CURIE - WEISS LAW IN FERRO MAGNETISM

Curie-weiss in ferro magnetism

Ferromagnetic substances follow curie Weiss law.
This law describes the change in susceptibility of
ferromagnetic substances with their temperature.
Susceptibility of a magnetic substance is equal to the
ratio of intensity of magnetization to the external field
applied when it is placed in an external magnetic field.
This is denoted by a symbol
χ = I / H
It varies with the absolute temperature of the magnetic
substance.

According to curie Weiss law the susceptibility of ferro
substances is inversely proportional to the absolute
temperature.
χ ∝ 1/ T
It is observed that above a temperature called curie
temperature susceptibility of ferromagnetic substance
will be very less and so that the ferro substance loses
its high intensive properties and behave as
para magnetic substance.
Curie temperature is denoted by Tc.

The value of curie temperature varies with the
substance.
Examples : for iron (Fe) Tc = 1040 K
Ni ------- 634 K
Cobalt (Co)--- 1394 K

The perfect expression for curie Weiss law is

χ = C / (T - Tc)
C is called curie constant.

It is observed in para magnetic substances which is
called curie law. Above curie temperature the
para magnetic substance behaves as dia magnetic
substance.
The graph between absolute temperature of
substance and its susceptibility for para , ferro and

antiferro materials is shown

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