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.
In physics and materials science, the Curie temperature (Tc), or Curie point, is the temperature where a material's permanent magnetism changes to induced magnetism. The force of magnetism is determined by magnetic moments.
The Curie temperature is the critical point where a material's intrinsic magnetic moments change direction. Magnetic moments are permanent dipole moments within the atom which originate from electrons' angular momentum and spin. Materials have different structures of intrinsic magnetic moments that depend on temperature. At a material's Curie Temperature those intrinsic magnetic moments change direction.
Permanent magnetism is caused by the alignment of magnetic moments and induced magnetism is created when disordered magnetic moments are forced to align in an applied magnetic field. For example, the ordered magnetic moments (ferromagnetic) change and become disordered (paramagnetic) at the Curie Temperature.
Higher temperatures make magnets weaker as spontaneous magnetism only occurs below the Curie Temperature. Magnetic susceptibility only occurs above the Curie Temperature and can be calculated from the Curie-Weiss Law which is derived from Curie's Law.
In analogy to ferromagnetic and paramagnetic materials, the Curie temperature can also be used to describe the temperature where a material's spontaneous electric polarisation changes to induced electric polarisation or the reverse upon reduction of the temperature below the Curie temperature.
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In any magnetic materials there exists different temperature dependent magnetic phases which try to collectively (moments) orient (change direction) with the applied magnetic field. In such a situation, say for an example the orientation of the collective magnetic spins from random order to definite order has to pass through a state where the magnetization of the exchange interactions becomes nullified. After gaining its intrinsic energy in a path of collective orientation to definite order the magnetization reappears. But remember these are all governed by temperature and the applied magnetic field, which plays important role in defining the magnetic phases.
For a definit answer you have to tell someting about the materia you investigate!!l
The material is Mn doped Cobalt Ferrite. But the question is far more general.
Dear Kumar above Tc the macroscopic magetims disappear, and Curie law isobserved. However you should study the effect at remanence (Happ=0). Another microscopic techique as Mossbauer spectroscopy is useful . The XDR is useful also but if you have various phases is very dificult. In the doped Mn spinel pay attention to the oxidation number of Mn
IN order to determine the Tc one has to apply minimum mag field. Above Tc if sufficiently large magnetic field (1 or 2 teslas) is applid then forced magnetism will appear. This is because the applied magnetis field energy wins over the temperature effects. This is true for all magnetic material.
Above the Curie temperature, the ferromagnetic material become paramagnetic. But if you do the experiment in the Earth magnetic field, there is a induced magnetization. You can do the experiment in a magnetic shielding to prevent the Earth magnetic field influence.
Remember the influence of the earth's field which is about 0.3 Oe would matter only in some very special very low Hc (amorhpus alloys) material. And this effect would tend to align the moment when the material cools below Tc. Remember that that is how one found the reversal of earth's field. That is another subject altogether.
Dear Ramathan: Above Tc the material become paramagnetic(superparamagnetic), so if there is some magnetic field it make the effect of align the magnetic moments and there is an induced magnetization. It is the definition of paramagnetism. When the ferromagnetic material cool below Tc, then a remanent magnetization is present.
I agree. This field if powerful enough would naturally win over the Thermal fluctuatins. But this is not a natural situation. Abiove Tc ferriomagnet will turn into para or let us say lose its spontaneous M. Application of field is a perturbation.
One should distinguish saturation magnetization from spontaneous magnetization.
Yes of course. Spontaneous M is the M at H=0. Saturation M is the extrapolation for highest fied used to measure.
Ramananthan, my comment was concerned first of all with formulation of the original question, by no mans with your answer(s). Have a nice day!
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