Magnetic Materials and Magnetism

Magnetic Materials and Magnetism

  • Brian Ahern added an answer:
    Any advice on the Hysteresis loop and Permalloy ?

    Hysteresis loop of permalloy is very small and its related with losses. Magnetic Permeability of permalloy is very high and good heating can be obtained due to losses. Are there any other parameters that can influence the losses ?

    Brian Ahern

    The losses can be reduced to zero if one prepares a nanosintered ferrite block properly.  I have observed 5 deggrees C of cooling with barium Ferrite.

  • Gavin Abo added an answer:
    Is there any easy-to-make p-MTJ (Magnetic Tunnel Junction) recipe ?


    Can anyone recommend me a recipe for p-MTJ that is easy to make? Performance is not an issue, and it doesnt have to be novel design either.



    Gavin Abo

    Maybe you can use Sato and Kobayashi's metal mask process [ ].  It has been used to make magnetic tunnel junction (MTJ) having AlOx barrier and in-plane ferromagnetic layers [ ].  It might be possible to apply it to perpendicular MTJ (pMTJ), but I don't remember seeing any reports of it being successfully used for pMTJ.

    A semiconductor-based process is the standard process used to make pMTJ, which requires deposition equipment (usually a sputter system), etching equipment (usually an ion beam etching system also known as an ion milling system), lithography equipment (at least photolithography, but e-beam lithography is usually used too), and annealing equipment (usually a magnetic vacuum annealer [e.g., ]; though, it looks like someone else was able to do it with a heat gun [ ]). There is a stepwise planarization process that has been successfully used to make pMTJ at a university [ , , ].

    A five layer stack on top of a substrate might be the simplest for you to start with.  For example, a thermally oxidized silicon substrate, a bottom Ta seed and electrode layer, a CoFeB fixed layer, a MgO barrier layer, a CoFeB free layer, and Ta capping and electrode layer [ , ].

    I couldn't find any references, but I think CoFeB can sometimes be challenging to work with due to oxidization, stoichiometry, or some other problem(s).  If you instead used a Pd or Pt-based multilayer[ ], you should not have to worry about off-stoichiometry deposition, but using a multilayer may have its own challenges like the material (e.g., Pt) can be expensive to buy and interdiffusion between layers might be issues.

    • Source
      [Show abstract] [Hide abstract]
      ABSTRACT: We studied annealing effects on perpendicular anisotropy in CoFeB-MgO magnetic tunnel junctions. The results show that annealing is an effective method to improve the perpendicular anisotropy of a CoFeB-MgO system. It is found that a thicker CoFeB layer requires a higher annealing temperature to buildup its perpendicular anisotropy. However, perpendicular anisotropy could be seriously degraded if the annealing temperature is more than 350 °C. Our study suggests that CoFeB thickness should be optimized so that the required annealing temperature window for perpendicular anisotropy could match the annealing temperature for high magnetoresistance. In this work, the perpendicular anisotropy energy density of 2.5 × 106 erg/cm3 was achieved with tunnel magnetoresistive value exceeding 70%. The use of CoFeB films will enable the development of high density nonvolatile memory with size down to 30 nm.
      Journal of Applied Physics 07/2011; 110(3):033904-033904-4. DOI:10.1063/1.3611426

    + 1 more attachment

  • Titus Sobisch added an answer:
    Surfactant for stable suspension of fe-based alloy powder in a organic solvents?

    Is there a surfactant that is able to create a stable suspension of Fe-based alloy powder (particle size around 5 µm) in an organic solvent such as hexane, heptane or similar?

    Titus Sobisch

    nothing else is expected for high density particles of µm size in a low density, low viscosity fluid (Stokes law). Only solution microgravity.

  • Sunita Dey added an answer:
    Is there any possibility to convert scandium oxide to scandium nitrate?
    Please explain.
    Sunita Dey

    Dissolve Sc2O3 in quite excess of conc. HNO3 at 160-170 degree C for 30 minutes with stirring. Unlike other oxides, Sc2O3 need high temp and long time to form nitrates....

  • Kai Fauth added an answer:
    Is it important FMR and EDMR for caracterisation of MNP?

    Due to lack of equipment I dont think I will be able to perform ferromagnetic resonance, electrically detected magnetic resonance or Nuclear magnetic resonance spectroscopy in order to characterize my magnetic nanopaticles ( range 8-22 nm). what should I do? I only can use Vibrating sample magnetometer and MRI ( magnetic resonance imaging ).

    Do you think I will lack valuable data without those analysis or there are other methods to substitute them? for example site.directed spin labeling or electron spin resonance spectroscopy ( electron paramagentic resonance )

    Kai Fauth

    Diluting the sample will (in general) produce something threedimensional, whether spreading on a surface a two-dimensional array. For the same average distance between particles, you will have MUCH less sample in the latter case (the sample area in a magnetometer is limited). In the end it is up to you - it may or may not be easier to spread the samples on a surface than producing a threedimensional dilution. This depends on your system.

    In the 2D (surface) case, you have another nice check for interactions: With no interactions (and isotropic or statistically oriented particles), the M(H) curve will be independent of whether the field is applied within the surface plane or perpendicular to it. In the presence of dipolar interactions you will have in-plane-anisotropy (the equivalent of shape anisotropy in magnetic materials).

    In a case with about 15% surface coveragy by ~6nm Fe particles, we have easily observed such an anisotropy, see: hysica status solidi (b) 05/2010; 247(5):1170 - 1179. (DOI:10.1002/pssb.200945607).

    What the required distance actually is will depend on the moment of the particles. The larger the individual moments, the larger the required distance between them.

  • Tapan Chatterji added an answer:
    What is the difference between Morin transition and temperature induced spin reorientation transition?

    Basically, In both processes the direction of ferromagnetic vector spontaneously rotates from one direction to other. Here I'm concerning about the spin reorientation usually observed in orthoferrite systems which is a second order magnetic transition. Then what is the fundamental process of the spin flipping which makes Morin transition to be first order and different than spin reorientation?

    Tapan Chatterji

    Which orthoferrite are you talking of? HoFeO3 and TbFeO3 show spin reorientation transition and I studied them on single crystals by neutron diffraction. The other rare earth orthoferrite may also undergo such spin reorientation transition. You must note that the rare-earth orthoferrites have two magnetic sublattices, R (rare earth) and Fe. There are three different magnetic exchange interactions, Fe-Fe, Fe-R and R-R. Fe ions order at high temperatures of the order of 700 K. At lower temperatures spin the reorientation transition occur (for HoFeO3 T_R = 50 K). At even lower temerature rare earth ion orders. The three exchange interactions are of different magnitudes. Fe-Fe is the strongest, the Fe-R interaction is intermediate and R-R is the weakest. At high temperature Fe ions order due t the strong Fe-Fe nteraction. As the temperature is reduced Fe-R becomes gradualy more important causing soin reorientation transition and thn at very low temperatures the weak R-R nteraction causes ordering of the rare-earth sublattice. This is not a real spotaneous transition but can be called induced transition. This typical physics of two magnetic sublattices is common to RFeO3, RCrO3 and R2CuO4 (R = Nd). And this physics is quite different from the physics Morin transition in which Fe2O3 consists of one single magnetic sublattice.

  • Vincent Mosser added an answer:
    How can we 'flatten out' or reduce the noise in a Hall measurement setup?

    We are measuring the Hall resistance of a magnetic nanowire, the result shows that the different magnetization direction of the nanowire gives two different resistant value, as presented in the attached image.

    However as we can see that the 'on' and 'off' value is not exactly constant, they change all the time and we also see a lot of noise.

    Is there any electrical setup that we can add to the whole system so that the reading becomes a square wave?

    Vincent Mosser


    I agree with the previous answers. But, are you sure you are seing the effect of two magnetization states ? Or might it be the random telegraph signal (RTS) due to emission/capture of a single electron by a trap in your low-dimensional system? 

    We showed such signals occuring in quantum well GaAs-based Hall sensors, cf  the ref in the link. These are RTS signals and they look very similar to your signal. Depending on the charged or neutral state of a single trap, the current density distribution in the 1µm sized device is different, and the offset at the Hall output is different too.

    • Source
      [Show abstract] [Hide abstract]
      ABSTRACT: We report on studies aimed at understanding and improving the intrinsic noise of high-performance sensors using a 2D electron gas channel confined by a quantum well in the pseudomorphic AlGaAs/InGaAs/GaAs heterostructure. MIS gated and ungated Hall sensors shaped as a Greek cross with dimensions ranging from 100 mum down to submicrometer range have been investigated. At room temperature the predominant low frequency Hall voltage noise originates from the ensemble of trapping/detrapping events occurring within the continuum of GaAs surface states. Its power spectral density can be deduced from independent measurements of the interface trap density-of-states by applying Shockley-Read-Hall dynamics and the Fluctuation-Dissipation Theorem. In fact, theoretical spectra calculated without any adjustable fitting parameter coincide closely with the experimentally measured ones. At cryogenic temperature this interface traps noise freezes out, thus revealing a much weaker intrinsic background noise with 1/f spectrum. For small sensors the intrinsic /f noise converts into one or a few lorentzians due to the action of individual random telegraph signals (RTS). For Hall crosses with an intersection of 4x4mum2, we find statistically less than 1 fluctuator per each decade of time constant at 77 K. Due to the random distribution of the elementary fluctuators, some of these small Hall crosses may show less low-frequency noise than much larger 60x60mum2 sensors.
      Proceedings of SPIE - The International Society for Optical Engineering 05/2003; DOI:10.1117/12.497001
  • S. K. PARIDA added an answer:
    Why coercivity increase with thickness of magnets making a peak between 35-40 nm, then decreased?

    Why coercivity increase with thickness of magnets making a peak between 35-40 nm, then decreased?

    Using OOMMF programme.

    With dimensions (50/150) nm applied in external field.

    S. K. PARIDA

    magnetic anisotropy (directional dependence magnetic measurement) may be reason upto 40 nm, further deeper configurational anisotropy over take the peak width coercivity peak. 

    • Source
      [Show abstract] [Hide abstract]
      ABSTRACT: Cu/Ni thin films were deposited onto Si (100) substrate using high purity copper and nickel metals at room temperature. These films were found to be weakly ferromagnetic at room temperature as well as at low temperature of 5 K. Observed ferromagnetism is attributed to Ni layer as Si and Cu are diamagnetic in nature. The decreasing order of magnetization observed from ZFC measurements at around 40 K is attributed to the magnetic anisotropy. The difference in the magnetic behaviors of field cooled (FC) and zero field cooled (ZFC) measurements is also due to magnetic anisotropy. The Cu 2p core level in the interface region exhibits a large asymmetry on the high binding energy side compared to that of surface core level which indicates a charge transfer from Ni to Cu in the interface region.
      06/2014; 3(3). DOI:10.1166/mat.2014.1167
  • José Pérez de la Torre added an answer:
    How can I measure the size of polar nanoregion in the ferroelectrics near their para-ferroelectric phase boundary?

    Polar nano-region exists in the ferroelectrics undering the para-ferroelectric phase transition. The size of polar nano-region is in the range from 10 nm to 100nm. How to measure the size of them and also their evolution?

    José Pérez de la Torre

    I f the transition temperature is near room temperature a AFM , intermediate temperatures a photoelectron microscopy or others

  • Srikanth Chowki added an answer:
    In complex impedance spectroscopy, the graph Z'' vs Z' is generally described as a parallel connected RC circuit. How can one fit this graph?

    The Z'' vs Z' graph data is fit with using the parallel connected RC circuit. Can anybody explain this in detail..?

    Srikanth Chowki

    Thank you for your kind info..Raoul Rashid Nigmatullin 

  • Kundan Kumar added an answer:
    How to calculate lattice constant from XRD spectrum?
    Lattice Constant formula.
    Kundan Kumar

    go through this file and for more information please read Cullity book.

  • Valter Ström added an answer:
    Can I use a normal laboratory solenoid to investigate magnetostriction in mild steel using a strain gauge by measuring change in length?

    I am currently in my final year of bachelors and my research involves investigating the effect of an externally applied magnetic field on the young's modulus of a bar of mild steel. The problem is, I have not been able to get a solenoid to produce the magnetic field to investigate this phenomenon. My question is:

    1) will a normal laboratory solenoid allow magnetostriction in mild steel that can be measured using a strain gauge in terms of change in length of the specimen

    2) if not, what instrument can I use in order to produce the necessary magnetic field for this experiment. Where can I buy it.

    Thank you.

    Valter Ström

    Dear Huzaifa,

    usually magnetostriction is a pretty tiny effect, (it was a big hype when the Terfenol came 20 ys ago with so called giant magnetostriction) and I believe mild steel is in this category. Moreover, mild steel is certainly a soft magnetic material, and so would require only a modest field to reach saturation. Can you control the geometry of the sample? If so, a slender piece with a lengh/width (or whatever) ratio >10 would not need more than say of the order 10kA/m.... Possible with a solenoid even without an iron core.

    The tricky part is probably to quantify the elongation. One suggestion might be to use an AC field and detect the oscillating length at twice the driving frequency. This is due to the fact that magnetostriction does not sense in which direction the magnetization goes, right?

    How to detect this movement? I would refrain from a strain-gauge. Rather an optical method. Maybe an off the shelf little electronic LED-phototransistor device used in reading the presence of cards etc.

    This was just a few thoughts about your project!


  • Bindu K added an answer:
    How can I calculate the Hyperfine splitting and quadrupole splitting from Mossbauer spectroscopy?

    I have room temperature Mossbauer spectroscopy of ferrite sample with zero applied magnetic field. How to find out the hyperfine and quadrupole splitting from this data? 

    Bindu K

    Thank you Mr. Jerzy A. Sawicki. Can I get your e-mail ID Please. It will be helpful for me.

    Thank you Vishwajith and Goya

  • Abhay Singh Gour added an answer:
    How does magnetic pull measure between an Alnico disc magnet and Fe-Si steel at 4mm air gap?

    Magnet pull force is often measured between two magnets or a magnet with some reference sample. I would like to know a mathematical relation or the method to measure magnetic pull force between a Alnico magnet (disc of OD=40 mm, thickness 8mm) and Fe-Si strip (OD=40mm thickness 8mm) placed at a distance of 4mm apart. I also want to know what factors depends on magnetic pull measurement between two magnets.

    Abhay Singh Gour


    1) Connect your test sample to the weighing machine using hook. 

    2) Measure the reading W1 of the weighing machine.

    3) Fix the magnet sample on the lead screw made up of non magnetic material of 1mm pitch.

    4) Align the magnet on the lead screw with the test sample.

    5) Adjust the gap between the test sample and magnet as per your requirement by adjusting the height using lead screw.

    6) Note the weight W2 of the weighing machine.  


    where W1 is mg, W2 is mg+magnetic pull down force.

    Mag pull down force F= weight of the sample with magnet field- weight of the sample without magnet field



  • Tarik Ömer Oğurtani added an answer:
    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)?

    Tarik Ömer Oğurtani

    One write down the following global Helmholtz free energy which includes surface free energy associated with grain boundaries (GB).

    Global F  =  Vol.8{  Fs  3/R  +  Fb }   where   Vol= Np  (4 Pi R^3 /3)   Specimen Volume. Np  Number of grains,  R  mean grain size (radius),  Fs  specific surface energy of GB.  Fb  is volumetric Bulk Helmholtz free energy, which includes stored stain energy as well if any.

    Increase in  Sn concentration results segregation of  Sn at the grain boundaries, which may cause increase in the specific surface Free energy of grain boundaries, which may be compensated according to the above equation by   increasing  the grain size  R  to keep the global free energy invariant.

    The mostly there might be an upper limit for  the dopant concentration above which segregation may  be in the form second phase particles, which doesn't affect the specific surface energy any more. That is the case for  Ni doping in ZnS  system. 

  • Zubair Ahmad added an answer:
    What is the difference between HD and HDDR process used in preparation of powder for NdFeB magnet?

    Hydrogen decrepitation (HD) and  Hydrogen decrepitation deabsorbation recombination (HDDR) process is widely used in preparation of powder for NdFeB magnet. This process allow to crush strip casted material to powder ranging 250-300 micron meter size. The powder is then jet milled or ball milled to produce powder containing 10-15 micron meter size particle size.

    Zubair Ahmad

    Dear Prof. D. Fruchart, Thanks for nice comments and literature support. It is very useful for me and the research community as well. I still want to know which method is favorable and suit to produce laboratory scale and industrial scale NdFeB magnets, HD or HDDR.

  • Rajesh Babu Bitra added an answer:
    Can anyone explain how to calculate the composition of LaAlxFe12-xO19 (X=0.0-1)?
    How can we calculate amount of nitrates of lanthanum, aluminium and iron which is used to prepare LaAlxFe12-xO19 (X=0.0-1) and precursor is iron nitrate hexahydrate, lanthanum nitrate hexahydrate, Aluminium nitrate and citric acid.
    Rajesh Babu Bitra

    Edward is right. Be cautious while measuring if you are using hygroscopic chemicals

  • Victor Calvo-Perez added an answer:
    How can one distinguish superparamagnetic, spin glass, ferromagnetic from ZFC/FC DC magnetization data?
    (Hints: ZFC/FC data collapse at high field while show bifurcation in low field.)
    Victor Calvo-Perez

    Thanks Dr. Mehta, I get a magnetic material that it's ZFC/FC is quenched by a strong fields, May be I should elaborate the Xac separately.

  • Emir Acevedo added an answer:
    Does anyone have any data as to how the density and viscosity of different magneto-rheological fluids vary with the applied magnetic field?

    Density and viscosity data for different MR fluids would be very helpful. Any reference or papers would be helpful.

    Emir Acevedo

    You know if it is possible to model with any software , say , Ansys ?

  • Tejabhiram Yadavalli added an answer:
    Is there any method besides XRD and FTIR to find the amount of magnetite and hematite in an iron oxide sample?

    Magnetite- Fe3O4

    Hematite- Fe2O3

    Is there any method besides XRD and FTIR to find the amount of magnetite and hematite in an iron oxide sample?

    Tejabhiram Yadavalli

    XPS is a definitive answer. 

    I have never tried Mossbauer so I cannot comment on that

    VSM is reliable sometimes but i would not place my bet on it.

  • Bastian Henne added an answer:
    Does anyone have experience with feromagnetism in TM (Co, Ni) doped ZnO nanostructures and other Diluted Magnetic Semiconductor Oxides?
    Can anybody provide ideas about the specific experiments to support or identify the nature of magnetic interaction and required model to explain the ferromagnetic behavior in these materials? The different models as mentioned by the researchers are like (carrier mediated interaction, defect mediated interaction, Bound Magnetic Polaron model, Coey model, Zener model). But I do not have detailed ideas about the possible origin, So please help me regarding this 'with respect to the experimental findings'.
    Bastian Henne

    Maybe this paper comes in handy for you:

    Advanced spectroscopic synchrotron techniques to unravel the intrinsic properties of dilute magnetic oxides: the case of Co:ZnO

    A Ney et al 2010 New J. Phys. 12 013020


  • Ramanathan Krishnan added an answer:
    Why at curie temperature saturation magnetization become zero and above curie temperature magnetization appear again?

    In the curve for saturation magnetization v/s temperature for ferro and ferrimagnetic materials it is shown that at curie temperature saturation magnetization become zero and above that it becomes paramagnetic. 

    Ramanathan Krishnan

    Thank you Marek. Best regards.

  • Luiz Almeida added an answer:
    Who would want to cooperate with experimental results in a stochastic dynamical Preisach model for Barkhausen noise?

    I need cooperation on this theoretical work (it would be interesting to include some experimental results and additional suggestions before submission). It follows a preliminary abstract: 

    The Barkhausen Noise (BN) is attributed to a series of jumps in the magnetization of a ferromagnetic material when it is exposed to a varying magnetic field. When a coil is employed to capture the flux variation, these changes induce a voltage that may also be processed and transformed into acoustic noise. This noise manifestation has a vast practical application, especially for noninvasive material characterization techniques and their importance for understanding the relation to the magnetic domain scale. The aim of this paper is to propose an extend or modified Preisach model for magnetic materials. It is capable of representing rate-dependent hysteresis with macroscopic hysteresis loops. It also produces the time domain signal of the BN. The model is devised in a discrete N-dimensional state space form, where each hysteron is not confined to only two possible amplitudes and is also associated with a second-order dynamical system. The global model order and statistical distribution of the corresponding parameters define the temporal and spectral features of the noise signal. These parameters may also be related to microstructural properties or stress. This proposed hysteretic-stochastic dynamical model may simulate the response to arbitrary magnetic field signals over an entire hysteresis cycle and provides a platform for developing theoretical and practical studies of rate dependency and BN.

    Luiz Almeida

    Dear Kai,

    Thanks for sending the link and your valuable comments.

    Yes, "dynamically" include the field sweep rate, which changes the BN and the hysteresis shape. Since the model comprehend stiff systems, it requires stiff solvers and it is working at acceptable computational cost. Classical Runge-Kutta integration may not apply.

    I do not intend to deal with interactions between the domains. They are represented by individual modified Preisach operators.

    The spectral representation of the noise I am currently obtaining with this model is pretty close to those presented in the literature. So I believe the proposed approach can adequately be done with a purely statistical (dynamic) approach. In fact, the way it is devised, the model may be interpreted as a result of the Karhunen–Loève theorem and Wiener process, under the framework of Itô calculus.

    Hope to have made your questions clear.


  • Pedro Gorria added an answer:
    Bohr magnetons
    How to calculate the value for Bohr magneton per formula unit? I have got the value of saturation magnetization in emu.
    Pedro Gorria

    Dear Alejandro,

    You don't need the value of the applied magnetic field for the calculations. However, the value of H has to be large enough to reach the saturation regime for the magnetization. Anyway, to get the value of Ms as accurate as possible a law of approach to saturation (see Cullity or our recent paper in JMMM) must be used for the fit of the M(H) curves. The value of Ms is not that corresponding to the maximum applied field.



  • G. A. Levin added an answer:
    What load can a superconductor hold?

    If a superconductor is placed in a magnetic fields of permanent magnets, it levitates, an effect called Meissner effect. Can anyone describe what force the superconductor and the permanent magnet can oppose till they come in contact.

    what are factors on which the separation between the superconductor and the magnet depends?

    can anyone give the formula for force acting between them?

    G. A. Levin

    I regret to say it, but the previous answers are mostly wrong. When it comes to type II superconductors, the Meissner effect has nothing to do with the levitation phenomenon you described. A magnet can be suspended below a superconductor. The force between a permanent magnet and type II superconductor is neither repulsion nor attraction. It's a restoring force which appears due to Lenz law. The induced currents always oppose any change in external mag. field. The phenomenon is better called quantum locking. You can find examples on Youtube if you search it under quantum locking. Correspondingly, there is no universal formula. the force depends on geometry, critical current, relaxation rate, etc.

  • Fozia Aziz added an answer:
    Can cracks on thin film surface result in decrease of ferromagnetism?

    defects are found to change the physical properties of thin films. Is there an evidence showing decrease in ferromagnetism due to cracks on film surface. 

    Fozia Aziz

    well let me elaborate a bit what exactly I have observed. I have made films on different substrates with In as-deposited condition the compressive strained film had higher magnetization than the tensile strained films. When annealed in oxygen the ferromagnetism was suppose to increase but  I observed a decrease in saturation magnetization of annealed compressive strained films. When the AFM of the two films is observed the compressive strained films seems to have develop too many cracks on annealing but no such cracks are observed in annealed tensile strained films. Though this cannot be the only reason but still I wanted to know whether cracks can play a crucial role in decreasing ferromagnetism of material.

  • David Gray added an answer:
    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).

    David Gray

    Marek,  I don't think my external field will be that high - lest than 1T.  So, in a narrow field range, of 0-1T, I'm looking for first order transitions from AFM to FM.  I need to avoid paramagnetic.  

    FeRh is a great option - except for the cost of the rhodium.  I'm looking into some of the other systems, but I'm looking for a transition temperature in the 270-370K temperature range.

  • Raj Kumar added an answer:
    How can we tell from an M-H curve that the sample is superparamagnetic?
    Is it necessary for the coercivity to be zero for a superparamagnetic nanoparticle or may it be positive?
    Raj Kumar

    Dear Professor,

    My curve obey superparamanetic behavior from RT sample, I repeated VSM analysis for same sample but Ms - value for saturation is not completed.  What can we say if it so. 

  • Titus Sobisch added an answer:
    What is the effect of magnetic field on alignment of ferro fluid droplet ?

    I would like to receive comments on the alignment of ferrofluid droplet with an effect of magnetic field [ kindly check the attachment ] . For same quantity and same magnetic field , distance the ferrofluid droplet of different particle size exhibits different pattern , smaller particle size tends to accumulate more closer [ Fig.a ] , with increase in particle size , it tends to spread out [ Fig. b ] , with an effect of surfactant for smaller particles , it tends to spread in larger area [ Fig.c ] and if the magnetic field is moved then accumulation is towards one point leaving behind some particles away from magnetic field [ Fig.d ] , can somebody explain the relation between the effect of magnetic field on various pattern for particles with different size . need clarification on accumulation , spread out  w.r.t particle size and magnetic field. 

    Titus Sobisch

    It has to be added citric acid is no surfactant at all, i.e. it does reduce surface tension at higher solute concentration only by a few mN/m. It is a polar solute of low molecular mass.

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