Additional illustrations of magnetic anomalies of porphyry Cu deposits are most welcome! Many thanks.
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Dear Dr. Muller,
Here is the list of references about magnetic responses of porphyry deposits (most of them only include a brief paragraph about magnetic data). The best ones are the works by Dr. Clark. I hope it helps.
Regards,
Reza
References:
Gunn, P.J., Dentith, M., (1997): Magnetic responses associated with mineral deposits, AGSO Journal of Autralian Geology & Geophysics, Vol. 17, No. 2, pp. 145-158.
Clark, 2014, Magnetic effects of hydrothermal alteration in porphyry copper and iron-oxide copper-gold systems: A review, Tectonophysics, Vol. 624.
Clarck, D.A., French, D.H., Lackie, M.A., Schmidt, P.W., (1992): Magnetic petrology: Application of integrated rock magnetic and petrological techniques to geological interpretation of magnetic surveys, Exploration Geophysics, Vol. 23, pp. 65-68.
Oldenburg, D.W., Li, Y., Ellis, R.G., (1997): Inversion of geophysical data over a copper gold porphyry deposit: A case history for Mt. Milligan, Geophysics, Vol. 62, No. 5, pp. 1419-1431.
Hildenbrand, T.G., Berger, B., Jachens, R.C., Ludington, S., (2000): Regional Crustal Structures and Their Relationship to the Distribution of Ore Deposits in the Western United States, Based on Magnetic and Gravity Data, Economic Geology, Vol. 95, pp. 1583-1603.
Behn, G., Camus, F., Carrasco, P., Ware, H., (2001): Aeromagnetic Signature of Porphyry Copper Systems in Northern Chile and Its Geologic Implications, Economic Geology, Vol. 96, pp. 239-248.
Clarck, D.A., Schmidt, P.W., (2001): Petrophysical Properties of the Goonumbla Volcanic Complex, NSW: Implications for Magnetic and Gravity Signatures of Porphyry Cu-Au Mineralisation, Exploration Geophysics, Vol. 32, pp. 171-175.
Clarck, D.A., Guena, S., Schmidt, P.W., (2004): PREDICTIVE MAGNETIC EXPLORATION MODELS FOR PORPHYRY, EPITHERMAL AND IRON OXIDE COPPER-GOLD DEPOSITS: IMPLICATIONS FOR EXPLORATION, Exploration and Mining Report 1073R, CSIRO Exploration & Mining / Amira International Limited.
OSSANDÓN, G., FRÉRAUT, R., GUSTAFSON, L.B., LINDSAY, D.D., ZENTILLI, M., (2001): Geology of the Chuquicamata Mine: A Progress Report, Economic Geology, Vol. 96, pp. 249-270.
Ford, K., Keating, P., Thomas, M.D., (2007): OVERVIEW OF GEOPHYSICAL SIGNATURES ASSOCIATED WITH CANADIAN ORE DEPOSITS. (Available at: http://www.openground.co.za/wp-content/plugins/jb_fileUploader/files/Overview%20of% 20Geophysical%20Signatures%20Associated%20with%20Canadian%20.pdf)
Berger, B., Ayuso, R.A., Wynn, J., Seal, R.R., (2008): Preliminary Model of Porphyry Copper Deposits.
Purucker, M.E., Clarck, D.A., (2010): Mapping and Interpretation of the Lithospheric Magnetic Field, Geomagnetic Observations and Models, pp. 311-337.
Chang, Z., Hedenquist, J.W., White, N.C., Cooke, D.R., ROACH, M., Deyell, C.L., Garcia, J., Gemmell, J.B., McKnight, S., Cuison, A.L., (2011): Exploration Tools for Linked Porphyry and Epithermal Deposits: Example from the Mankayan Intrusion-Centered Cu-Au District, Luzon, Philippines, Economic Geology, Vol. 106, pp. 1365-1398.
Holden, E., Fu, S.C., Kovesi, P., Dentith, M., Broune, B., Hope, M., (2011): Automatic identification of responses from porphyry intrusive systems within magnetic data using image analysis, Journal of Applied Geophysics, Vol. 74, pp. 255–262. (doi:10.1016/j.jappgeo.2011.06.016)
Hoschke, T., (2012): Geophysics of the Elang Cu-Au porphyry deposit, Indonesia, and comparison with other Cu-Au porphyry systems, 22nd International Geophysical Conference & Exhibition, Brisbane, Australia.(https://doi.org/10.1071/ASEG2012ab178)
Anderson, E.D., (2013): AEROMAGNETIC SIGNATURE OF THE GEOLOGY AND MINERAL RESOURCES NEAR THE PEBBLE PORPHYRY CU-AU-MO DEPOSIT, SOUTHWEST ALASKA, PhD thesis (Geology), Colorado School of Mines. (Available at: https://mountainscholar.org/handle/11124/11)
Mitchinson, D.E., Enkin, R.J., Hart, C.J.R., (2013): Linking Porphyry Deposit Geology to Geophysics via Physical Properties: Adding Value to Geoscience BC Geophysical Data, Geoscience BC Report 2013‐14. (Available at: http://www.geosciencebc.com/i/ project_ data/GBC_Report2013-14/GBC_Report2013-14.pdf)
Clarck, D.A., (2014): Magnetic effects of hydrothermal alteration in porphyry copper and iron-oxide copper–gold systems: A review, Tectonophysics, Vol. 624-625, pp. 46-65. (https://doi.org/10.1016/j.tecto.2013.12.011)
Riveros, K., Veloso, E., Campos, E., Menzies, A., Véliz, W., (2014): Magnetic properties related to hydrothermal alteration processes at the Escondida porphyry copper deposit, northern Chile, Mineralium Deposita, Vol. 49, No. 6, pp. 693–707. (DOI 10.1007/s00126-014-0514-7)
Airo, M.L., (2015): GEOPHYSICAL SIGNATURES OF MINERAl DEPOSIT TYPES – SYNOPSIS, Geological Survey of Finland, Special Paper 58, pp. 9–70. (Available at: http://tupa.gtk.fi/julkaisu/specialpaper/sp_058_pages_009_070.pdf)
Hope, M., Anderson, S., (2016): The discovery and geophysical response of the Atlántida Cu–Au porphyry deposit, Chile, Exploration Geophysics, Vol. 47, No. 3, pp. 237-247. (http://dx.doi.org/10.1071/EG15094)
Shah, A.K., Bedrosian, P.A., Anderson, E.D., Kelley, K.D., Lang, J., (2013): Integrated geophysical imaging of a concealed mineral deposit: A case study of the world-class Pebble porphyry deposit in southwestern Alaska, Geophysics, Vol. 78, No. 5, pp. B317–B328. (10.1190/GEO2013-0046.1)
Mohebi, A., Mirnejad, H., Lentz, D., Behzadi, M., Dolati, A., Kani, A., Taghizadeh, H., (2015): Controls on porphyry Cu mineralization around Hanza Mountain, south-east of Iran: An analysis of structural evolution from remote sensing, geophysical, geochemical and geological data, Ore Geology Reviews, Vol. 69, pp. 187-198.
Kheyrollahi, H., Alinia, F., Ghods, A., (2016): Regional magnetic lithologies and structures as controls on porphyry copper deposits: evidence from Iran, Exploration Geophysics, Vol. 49, No. 1, pp. 98-110. (https://doi.org/10.1071/EG16042)
Anderson, E.D., Hitzman, M.W., Monecke, T., Bedrosian, P.A., Shah, A.K., Kelley, K.D., (2013): Geological Analysis of Aeromagnetic Data from Southwestern Alaska: Implications for Exploration in the Area of the Pebble Porphyry Cu-Au-Mo Deposit, Economic Geology, Vol. 108, pp. 421–436.
Anderson, E.D., Monecke, T., Hitzman, M.W., Zhou, W., Bedrosian, P.A., (2017): Mineral Potential Mapping in an Accreted Island-Arc Setting Using Aeromagnetic Data: An Example from Southwest Alaska, Economic Geology, Vol. 112, pp. 375–396.
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What happens in microstructure of ferromagnetic steel during demagnetization?
Is BCC changing to FCC?
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Stainless steels, for example, can be either magnetic (ferritic steel) or non-magnetic (austenitic). A magnetic steel can decrease its magnetization by increasing the temperature and above the Curie temperature its magnetization is null, but in this process nothing happens with its microstructure except for expansion. Common steels exhibit magnetic behavior that depends on their chemical components and the amount of carbon.
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I have discovered a photochemical way to prepare polycrystal (domain ~5*5 nm^2) gamma-Fe2O3 into any sizes of nanoparticles, or on any substrates to form something like Au@Fe2O3 core-shell nanoparticles in liquid phase.
But to extend the applications, I want to make the Fe2O3 becoming Fe3O4, which is magnetic.
Are there any ways to convert Fe2O3 to Fe3O4 in liquid phase (such as adding NaBH4) or in solid phase (calcination)?
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there are two ways
first adding Fe with only 8.75% Fe2O3 (mass fraction). means a small amount of Fe powder can make Fe2O3 transform into Fe3O4 completely in alkaline aqueous solution
second . Treat hematite at above 350 C in a typical WGS reaction medium like H2+CO2+H2O in the proportion of ca. 45:15:40 .
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Dear all
what is the new and HOT promising diluted magnetic semiconductor materials, that can have ferromagnetic and semiconductor properties close to room temperature? Wich not very difficult to realize (based on typical crystal growth techniques, availability of source)
My question is directed for research purposes, not necessarily for commercial applications.
Please share your knowledge. Additionally, If you know a good paper for this question, please tell me.
Thank you in advance.
Best regards.
Ismail
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Ferromagnetic chalcopyrites II-IV-V2 have Tc ~ 310-350 K and a diamond-like crystal structure compatible with Si and III-V semiconductors. Transition metal doping is possible in these materials over the entire range of concentrations from 0 to 100%. Here are two relevant references:
(1) Room temperature ferromagnetism in novel diluted magnetic semiconductor Cd1-xMnxGeP2, Jpn. J. Appl. Phys. 39(10A), L949-51 (2000);
(2) Magnetic and optical phenomena in nonlinear optical crystals ZnGeP2 and CdGeP2, J. Optical Society Am. B 22 (9), 1884-1898 (2005).
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I have updated my manuscript but its the third time the reviewer send me this comment again.
What are the probable redox reaction during cyclic voltammetry?
Could anyone guide me on this, please
Thanks, A lot in advance for your precious time.
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Dear all, please have a look at the following link and the attached file. My Regards
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For different AFM configurations is it necessary to take symmetric supercell (2x2x2) or asymmetric super cell (2x2x1 or 1x1x2) can also work?
Here I am concerned about Heusler alloys in particular with Hexagonal and tetragonal structure?
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Most Heeusler stoichiometric alloys have a 2x2x2 structure with 16 atoms - such as the full hesler with L21 cubic structure: Fe2CrSi, Fe2MnGa, Fe2MnAl... Therefore, when simulating this type of alloy theoretically, multiples of the 2x2x2 structure are used. From a theoretical point of view, if a bulk alloy is to be studied, nothing prevents the use of non-symmetrical supercells. Now, if you are going to simulate a thin film or multilayer you must be careful so that the supercell used represents what you want to study. Also note that a 2x2x2 supercell does not necessarily must to be symmetrical, it can also have tetragonal deformation, for example.
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I know the properties of a permanent magnet change with temperature and that different magnetic materials have different temperature coefficients. If a permanent magnet has a temperature gradient across its length (i.e one end of the magnet is at a different temperature to the other), which temperature will the properties of the magnet correspond to? Will it act as if the entire temperature is the same as the lowest temperature end, the highest temperature end, or something in between (the mean temperature perhaps?)? Or is it more complex than being able to estimate its properties to a single temperature?
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Please see the attached file.
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Magnetic quadrupoles.
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If the unit of MxH is (emu-Oe/g), what does this unit represent?
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Dear Rakibul,
Please pay attention to the fact that my previous post corrects statements by Amir Aslani and Miguel Angel Cobos Fernández that "You also asked what (emu-oe/g) indicates. This is the magnetization of the material, per 1 gram of that material's mass, per 1 unit of applied magnetic field (in Oersted)" and that "...m(emu) x H(T) = J/T x T ... is energy", contradicting each other by themselves.
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Just curious to make a list of recommended books/study materials explaining Magnetism in condensed matter physics preferably with emphasis on Quantum Magnetism.
I would be glad if you give some references from Bachelors to Ph.D. level.
Thanks & Regards,
KP
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Dear Kaushick Parui , In addition to all those mentioned, the chapter VII of the book:
Statistical Physics, part II: Theory of the Condensed State, Vol. 9 by E. Lifshitz, L. Pitaevskii Elsevier, 2013.
for the Ph.D. Level - Theory. Mainly talks about magnons.
Best Regards.
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I am trying to excite spin-wave in a BLIG film via applying microwave current to one micro-strip line and detecting the transmission at another micro-strip line. The problem I am facing is the transmission due to electromagnetic coupling is masking the spin-wave transmission. Unfortunately, designing a new micro-strip line is not an option at this moment. How to separate the spin-wave transmission part and EM transmission part?
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As commented to similar question a moment ago:
Perhaps you have (microwave) magnetostatic wave devices in mind..there was a lot of research and many PhD thesis in this field about 40 years ago.
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When ferromagnet (FM) and antiferromagnet (AFM) are coupled, exchange bias can be generated at the interface of FM and AFM which acts as a bias field in the hysteresis loop.
I am particularly interested in the case that FM has perpendicular magnetic anisotropy (PMA) and the localized magnetization in AFM lies in the plane. In this case, it is possible to generate an in-plane bias field to the FM layer.
In a system like PtMn + Co/Ni multilayer, where the Curie (Neel) temperature TC (TN) are both very high ( > 300 C), a typical way to induce this in-plane bias field is by applying a large in-plane field (~ 1T) and annealing the sample at ~300 C, which is below TC. I assume that the annealing is required because it is not a good idea to heat the sample above TC and therefore change the property of the material.
Now, my question is: If I have a similar system (FM with PMA, in-plane AFM), but with room temperature > TC >TN, can I induce an in-plane field by applying a large in-plane filed above TN and then cool the sample to a temperature below TN?
Relevant paper:
Annealing to get bias field:
Neel temperature of AFMs:
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the is often a confusion between ferrimagnetic effect and ferromagnetic ;when you use YIG like material In the microwave range) its ferrimagnetic !
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As you can see on the graph, my ZFC curves stand above the FC curves for this group of samples. My department uses a magnetic field of 0.1 T at the VSM and have never seen anything like this. Has anyone ever seen something like this, or can provide any explanation for this phenomenon?
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Dear João Pedro Carvalho,
As I can see from the data, here 1000 degree C sample is I guess only the heat treatment given to the sample, while the measurement is carried out from 300 K to down to few kelvins. First, the point I noticed is that the ZFC and FC are having a non-overlapping range in wide temperature regions. The second point I noticed is that bifurcation occurs in a very low-temperature region. If anything happens due to the magnetic interactions or reorientation of the moment along the magnetic field as an effect of temperature, one should get the systematic change and clear cut bifurcation between ZFC and FC.
Such experimental data (although i don't know the sample detail), I guess with my experience is about the change in sample position with temperature. Any small change in position can affect a change in the signal pick by the secondary coil and hence the magnitude differ. Please check the ZFC FC measurement with auto centring, I suggest at each 20 K or some time interval. If possible then try to measure the ZFC FC at as low as low field possible for eg. 100 Oe ..200 Oe or 500 Oe. I understand its difficult to pick the signal in the very low field, but as per the data shown in the figure, it seems to be a large signal and easy to detect. Further, I will suggest to use inverse susceptibility measurement for analysis of the data. Measurement at 0.1 T (1000 Oe) is little high to probe the real signature coming from the local magnetic interaction. you can also check the MH data at the temperature where the cross over in ZFC FC has occurred. If facility allowed, I would like to suggest for resistivity measurement for knowing the electronic structure change happening if any. If you need any measurement support or analysis using computational tools let us discuss further.
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Can anyone give me the step by step procedure to find the value of magnetic saturation using the law of approach to saturation for BaFe12O19 sample? Thanks!!
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i am getting an error whenever i am running the given attached simulation on ansys maxwell 16.0.
This arrangement consists of two electromagnets housed in two coil of copper winding supplied with ac voltage as shown.
I have given excitation voltage in both the winding separately as shown and boundary condition on coil as shown.
I am using transient solution as type of solution.
Any advice you provide me will be highly valuable.
Thank You
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Did you enclosed the model in a vacuum space or air box?
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I want to know how we can relate magnetostriction with Applied magnetic field mathematically? Or if there is any way to derive it using mechanical equations?
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There are some classic thermodynamic models to discuss the influence of an external magnetic field on magnetostriction. And we can discuss the influence of external magnetic field on magnetostriction in ferromagnetic materials with different initial stress states.
【1】Shi Pengpeng. One-dimensional magneto-mechanical model for anhysteretic magnetization and magnetostriction in ferromagnetic materials. Journal of Magnetism and Magnetic Materials 2021, 168212. https://doi.org/10.1016/j.jmmm.2021.168212
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Hi folks,
Currently running some convergence tests for magneto-crystalline anisotropy energy (MAE) of Fe (e.g. E_111 vs E_110 vs E_001).
As you know calculating MAE requires very strict convergence criteria as the relative energies can be on the order of 1 µeV, and can require k-points on the order of 10,000 or more.
However, the calculation is also dependent on the smearing width, which has a non-negligible influence on the # of k-points required for convergence, and smaller smearing requires higher k-points.
I am currently using VASP with the tetrahedron method with Blöchl corrections (ISMEAR = -5), with 0.01 eV smearing, and I find that 10k k-points is not enough to reach convergance (it has reached only ~ <2 ueV).
Before continuing with a higher k-point density I would like to get some input if 0.01 eV is appropriate, or if raising the value to 0.1 eV, while it may help convergance at smaller k-point mesh size, would impact the accuracy of the MAE energy? At 0.01 eV smearing and 10-kpoints, the relative anisotropy E_111 > E_110 > E_001 of Fe is correctly predicted, but I don't know how accurate the magnitude would change with smearing, or if perhaps I should try even smaller smearing widths.
Thanks in advance,
-B
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Tetrahedron method with Blöchl corrections (ISMEAR=-5) doesn't require empirical parameters such a SIGMA...
"For the calculations of the DOS and very accurate total energy calculations (no relaxation in metals) use the tetrahedron method (ISMEAR=-5)." https://www.vasp.at/wiki/index.php/ISMEAR
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Unless there is some systematic error on the instrumentation used, I have observed an inverted peak when measuring the FMR absorption derivative for a YIG/NM/m-FM thin-film sample. The YIG layer was deposited via magnetron sputtering on GGG(111) substrate and is not monocrystalline but exhibits only a few crystalline phases. The observed anomalous peak is normal at lower frequencies, goes through a change at 2.5 GHz and becomes inverted at the higher range. Another peak observed for the same sample (probably corresponding to a different crystalline phase) is not inverted but at least four times more intense, both at lower and at higher frequencies. Both peaks occur on the same FMR dispersion curve.
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I used broadband multi-frequency stripline technique when I obtained inverted peaks. I interpreted them according to homogeneity of the sample and the standing wave due to reflection within the sample and sample thickness.
I hope these information is useful and let us know if there is an other explanation.
Regards
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I have taken temp Vs time measurements of my iron oxide nanoparticles in an alternating magnetic field. usually the measurements are performed in suspension and the SAR is calculated as per the equation - SAR= Cp dT/dt, where Cp is the specific heat capacity of the suspending medium.
However, in my case there is no medium. So should I take Cp to be the specific heat capacity of air or of my nanoparticle powder?
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Dear Shaquib Rahman Ansari many thanks for the explanation. Perhaps the following article might be useful in that respect:
Specific Absorption Rate Dependence on Temperature in Magnetic Field Hyperthermia Measured by Dynamic Hysteresis Losses (AC Magnetometry)
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I ran VASP relax calculations for Fe in the interstitial position of MgO for different charge states of Fe from 0 to +3. The magnetic moment seems to increase from 2BM to 5BM in steps of 1 as each electron is removed but it not quite consistent with the number of unpaired electrons. Is it possible that a system with a lesser number of unpaired electrons can have a higher magnetic moment?
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As per my knowledge for Fe+2, the number of unpaired electrons is 4 and Magnetic moment will be 4.89 BM.
For Fe+3 ions, the number of unpaired electrons is 5 and magnetic moment will be 5.9 BM.
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As much as I know, there is a proportional relationship between initial permeability and density for a particular composition. It means, if density increases with increasing sintering temperature, the initial permeability of that sample will increase. But, in some cases I have experienced that, density falls but the initial permeability of that sample increases instead of decreasing. Why this kind of phenomenon does happen?
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Have you checked the phase composition of the samples?
Different phases with different grain sizes may be formed under different conditions.
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I'm quite new to VAMPIRE. Any suggestions for finding resources and example codes?
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While the magnetite particles are much above single-domain limit, they indeed form spike-like structure under strong magnetic field. Would not that be predominantly caused by aligning of particles physically rather than realignment of their magnetic domain, due to the not very high temperature and magnetite being ferrimagnetic? If that magnetic orientation is locked by congealing the "spikes" by cement or wax, would that arrangement have a net arranged magnetic field upon withdrawal of external magnetic field, provided that the particles can move no longer? If this is not possible, then why? If possible, then what would be the strength of that magnetic field compared to a bar magnet? (for a comparable distance and geometry)
Will the slurry be fluid enough to allow the magenit spikes to form like in gas or vacuum?(relation between % solid ,% magnetic particles allowed and time to set as well as maximum residual magnetic field of the arrangement are asked; or at least hint to the model). Another point to mention, melting point of wax would be below 100 degrees C to not affect magnetite magnetism, but what would be role of Typical cement chemicals (e.g. portland, plaster of paris) that may chemically degrade the magnetite?
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You might have problems getting the cement slurry liquid enough for the particles to move and align within the magnetic field. If you actually try it, I would recommend using a superplasticizer otherwise you will need a huge amount of water and your product will be very porous. If you use a white cement you could test if spikes did form within by slicing the hardened product. You could be able to see from the magnetite particle distribution if it worked.
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Does anyone hold an original Bosma paper from 1962, "On the principle of stripline circulation”?
I am kind of curious how everyone refer to it blindly without explaining formulas and values, when it is not widely available.
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Dear Andrey Porokhnyuk, attached is the file you are looking for. My Regards
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I am working on orthoferrites and studying their dielectric properties. One of the samples I prepared shows a dielectric relaxation peak (observed in real part of dielectric constant, at high frequency). Near the same frequency range, the imaginary part of dielectric constant take negative value. Is it possible to have negative value of imaginary part of dielectric constant? What does it mean?
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positive imaginary part means gain and negative imaginary part means loss, if you have positive imaginary part, how the gain is possible in a passive device?
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Any close value will also work.
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Dear Abhishek Mukherjee,
The optical absorption coefficient can be obtained by using the equation [2] which can be used in a non-conducting dispersive medium. Here w is photon frequency, μo is the permeability of free space, ε1 and ε2 are frequency-dependent real and imaginary parts of dielectric permittivity from the VASP output of the first-principle calculation.
Refer this article for permeability data
2. D. J. Griffiths . Introduction to Electrodynamics. 4th Edition, Pearson Education (2013).
Ashish
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It seems antiferromagnetic metallic oxide compound is very rare, is there any example compound?
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So far RuO2, CaCrO3, SrCrO3, LaNiO3, Pb2CoOsO6 are the only known examples.
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Magnetic microstructure  What is the substrate influence on the magnetic domains formation in the case of thin films?
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Good question
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What is happening at the interface (grain boundary) between two the phases in multiferroics composite ceramics (CFO-BTO) during sintering process?How do bind the spinel structure and perowskit ?
how is the effect of different sintering temperature here? And what is the correlation between the two interfaces properties and magnetoelectric coefficient?
Experimentaly: How can coupling between the different ferroics oders can measured in grain boundaries?
Recommendation of papers on this question is welcome
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Science does not stand still. New opportunities for research keep appearing and, as a result, new findings and discoveries happen hand to hand with artifact discoveries. These discovery some time with considerable controversy in the literature, sometimes at unusually impoliteand unprofessional levels. Some time artifact discoveries also surprised the world of science.
1) Different groups presents different results on same material and trying to prove each other results as wrong. Is it not sicietificy sound if these groups exchange specimens before they claim the work of others is simply wrong?
2) In some cases materials have been considered to be with ground breaking discovery when the data can be interpreted more simply via other well-known mechanisms. Is it not import to look wider before claims a breakthrough discovery?
3) In some cases the experimental results are true, despite theory implying that this is not possible. Is it appropriate to reject a experimental output just because theory doesn't exits which can explain it?
4) Controversy and attention on a new anomalous phenomenon such as Room Temperature Superconductivity.
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You are right Dear Prof. Aga Shahee. Anyway, thank you so much.
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I am following Sun et.al's well known procedure. There are times when I get a mix of this colloidal sticky emulsion (as I call it) and proper precipitated MNPs, but sometimes all I get is the sticky emulsion. What am I doing wrong?
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If you perform decomposition of the complex in diphenyl ether, then your problem is not. 5 nm nanoparticles are formed.
Roca A.G., Morales M.P., Serna C.J. Synthesis of Monodispersed Magnetite Particles From Different Organometallic Precursors // IEEE Trans. Magn., V. 42. P. 3025 – 3029
Hence your problems arise from alcohol. The complex is chiral. It has in solution two optical isomers and a racemic mixture. Together with adsorption on nanoparticles during decomposition, it forms
complex mixture with high viscosity.
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If I do MFM paramagnetic thin film patterned on SiO2, will it give a phase difference like ferromagnetic films?
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We know that by drawing a magnet close to a closed circular circuit, a current in the circuit is induced. Why? (I don't mean the mathematical description or the law of Faraday's induction, what is the cause of physics? What causes electrons to move?)
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Answer : As the magnet approaches the ring, the distribution of the magnetic field around the ring changes. Changing the distribution of the magnetic field around the ring leads to the generation of an electric field (on the ring plate). This electric field can change the distribution of ring electrons. Changing the electrons of the ring can create an induced potential in the ring circuit. The induced potential generated in the circuit circuit generates the induced electric current in the circuit circuit. (You can track the appropriate calculations from Maxwell's equations (especially the third and fourth equations)) Hope you got the answer right.
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I have obtained samples with ferromagnetic behavior (presence of Ni predominantly in the metallic state over the alumina surface) and paramagnetic (in which Ni is oxidized in NiO form is alumina surface) and, coincidentally or not, ferromagnetic samples seems to show greater interaction (stronger "bond") between Ni and Al2O3 than paramagnetic samples.
Is there any relationship between the magnetic behavior of the active phase of the catalyst (in my case, Ni) and its interaction with the oxide support used?
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Thank you very much Professor Marco Aurélio Suller Garcia
I share the same feeling as you.
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As known, the energy gap in the magnetic material emerges below one certain of temperature. In the literatures, some authors said energy gap is mainly induced by the orbital ordering/structural transition and other authors said the energy gap is induced by the single-ion anisotropy due to the change of the spin ordering. I am totally confused about the intrinsic origin of the energy gap.
Is the energy gap in the spin wave only ascribed to the different spin ordering or orbital ordering, or both? It seems that in some systems, the emergence of energy gap depends on both via spin-orbital coupling.
Can anybody give me some advice and clarify this point?
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Dear Prof. Qiang Zhang
In addition to all interesting answers of this thread, you can check the following reference [1] for the basic theory of spin waves & magnons---using the equation of motion of the magnetic moment--- in ferro & antiferromags.:
  • A magnon is a wave of the nonuniform precession of atomic magnetic moments in ferro & antiferromagnets according to [1] ch VII.
  • If there is no an external field H in ferromagnets, there is not gap in the magnon spectrum epsilon(k)---when only exchage interaction is taken into account pp. 286, please see eq. 70.3 for spin waves & 70.4 for magnons in reference [1]
  • If the oscillations of the intrinsic magnetic moment M are taken into account, those oscillations generate a magnetic field h & it has to be taken into account in the magnon description & then, a gap appears in epsilon(k) eq 70.10 pp. 292 in [1] is calculated for an easy axis of magnetization & an uniaxial ferromagnet.
  • If magnetic anisotropic is taken into consideration, then a gap appears in the spectrum (see for the case of ferromag eq. 70.12 pp 293 & for the case of antiferromagnets pp. 313 eq 74.12 [1] (Prof. Ch. Kittel 1951 result).
[1] Statistical Physics Vol 2 by E. Lifshitz & E. Pitaevskii ch VII Magnetism, Pergamon 1980.
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Ferromagnetic ordering breaks the time-reversal invariance irrespective of nature and type of ferromagnetic ordering. Does anti-ferromagnetic ordering also breaks the time-reversal invariance irrespective of nature and type or one can observed breaking of time-reversal symmetries in some AFM state (Like Neel State) and its preservation on other states?
In AFM state, is staggered magnetization only responsible for time revers symmetry breaking or any other intrinsic effect can also lead to time revers symmetry breaking?
In the ferromagnetic state, where the magnetic moments have spontaneously chosen to point in one particular direction, time reversal effect inverts the magnetization, so it would have a microscopically-observable effect. We thus say that ferromagnetism breaks time-reversal symmetry. What about AFM (M =0), is time-reversal symmetry broken in all case just because of change of sign of their staggered magnetization due to time reversal effect or time-revers symmetry breaking will depend upon type and nature of AFM state.
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Dear Prof. Aga Shahee
To my knowlegde the expression for the free Gibbs energy in antiferromagnets is given approximately by the following expression Eantif , and it has to be time reversal invariant always---pp. 25 & 170 in [1] & also pp 167 in [2].
Eantif = a M1.M2 - 1/2 b [(M1.n)2 + (M2.n)2] - (M1 . M2).H (*) where a is the exchange constant & b is the anisotropy constants, n is the anisotropic axis, H the external field & M1 & M2 the magnetization vectors which are given by the sum of all magnetic dipoles inside the sublattices of the antiferromagnet (*) pp. 250 of [1]
I quote Profs. Kaganov & Tsukernik book pp. 25 & 170-171:
"...The energy cannot change sign under time reversal (in these cases energy is said to be invariant under time reversal) This is clear from the expression for the ellergy of a free particle E = mv2/2. Under the reversal: t ---> - t & the sign of the velocity v is reversed, while that of v2 is not..."
[1] M.I. Kaganov & V. M. Tsukernik, "The Nature of Magnetism" Science for everyone, Mir-Moscow, 1995.
You can also check:
[2] Eletrodynamics of continuous media by Acad. L. Landau & E. Lifshitz, ch V-#48 pp 167, eq 48.2, Pergamon 1984. They use the phi thermodynamic potential free energy.
CC. Prof.
Behnam Farid
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Conventional superconductors are robust diamagnets that expel magnetic fields through the Meissner effect. It would therefore be unexpected if a superconducting ground state would support spontaneous magnetics fields. Such broken time-reversal symmetry states have been suggested for the high—temperature superconductors, but their identification remains experimentally controversial.
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Dear Prof. Dinesh Kumar Dixit
In addition to the interesting answers in this thread, I would like to add that: "broken time reversal symmetry state mean in case of unconventional superconductors" the following:
  1. For a substance (3He liquid isotope- phase A1 which has an splitting of T as a function of pressure P, tetragonal strontium ruthenate & hexagonal uranium platinum 3) to have time reversal broken state it has to be a cooper pair with expectation mean spin & angular values, both different from zero)
  2. K-time reversal operator theory for spin 1/2 particles is described in Prof. A. Messiah Quantum Mechanics ch XV, pp. 669-670 (eq XV-85) Dover, 1999.
  3. These three substances split the transition temperature Tc: under pressure the A1 3He phase & under stress the Sr2RuO4 & UPt3 superconductors, which for all indicate (is a signature) of a time symmetry broken state.
see please:
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I am following the below method so far & need guidance to further modify it:
1) Making a specimen
2) Making an Electromagnet using prepared specimen
3) Using DC & AC Source to find BH- Curve
4) Calculate Permeability from graph by taking respective points
Please make your suggestions regarding all 4 points
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It all depends on the parameters...what are you REALLY interested in..the field vs current ar one point..the field homogeneity..saturation properties etc etc..you may find a lot of hint in the IMMW proceedings (Intl magnet measurement workshops)and Also on the JACOW pages as well as in the CERN library ...CDS CERN..(all public access with free downloads.In addition you may look into the CERN accelerator school proceedings for magnetic measurements (via CDS CERN)
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I have sputtered a film which is used for magnetic tunnel junction. The insulator layer is 2.5nm MgO. Does anyone have an idea on how to measure the film TMR or RA value? I know that there is a kind of CIPT method, but we are not able to do that in this way. Does anyone know some other experimental methods?
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Another possible way is to cover part of the film with some sort of polymer or tape and mill the remaining part or perform selective wet etch.
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As intended composite is novel, so I want to know is it possible to calculate magnetic values by placing it's sample in some solenoid. Where I want to check magnetic field strength by changing current values.
Also, I want to inquire about possible simulation based (if any) or experimental methods.
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yes, sir, according to my knowledge
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I am making some magnetic tunnel junctions, but I always get the junction shorted. I am not sure whether the quality of MgO is good. Does anyone know how to check the quality of MgO? Such as AFM and XRD? Thanks.
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DO AFM for checking out the microstructure. Make sure that it not porous. Secondly, check the breakdown field of MgO. If you apply the electric field higher than that then film resistance becomes very small and it short circuit the device. In that case, you have to increase the thickness of MgO or lower applied voltage. Most important is film porosity must be minimum. Check this out. I hope it will solve your problem.
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I have just fabricated a magnetic tunnel junction with MgO insulator layer. How to check that it is shorted or working? Just simply apply a large current or voltage to break MgO in order to see resistance drop? What is the typical threshold value of the current and voltage?
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Dear Jiacheng,
by measuring the J-V-characteristic (I attache the model of Simmons) it could be possible to get a result. For a tunnel junction you have in rough approximation an exponential relation between current and voltage (some volts are enough). Higher fields destroy the barrier. If the relation is linear, you have a normal resistor. Because you expect insulating behaviour, the barrier then is shorted.
With regards
R. Mitdank
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I am looking for a circuit which can generate an emf oscillating at frequency of 2.5Ghz.
My setup is in such a way that, I am passing particles (negligible mass) from a tunnel and want an emf perpendicular to the flow. The emf should have frequency of 2.5Ghz
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Adding to the colleagues above there are many structures of the such oscillators where they can be built from discrete elements using one transistor such as colpitts oscillator or integrated oscillators with controlling voltage to tune them.
I would propose that you use an integrated voltage controlled oscillator at 2.5 Ghz. You can search the web for data sheet. If the output power is not sufficient to drive your load then you can use a class E or F amplifier tuned at the 2.5GHz .
If you want crystal stability you can use an frequency synthesizer FS with crystal reference as George hinted.
Best wishes
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A transition from ferromagnetic structure to flat spiral structure was observed in a groups of transition metal alloys. The space group is Pnma and the magnetic Mn atoms occupy 4c position. How to understand the occurrence of spiral structure in such compounds?
It is know that Dzyaloshinskii-Moriya interaction due to spin-orbit coupling is responsible for the spiral structure in some multiferroics oxides. However,  this interaction just occur in the sample without centrosymmetry. In my sample, the Pnma structure is centrosymmetric, and this interaction cannot occurs. Is there some other interactions or models to explain the spiral magnetic structure in centrosymmetric transition metal alloys?
For transition metal alloys, the interaction should be itinerant or direct interaction?
Sometimes, the electrons localize and delocalized partially. In this case, should the interaction be RKKY?
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We are sharing some thoughts on this question in a preprint coming in a few days. In short, magnetic frustration is enough for sprial (or even skyrmion) formation in centrosymmetric systems; and in particular, RKKY is a typical mechanism for realizing such sprial orderings.
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Iron meteorites cool in space in several milli or micro kelvins per years, so exsolution of Kamacite -Taenite along crystallographic axis generates these patterns. within a few million/ billion years. But is there any chemical additive or heat treatment possible that can do so within at most, a few days or weeks?
What can be practical uses of this kind of Fe-Ni alloys,like cheaper memory storage material?
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Actually Widmanstaten structure is an acicular metallographic structure resulting from a rather rapid cooling rate of iron base alloys. See : https://www.tf.uni-kiel.de/matwis/amat/iss/kap_8/illustr/s8_4_2.html
Logically you should be able to reproduce it in a lab, provided that the Nickel content is too high to stabilize the austenite at room temperature and provided that you know at which cooling rate you need to cool down the alloy from its austenitic state.
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We have acquired FMR curves dI/dH=f(H) for Fe3O4 superparamagnetic nanoparticles. I need to calculate their effective magnetic anisotropy Keff. How is this possible? Thanks in advance 
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@ Rasbindu V. Mehta can you please share the paper/method for calculating the effective anisotropy constant using field cooled and zero field measurements.
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Dear RG members,
I am calculating the MAE for 111 surface Slab of Fe2CoAl by following the examples in Quantum Espresso.I have found all the atomic sites MAE for Fe and Co sites in Al-terminal are out-plane. However, the total MAE for the same surface Slab of Fe2CoAl is in-plane.
Is it possible to have total MAE in-plane where individual atoms MAE out-plane?
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Hello,
Unfortunately, I have not any experience with type of calculation.
Best wishes
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How can I couple Electrical field and magnetic field from Piezoelectric and Magnetostrictive materials?
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You could make a expansioner/contractor that feeds into a piezoelectric charger, but it would operate at a very low voltage, so many would need to be series to get a charge, but still operate at a very low power, so many would need to be connected in parallel to power the battery.
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This might be a too general question, but:
In power electronics applications (such as DC-DC converters and such) and for switching frequencies of "a few hundred KHz", in general which one has lower core losses as a core of a power inductor (say for example an output filter inductor) : a "ferrite core" or a " powder core" ?
or is there any new material that can outperform those materials in terms of core losses (that can also handle power levels from a few kW to a few tens of kW)?
Thanks!
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The best cores for high frequencies are the ferrite cores because ferrites are electrically insulating. Therefore they will be no eddy current in the core. The limiting frequency is limited by the magnetization losses.
Ferroelectric based cores whether laminated or powder will still have eddy current losses but very suppressed. So, they normally used at lower frequencies.
As an advice you can survey the commertial coils that satisfy your requirements and specifications.
Best wishes
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I want to know about the material content difference in above material.
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AISI type equivalent of M15, M19 and M27 are ASTM equivalent of 36F145 , 36F155 and 36F175 respectively. They all are non-Oriented Electrical Steel Fully Processed
-M15 are available in two thickness(0.0140 inch, 0.0185 inch) with core loss of 1.45W/lb & 1.60 W/lb respectively
-M19 are available in three thickness (0.0140 inch, 0.0185 inch and 0.0250 inch ) with core loss of 1.55W/lb, 1.65W/lb and 2.0 W/lb respectively
--M27 are available in three thickness0.0140 inch, 0.0185 inch and 0.0250 inch ) with core loss of 1.75W/lb, 1.9W/lb and 2.25 W/lb respectively
Their main difference lies in core loss, thickness and application
Note: The core loss is calculated at 1.5T and 60Hz for above values
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I just started studying Zero-field splittings to understand the origins of magnetic anisotropy. So far, the concept of axial and rhombic anisotropic components are getting clear, but I still cant make sense of the meaning of a change in signal on the D component.
What happens if a have a positive D instead of a negative D?
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Depending on the sign of D you will stabilize different Ms levels. For negative D, the largest (+ and -) Ms levels will be stabilized, while for positive D, you will see a stabilization of the smallest Ms levels.
There are other repercussions of this change in sign, but much of the observed effects can be traced back to this fundamental change in ground state Ms levels. Hope this helps.
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how can I know if an electronic band is localized or delocalized in spin polarized DOS and PDOS schemes?
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Dear Moussouni Rebiha
From the density of states itself, one can not extract the information of the nature of the eigenstates (localized or extended).
You need to calculate either the inverse participation ratio or the typical density of states. Both contains the information you need, note that The typical DOS is a critical quantity in contrast to the averaged dos.
best regards,
G. Bouzerar
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How do you measure half metallic nature and the spin polarization of a ferromagnetic material?
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we calculated the energy difference between ferromagnetic and non magnetic states  of some half heusler alloys (by Wien2K). Now we are interested to calculation of curie temperature (TC) using the the energy difference between ferromagnetic and non magnetic states and mean field approximation.
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You can follow
DOI: 10.1007/s11664-018-6512-2
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Respected All! May I know the importance of large band gap in half-metallic compound? For example if Co2FeAl gives wider band gap in spin down as compared to Co2MnAl, what can be concluded? or What is the specialty of wider band gap compound over the low band gap one? Can we predict the efficiency of spin-injection or magnetic memory among these two compounds in terms of their spin band gap?
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I think, the materials have wide band gap is important when these materials are strained
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We know that magnetism can affect heat transport. Consider a forced convection problem where the heating fluid is water-based magnetite (Fe3O4) nanofluids. Fe3O4 nanoparticles have strong magnetic properties, so I wonder if these particles can control the heat flow? Is there any relationship between heat flow and magnetic interaction between nano-sized particles?
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Hi
Yes... There is a correlation between heat flow and magnetic attraction.... The induced heat may active the curie transition in materials.
Best
Arunprakash Vincent
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Hello,
The real problem is :
I have magnetic material (magnetized) that is deforming in time (let's say, because of vibration) with respect to the reference frame of the lab, I want to know, what is the induced EMF in a coil (stationary in the lab reference frame) ?
The simplified problem (see picture) :
I have two cases :
  1. The emitter is stationary and the receiver is moving (deforming)
In this case the induced EMF in the receiver is given by the general magnetic induction law ( A is the magnetic vector potential). Where fields are always expressed in the reference frame Ro.
2. The receiver is now stationary in Ro and the emitter is moving (deforming).
To keep things general the emitter is a deforming magnetic 3D body.
What is the induced EMF in the receiver coil ?
Thank you in advance.
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Work out how the flux through the receiver loop varies with time. This gives you d(PHI)/dt. You can get the flux variation from the change in shape and/or position of the metal core or the emitter, as Henri has already said.
To be exact there should be a minus sign in the equation, but for that to mean anything you need to know which direction is positive! To do that use Faraday's law and Lenz's law, but you probably don't need to know the direction of the current as it is ac from vibration.
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How the data read and write from a single tip having a spin valve structure?
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Deear Mr. Brajesh Kumar,
Hard disk drives are typically made up of ferro and / or ferrimagnetic materials. As a result the magnetic moments are tend to allign in a particular direction. when the external field is applied through the tip on the surface the spot , then the spot get magnetized in a particular direction which is different from the other spot where the magnetic moments are tend to orient in different direction. The spot where external field applied are the one's and the randomly oriented spots are zero's. Like wise the information of 1s and 0s are stored inside the hard disk drive. while reading the disc the spot will maximum magnetization will responds the external field and retrieves as 1s whereas randomly oriented moment does not responds to the external field and hence retrieve as 0s.
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Which procedure is better for superparamagnetic iron oxide nanoparticles sample in order to prepare the material for saturation magnetization measurement?
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Iam having trouble for the separation of magnetite nanoparticles from the solution stabilized by oleic acid. Is freeze drying a recommended technique for the separation of the particles?
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I have a problem, i need to synthesize magnetic activated carbon but the raw material is magnetite. So can anyone suggest me how to do it?
Because all i know to synthesize it i need to dissolve Fe, the co-precipitate it, and i don't know how to dissolve the iron in magnetite.
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The prepared PANI was added to Fe 2 O 3 nanoparticles (NPs) sol
in different concentrations (1%, 3%, 5% and 10%). The PANI incorporated
Fe 2 O 3 nanoparticles suspension was sintered at 100 °C in air
for 2 h for producing powder form. Thin films of pure Fe 2 O 3 NPs
and Fe 2 O 3 –PANI composites were prepared on corning glass substrates
by spin coating technique at 2200 rpm for 30 s and dried
on the hot plate at 100 °C for 10 min.
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I need to calculate force between two Permanent magnet (NdFeb) from different distance. .Size of two magnet is not same.
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Dear Enamul,
This is elementary. Need a ruler and a dynamometer.
Regards
Dr.Gedvidas
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I am trying to develop a magnetic thermal switch I need a material which has a curie temperature around 70-80deg Celsius.
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At one time, some ferrite materials (magnetic garnets or spinels) and amorphous magnets were developed for magnetic bubble technology, in which TC can be regulated within a very wide range by means of various substitutions. For your purposes, of course, alloys are more suitable. For example, TC can range from ~0 to 450 oC in alloys (Fe1-xCox)1-yMoy with x = 0.75-0.9, y = 0.1-0.2.
We are currently working with amorphous ferromagnetic microwires in a glass shell that have a Curie point ranging from room to ~150 oC. As an example, I will give the compositions of Fe3.9Co65B10Si12Cr9Mo0.1 (TC ~ 62 oC) and Fe5Co27.4B12.3Si12.3Ni43 (TC ~ 48 oC), in which the Curie temperature can be varied from 50 to 75 oC by means of heat treatment.
PS: To Carlos's answer_ In General (with the rare exception of multiferroics), ferroelectric crystals are not magnetic materials
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I'm trying to implement a uncompensated spins FM/AFM interface in a bilayers system that presents the phenomenon of exchange bias in Mumax, following the standard of the article "Modeling compensated antiferromagnetic interfaces with MuMax", however, I'm not succeeding. To implement uncompensated spins on the FM/AFM interface, do I have to define one or two AFM regions in Mumax? I tried to freeze the AFM layer with the "frozenspins" command but it did not work, can anyone help me with this problem?
Thanks a lot.
Oreci.
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Dear Yogesh Kumar,
You have to build two regions on Mumax R1 and R2 with different parameters.
R1 will be a cylinder and R2 will be a cuboid. Something like:
R1: = SetGeom (Cylinder (100e-9, 20e9). Trans (0.0, z));
R2: = SetGeom (Cuboid (400e-9, 100e-9, 20e9). Trans (0.0, -z));
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Is it possible to break a π bond between a solute and a magnetic solvent using magnetic force?
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yes, i think it is possible.
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Is it possible to break a π bond between a solute and a magnetic solvent using magnetic force?
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I believe yes, Amir hossein Aref it depends on what/which molecule you are considering. As for example if we consider weaker bonded CH3CL, in which C-Cl specifically. Then we can calculate the energy require to break this bond. Like for 9 debye the breaking energy lies near about 3.5eV.
So theoretically you can break these like weaker bonds using electric/magnetic force, And if you can build a machine which such capabilities you can also practically break these type of bonds.
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Consider a solution that one of it's components is sensitive to magnetic field. Is it possible to separate it by magnetic force? Or not? Is magnetic force strong enough to weaken the interactions between the components of the solution?
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The following article will be helpful for you.
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In case of single ion magnet, is there any way to correlate the magnetic exchange (ferromagnetic/antiferromagnetic) and AC magnetic susceptibility?
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Dear Ajit,
A magnetic ion hasn't ferromagnetic or antiferromagnetic order. That is to say, there are not a critical temperature as Curie or Neel although you have obviously exchange interactions or Coulomb associated to the electrons, but without interactions Weiss etc....
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Is anyone aware of cases where spin crossover critical temperature T1/2 does not match with DSC values (no structural phase transition). If yes, can you kindly refer to some published articles where T1/2 values are significantly different than DSC values?  I shall much appreciate this.
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Thank you so much @Dr. Juan Olguin for your answer.
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what are its applications?
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The calculation of the effective g-factor in semiconductors is important because of the dependence of the Knight shift on this quantity). It has received particular attention in view of its anomalous characteristic in the relativelynew semiconductors, namely the semimagnetic semiconductors or the diluted magnetic semiconductors ( dms) where the g-factors are found to be enhanced by two orders of magnitude with reference to the corresponding
ordinary semiconductors.
The concept of 'effective spin Hamiltonian' and effective g-factors was first introduced by Laura M. Roth,who obtained an expression for this factor, considering the antisymmetric part of the g-tensor, noting that the symmetric part vanishes for a crystal with inversion symmetry. Yafet obtained an expression for the square of the effective g-factor, by considering explicitly the spin-orbit interaction. Misra and Kleinman derived an expression for the effective Pauli spin susceptibility as a function of the square of the effective g-factor. They have shown the equivalence of their results with that of Yafet. While the effective Pauli spin susceptibility depends on the square of the effective g-factor, the dependence of the Knight shift on the effectiveg-factor is linear ( Tripathi eta11981,1982) Thus, the sign of the g-factor is ascribed from the sign of the Knight
Since the mean magnetic moments of the impurities are functions of temperature and change with magnetic field, in a dms the effective g-factor essentially depends on temperature, field and composition of the dms. Furthermore, the strong temperature and field dependence of the g-factor is believed to be responsible for the exotic temperature dependence of the quantum oscillation amplitude in the dms. In addition, most of the carrier-dependent magnetic properties of dms, which are important for spintronics, depend on effective g-factor.
References
1. A Green's function formulation of the k → · p → theory in the presence of spin- orbit interaction and magnetic field: Application to the electronic structure and related properties of w-GaN S. K. Shadangi, S. R. Mishra and G. S. Tripathi
J. Phys. Chem. Solids 122, 280 (2018):
DOI: 10.1016/j.jpcs.2017.09.031
2. Many-body theory of magnetization of Bloch electrons in the presence of spin- orbit interactions
G. S. Tripathi and P. K. Misra
J. Magn. Magn. Mater 322(2010)88
DOI: 10.1016/j.jmmm.2009.08.034
3. Theory of spin- EPR shift of Mn2+ in p-Sn1-xMnxTe
K. Dash and G. S. Tripathi
Semicond. Sci. Technol. 24(2009) 11504( 9 pages)
DOI: 10.1088/0268-1242/24/11/115004
4. Theory of photomagnetization of an interacting particle system: Application to
Hg_1-xMn_xTe
G. S. Tripathi ,B. G. Mahanty, P. Tripathi, S. N. Behera
J. Phys. CM 21(2009)056001
5. Spin-orbit and sp-f hybridization induced anisotropy of g-factors and effective masses in Pb1-xEuxTe
R. C. Patnaik, and G. S. Tripathi
Solid State Commun. 112(1999) 669
6. Theory of effective g-factors and effective masses in diluted Magnetic Semiconductors
R. L. Hota, G. S. Tripathi and J. N. Mohanty
Phys. Rev. B47(1993) 9319
7. Theory of effective g-factors in ternary semiconductors: application to Pb1-xSnxTe
R. L. Hota and G. S. Tripathi
J. Phys. Condens. Matter 3(1991) 6299
8. Theory of spin-orbit and many-body effects on the Knight shift
G. S. Tripathi, L. K. Das, P. K. Misra and S. D. Mahanti
Phys. Rev. B 25(1982) 3209, 1981
9. Spin-orbit effects on the Knight shift – A new contribution
G. S. Tripathi, L. K. Das, P. K. Misra and S. D. Mahant
Solid State Commun., 38(1981) 1207
10. Misra P K and Kleinman L 1972 Phys. Rev. B 5, 4581
11. Yafet Y 1963 Solid State Phys. 14, 1
12. Roth L M 1960 Phys. Rev . 188, 1534
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