Magnetic Materials and Magnetism

Magnetic Materials and Magnetism

  • Valter Ström added an answer:
    2
    Why can't I get high enough magnetic flux density in a solenoid with iron core (99.8% Fe)?

    I am trying to get about 1200 Gauss in a solenoid with a iron core (99.8% Fe).

    A radius of my core: 9 cm,

    A length of my core: 5.5 cm.

    Current: 3 A

    And I densely wound a 1mm-diameter copper wire (enamel-coated) around the core.

    Total turns of wire: 50 turns.

    I got around 10 Gauss at the center of the solenoid without the core, however only 120 Gauss has been measured at the center of the solenoid with the core.

    What would be the problem? Initial relative permeability of pure iron (99.8% Fe) is around 150, so I think over 1500 Gauss should be measured for my experiment conditions.

    I don't think insufficient magnetic field strength (H-field) applied by the solenoid can be a problem. According to my precise calculation, with the conditions written above (also assuming initial relative permeability of pure iron is 150, and B-H curve is linear in a B-field range of interest), a magnitude of H-field is around 700 A/m at the center of the solenoid, which is almost same as a magnitude of H-field (800 A/m) required by the solenoid to induce 1200 Gauss.

    I also made some assumption that 'magnetic viscosity' can be a problem, so I applied constant magnitude of current: 3 A for over 30 minutes, but nothing did change.

    Is it just because the core is too thick to be fully magnetized? If it is true, please tell me the reason.

    Please help me out. Any helpful comments would be appreciated.

    Valter Ström

    Yep. Agree with previous speaker.

    Way, way too thick core. You cannot gain from the possibly high susceptibility of the iron. Magnetization will be dictated by the demagnetizing effect. A core with a length/radius ration of something like 10 or even 30 will help you; a lot.

    And, while being at it. For most practical situations, the weight of a useful copper coil ends up as roughly similar to the weight of the core. In your case you need to wind a much larger coil.

    Before winding the soil, you should check what power source you have so you can adjust the wire gauge accordingly.

    Cheers!

    Hope this helps

  • Sami Mahmood added an answer:
    5
    Is there any possibility to convert stainless steel into permanent magnetized material?

    Hello friends

    I want to magnetized the stainless steel permanently.  Is there any method/procedure for this? If there is any method available than please post the answer.

    Sami Mahmood

    Talking about stainless steel magnets, these are of poor quality compared to other commercial magnets such as Sm-Co, Nd-Fe-B, hexaferrite magnets and alnico. That is why the production of SS magnets was discontinued on commercial scale, although low carbon steels are soft and have some applications. Harder steel magnets which were used for permanent magnet applications have higher carbon contents, together with other elements such as tungsten and chromium. Cobalt addition increases the coercivity, but SS magnets remain inferior to other commercial magnets. If your SS is a permanent magnet material, then you can crush the as-cast ingots into fine powder, compact it, and sinter. Then you should apply a field which carries the magnet into the saturation state, and remove the applied field. This will produce isotropic magnet. Due to the poor magnetic properties, however, the magnetization of this magnet can be removed by relatively small stray fields. If SS ribbons are fabricated, the use of a bundle of magnetized SS strips or needle-shape pieces can enhance the capacity of the magnet.

    Magnets can be also produced by aligning the particles in a field during the compaction process. This will result in better magnetic properties. Bonded magnets can also be produced by mixing with a polymer or rubber, and curing. So, the answer to your question depends on the type of steel you have; if the steel is magnetic, you can magnetize permanently   

  • Ariadne Tsambani added an answer:
    2
    How do you derive force calculations from induced currents in COMSOL AC/DC FEA?

    I have a model in COMSOL where a moving magnet induces eddy currents in an aluminum track. I have been able to successfully plot the currents themselves, but am unsure as to how to go about deriving magnetic force values from these currents.

    I tried implementing COMSOL's recommended Lorentz Force calculation, but the numbers it outputted were ridiculous. Also, nowhere in the Lorentz Force calculation did it seem to use the induced currents themselves. This was further evidenced by my removing the aluminum track from the model, effectively removing induced currents from the picture. The values outputted by COMSOL's Lorentz Force calculation remained the same. These factors indicate to me that the Lorentz Force option is not the correct approach.

    Any ideas or help in any way is gladly appreciated!

    Ariadne Tsambani

    Good Evening. Please find attach the link. Kind Regards Ariadne Tsambani

  • Valter Ström added an answer:
    2
    If the magnetic material into the cell, how to measure the cell magnetic, for example, I don't want to dry cells, how to measure?

    If the magnetic material into the cell, how to measure the cell magnetic, for example, I don't want to dry cells.

    Valter Ström

    Many magnetic measurements lacks proper quantification. If your determination should have a proper one, I believe you have to sacrifice some cells.

    Consider the following. Make a good accurate magnetic measurement. Saturation, coercivity etc, on a 'live' cell sample. After that, go to the thermogravimetric balance and burn off all organics. If you stay below ca 500C (check with literature) in an inert atmosphere, the remainings should be tha magnetic oxide. At this pint you know the weight and could normalize it to the previous magnetic do.

    If you do the heating in air, the Fe3O4 might turn into Fe2O3, which means a slight weight gain... but could be calculated; however whether this oxidation is 100% effective is difficult to verify.

    Well, life's ...

  • Zhao Huang added an answer:
    3
    What does the 'broken time reversal symmetry state' mean in case of unconventional superconductors?

    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.

    Zhao Huang

    After dropping a common phase , the gap functions of S+- and S++ are real numbers which reserve the time-reversal symmetry.

    Time-reversal symmetry is actually the motion-reversed symmetry. In a system with a magnetic field, the reversed motion of an electron breaks the Newton law, and thus we call the time-reversal symmetry (motion-reversed symmetry) broken. Therefore the appearance of spontaneous magnetic field can be taken as a signature of broken time-reversal symmetry. The superconductors with complex gap functions can induce spontaneous magnetic fields at grain boundaries, thus relating the nontrivial phase with the time-reversal symmetry. Here is my understanding on the time-reversal symmetry at present. It is possible to have different understandings from other aspects. 

  • A.M. Lourenço added an answer:
    10
    How can I get a calibration standard for a Molspin Minispin Magnetometer?

    I work in a Lab of Rock Magnetism an Environmental Magnetism. The magnetometer calibration standard suffered some damage and needs to be replaced. Unfortunately Molspin Ldt was acquired by the Bartington Instruments, and this company no longer provide support or servicing for any existing products previously supplied by Molspin Ltd.The value of the standard in use was 562 mA/m. Can anyone help me to solve this problem?

    + 1 more attachment

    A.M. Lourenço

    Hi Habib!

    Thank you for your help. I'll follow your advice

    Best regards

    Ana

  • Richard Cselko added an answer:
    4
    Can the imaginary part of dielectric constant have negative values?

    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?

    Richard Cselko

    Perhaps you could let us know about the measuring system you are applying. 

    Kramers–Kronig relations might be of your interest.

  • Ftema W Aldbea added an answer:
    12
    What is superparamagnetics?

    Magnetic nanoparticles exhibit superparamagnetism how it is different from paramagnetism?

    Ftema W Aldbea

    Mainly superparamagnetism is occurred for grains with size less than 5 nm and its magnetic loop at room temperature is not saturated with zero coersivity (Hc=0). Also, the superparamagnetism can be defined by the magnetization of a grain of volume V = (5 nm)3 and anisotropy of 4 X 106 erg/cm3 is thermally unstable at room temperature. On the other hand, for particles whose radius is smaller than about 1 nm the external magnetic field is unable to produce saturation, because it cannot compete against thermal excitations. Note that true ferromagnetism is limited to infinite magnets, because thermal excitations in finite magnets cause

    the net moment to fluctuate between opposite directions and yield, ultimately, a zero spontaneous magnetization

  • Tanu Sarkar added an answer:
    18
    In an AFM/SG system showing exchange bias property, how can I confirm that the observed exchange bias is not a minor loop?

    In case of SG or FM clusters embedded in an AFM matrix the MH loop never saturates because of the presence of strong anti ferromagnetic interaction, then how genuine exchange bias property is defined, all can be think of minor loop as we are not getting saturation?

    or in that case how we will know the saturating field up to what we should measure the MH loop  to avoid the minor loop?

    Tanu Sarkar

    Dear all, Thank you for the valuable discussions

    about the saturation of ferromagnet, I have seen MH loops where the loop opening closes but magnetization increases.. in that case will the following be applicable to clear the confusion of the saturation of an mixed FM/AFM system??

    The law of approach to ferromagnetic saturation...

    M = MS(1−a/H −b/H2)+χH where χ is the high field susceptibility. as mentioned in Journal of Alloys and Compour, ds 260 (1997) 196-200 and also J. Phys.: Condens. Matter 21 (2009) 078002 (2pp)

  • Newt Ball added an answer:
    3
    How to measure magnetic field required to saturate ferromagnetic material?

     we need to know the field required to saturate the ferromagnetic sample like iron,nickel and ferromagnetic steels. what method will u suggest us to measure it. example VSM, but we don't have VSM facility. can u suggest  any other method?

    Newt Ball

    You are mistaken to think that you can make this measurement on a rod core.  Generate a closed magnetic path with nothing but the material to be measured.  Put two windings, linking the core.  With a sine wave source, drive one winding with a current, measured on the x-axis of an XY scope.  Integrate the induced voltage on the second winding and drive the y-axis of the scope with the integrated waveform.  The X-Y pattern is the hysteresis curve of the material, at the drive frequency.  The lowered slope of the curve at the tips, is saturation.  You get to create your own standard for slope reduction.  There is no industry standard.

  • Palash Gangopadhyay added an answer:
    18
    Does a MOKE signal always follow a magnetization curve?
    To clarify: does a MOKE pattern always match with a VSM / SQUID magnetization curve? Or does it also contain significant information about magneto optic transitions that could potentially alter the pattern? If so what are the ways to separate the two?
    Palash Gangopadhyay

    Ali, how does your phase (of Y) look like? 

  • João Azevedo added an answer:
    4
    Does anyone know an Aluminum etchant which does not etch Fe, Co and Si ?

    - Do need to remove 1 micron of Al without removing 250-500nm of FeCo, or 1 micron of amorphous Silicon. 

    João Azevedo

    Check link for possible solutions.

  • Alexander T. Morchenko added an answer:
    4
    Query about magnetic Heusler alloys?

    I am working with NiMnSn heusler alloys. I have produced powder samples by ball milling technique. The obtained powder was compacted to make pellet and sintering was done. Now I want to know, can I study mechanical properties (wear resistance, hardness etc.) of such pellet samples rather than magnetization study. Because I want to avoid magnetic studies. Kindly guide me whether it is worthy or not.

    Alexander T. Morchenko

    If You are not interested in the magnetic properties, You can not be explored them.

    But I believe that you are interested in the question: "… if I could ruin the samples before

    further study of the magnetic properties by my coworkers or other researchers?"

  • Jan široky added an answer:
    2
    How to calculate Dst index from X, Y and Z that i measured?

    Hello. I have measured Earth magnetic field and have now x, y and z axes values in nT. How to calculate Dst index from this data? Thank you!

    Jan široky
    Thank you Dennis!
  • Sree Ranjini Kizhakkethil added an answer:
    6
    How the remanent flux density of Samarium cobalt magnet vary with temperature. What is the equation involved?

    How the remanent flux density of Samarium cobalt magnet vary with temperature? What is the equation involved.If I have SmCo magnet having Br of 1.12T  at a temperature of 40 degress what will be the Br value at 100 degrees?

    Sree Ranjini Kizhakkethil

    Thank you  kai Fauth

  • Brian Ahern added an answer:
    2
    Can any one help me in clarifying my doubts in magneto-dielectric effect in BiFeO3?

    How the magneto dielectric coupling increases as the concentration of dopant increases in weak BiFeO3? What is the role of dopant in increasing the magneto-dielectric analysis?

    Brian Ahern

    All ferromagnets share the same molecular orbital topologies. Dopants can make local changes that induce a solid-solid phase change.

    The dielectric propeties are mostly a measure of electrical resistivity. The doppants may interrupt    electron transfer through specific orbitals..

    All conduction takes place within connected orbitals.

  • Yuri Mirgorod added an answer:
    4
    Can maghemite nanoparticles show any critical lowering of coercivity around a transition temperature like for magnetite (Verwey transition)?

    It is known that magnetite transforms from cubic to monoclinic structure at a transition temperature (Verwey transition, Tv), where magnetic anisotropy and resistivity change abruptly . In the temperature Vs coercivity plot this effect is noticeable, where a isotropy point (near to Tv) is observed, showing the minimum coercivity (even less than the room temperature value).  I have also observed this kind of coercivity lowering at 125 K for maghemite nanoparticles of around size 5 nm, while my sample has not shown any Verwey transition at M-T measurement and also ideally it should not show.  

    Yuri Mirgorod

     See my profile

    Yu A Mirgorod • V M Fedosyuk • S G Emelyanov. Iron Ore Concentrate for Purifying Water from Oil. Chemistry for Sustainable Development 20 (2012) 315-322 

  • Saravanan .l added an answer:
    16
    What is the relation between lattice constant and energy gap of the magnetic or non magnetic materials? Is any formula for that "a" and "Eg"?

    What is the relation between lattice constant and energy gap of the magnetic or non magnetic materials? Is any formula for that "a" and "Eg"?

    Saravanan .l

    Thanks for your reply

  • Charles Francis added an answer:
    99+
    Are magnetic and electric fields made by different photons?

    Quantum field theory tries to reduce the fields to particles (bosons) which interact with their sources (fermions) transferring energy and momentum, if we restrict to electrodynamics. In the case of the weak or strong nuclear interactions the gluons carry also color or flavour, that we can forget for the moment ,without entering in this question dtirectly, given its complexity.

    Considering only electrodynamics then, we know that a magnetic field cannot give energy to a free electron, while the electric does. Could we understand this different physical behaviour using a Feynman diagrams or the concept of photon-electron interaction instead of the field? How could we understand the change of "magnetic photons" by "electric ones" using the Faraday or Ampere's law? 

    Charles Francis

    Daniel, I have respect for science. I do not respect people like yourself who do not know anything of the subject and who use personal attack and accusations of ignorance to promote unintelligent and ignorant theories (such as the first part of your post). If you were not violating your own conditions, I would not treat you accordingly. For example, I have already given a full and polite answer to your question about neutrino mass. You have responded with accusations of idiocy and ignorance, and continue to show a lack of respect by refusing to acknowledge the answer and by repeating the question. Since your only purpose in posting is to reduce the level of discussion to below any acceptable level of intelligence, you are in no position to advise on what sort of response you deserve.  

  • Konstantin Guslienko added an answer:
    18
    Are there materials that exhibit magnetic transitions from antiferromagnetic to ferromagnetic?

    I am looking to see if transition between antiferromagnetic and ferromagnetic orders are possible.  I'm looking for something akin to the ferro-para transition at the Curie point.

    Alternatively, are there structures, such as exchange bias stacks that would allow for transition from an ordered ferromagnetic to another ordered state (either ferromagnetic with a different axis or antiferromagnetic).

    Konstantin Guslienko

    There should essential internal energy decrease in course of any AFM->FM transition increasing temperature because FM state has lower entropy in comparison to AFM one.

  • Guijiang Li added an answer:
    2
    Can we prepare SmCo5 using arc-melting furnace with high moment. I always get low moment with arc-melting method. What's wrong with this method?

    Anyone is welcome.

    Guijiang Li

     thank you very much.

  • Sami Mahmood added an answer:
    2
    What is the difference between Mn ferrite and other ferrites which saturation magnetization in Mn ferrite is higher than others?

    Based on my studies and reports in a lot of articles saturation magnetization of Mn ferrite is higher than other ferrites such Co and Fe. And I have never seen any result for this difference. 

    Sami Mahmood

    The question is not complete; one should specify the temperature at which magnetic measurements are carried out. At zero absolute temperature, the statement in the question is correct, but at room temperature, it is not accurate. The following data are available for the saturation magnetization (in emu/g units, which is an intrinsic property of the sample):

                                              MnFe2O4          Fe3O4         CoFe2O4           NiFe2O4

    0 K                                        112                      98                    90                      56

    20 C                                       80                       92                    80                      50

    μB/molecule(Calc)               5                         4                      3                         2

    μB/molecule (Meas)            4.6                       4.1                  3.7                     2.3

    The theoretical number of Bohr Magnetons/molecule for a collinear spin structure in inverse spinel is equal to the magnetic moment (in Bohr magnetons) of the Me (divalent) ion in MeFe2O4 spinel.   Notice that the number of Bohr Magnetons/molecule, μB/molecule (Meas), evaluated from measurements at 0 K is generally consistent with the theoretical value, except for Co-ferrites in which the orbital angular momentum is not completely quenched, and gives a contribution to the net moment, In addition, the discrepancy between theory and experiment could be due to the fact that the spinels are not perfectly inverse. Therefore, the saturation magnetization is generally magnetic structure sensitive. However, in the case of Mn-ferrite, the magnetic moment of Mn2+ is equal to that of Fe3+ (5 μB). The net moment per molecule, therefore, remains  5 μB (theoretically), regardless of the degree of inversion in the spinel.

    A note on the room temperature saturation magnetization:

    The Curie temperature for Mn-ferrite (300 C) is much closer to room temperature than Fe-ferrite (585 C), Co-ferrite (520 C), and Ni-ferrite (585 C). The saturation magnetization of Mn-ferrite falls off much faster with increasing temperature from 0 K to RT (by about 20%) than the other ferrites (which demonstrate ~<11% drop). The competing effects of higher saturation magnetization of Mn-ferrite at 0 K, and faster drop, leads to a RT saturation magnetization for Mn-ferrite lower than that of magnetite, and almost equal to that of Co-ferrite (where the faster drop of Mn-ferrite magnetization is compensated by its ~24% higher magnetic saturation at 0 K). The saturation magnetization of Mn-ferrite, however, remains significantly higher than that of Ni-ferrite, due to the fact that the saturation magnetization of Mn-ferrite at 0 K is twice as large as that of Ni-ferrite, which cannot be compensated by the faster drop in Mn-ferrite saturation magnetization as in the previous cases.   

  • Andrew O'Hara added an answer:
    1
    Curie Temperature Calculation by DFT/MD calculations (vasp)?

    How can we calculate curie temperature through vasp calculations? 

    Anyone can suggest how to initiate Monte Carlo simulations for curie temperature calculations for comparison?

    Andrew O'Hara

    One method for calculating the Curie temperature of a ferromagnetic using density functional theory is to construct model spin Hamiltonian to treat in terms of a mean-field type approach (in this case the Curie Weiss model). The model will be parameterized by J, the exchange constant between magnetic atoms (with different J's for 1st nearest neighbors, 2nd nearest neighbors, etc).  Essentially in this step, you would need to do DFT calculations for a variety of magnetic configurations and then use the energies to extract the values of J.  An example of this was done in the following paper for EuO and Gd-doped EuO:
    J. Lee, N. Sai, and A. A. Demkov "Spin-polarized two-dimensional electron gas through electrostatic doping in LaAlO3/EuO heterostructures," Phys. Rev. B 82, 235305 (2010)

    A more detailed description of how to construct the effective Hamiltonian and use DFT to extract the parameters can be found in Jaekwang Lee's dissertation in Chapter 5 (in particular sections 5.4.6 through 5.4.8 (p58-p64)).  The dissertation is available from the University of Texas here:
    https://repositories.lib.utexas.edu/handle/2152/ETD-UT-2010-08-2012

  • Saoussen Mahjoub added an answer:
    8
    How can one explain curvature in magnetization curves observed above the Curie temperature?
    M(T)-curves measured for sigma-FeV compounds exhibit curvature well above the magnetic ordering temperature (Curie point).
    Saoussen Mahjoub

    How can I fitted by Brillouin function !

  • Ashraf Ali added an answer:
    4
    Why does the grain size increase with Sn concentration in Ni-Zn ferrtie (Ni0.6-x/2Zn0.4-x/2SnxFe2O4)?

    ferrite magnetic materials Ni-Zn ferrite

    Why does the grain size increase with Sn concentration in Ni-Zn ferrtie (Ni0.6-x/2Zn0.4-x/2SnxFe2O4)?

    Ashraf Ali

    Dear Tarık Ömer Oğurtanı, thanks for your ans. also for your valuable time.

  • Brian Ahern added an answer:
    15
    I measured hysteresis loop for LiCd ferrite, but hysteresis loop showed a strange behaviour ?

    I measured hysteresis loop for LiCd ferrite, but hysteresis loop showed a strange behaviour: magnetization increased with applied field then when field increased magnetiztion started to decrease. what is this behaviour? why this happens?

    Brian Ahern

    Strontium ferrite has a most unusual loop when pulses rapidly. Any explanations would be helpful.

  • Adrien Bolens added an answer:
    3
    Are there any examples of Dzyaloshinskii-Moriya interaction in itinerant magnetic systems ?

    I'm thinking of a simple Hubbard model with the addition of the Dzyaloshinskii-Moriya interaction (asymmetric interaction of the form Dij⋅(SixSj) ) between the spins of the itinerant particles.

    Adrien Bolens

    Thank you very much for your helpful answers.

  • Tahir Nawaz Khan added an answer:
    28
    How to calculate lattice constant from XRD spectrum?
    Lattice Constant formula.
    Tahir Nawaz Khan

    Cullity book link : https://archive.org/details/elementsofxraydi030864mbp

  • Kai Fauth added an answer:
    8
    Did the electronic band structure change with temperature?

    in the base of DFT, the obtained band structure is at 0 kelvin.Now the band structure wouldn't change with temperature?

    Kai Fauth

    I don't entirely agree - in a ferromagnetic phase transition, participation of the lattice (via spin orbit coupling) is not essential to the fundamental change in electronic structure (lifting of spin degeneracy), e.g. within the simple Stoner picture [of course I do know that the full picture is generally not captured in this model].

    Also, when considering solids with strong variationss in the density of states (doped semiconductors being an example), changes owing to occupation statistics alone may bring about dramatic changes in electronic properties such as conductivity without a fundamental change in the underlying DOS.

    Otherwise, I do agree that it makes sense to distinguish cases with and without "participation" of the lattice [even though the lattice itself results from electronic interactions...].

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