1. Susceptibility ( m) of a
diamagnetic material is always negative. The relative permeability μr < 1.
Example For Cadmium, ( m) = - 0.18 x10-6
For Copper, ( m) = - 0.086 x10-6
For Silver, ( m) = - 0.2 x10-6
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1. Susceptibility (m) is positive and small.
Example For aluminum, (m) = 0.065 x10-6
For Calcium, (m) = 1.10 x10-6
The relative permeability μr > 1.
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1. Magnetic susceptibility value is large and positive.
The temperature dependence of susceptibility for ferromagnetic materials is
said to be complex.
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2. When magnetic field is applied, it repels the magnetic
lines of force. This property is exhibited by superconductors. Hence we call
all superconducting materials (at low temperature) as perfect diamagnet. When the temperature is increased beyond it
critical temperature, diamagnetism suddenly disappears and it behaves like a
normal conducting material.
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2. When magnetic field is applied to paramagnetic
material, it is attracted towards the centre of the
material.
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2. When magnetic field is applied
to a ferromagnetic material, the magnetic lines of force are strongly
attracted by the specimen.
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3. It does not depend on temperature and the strength of
applied magnetic field.
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3. Susceptibility is inversely proportional to absolute temperature of
the material. m α (1/T)
Curie’s law for high temperature m = (C/T)
T = absolute temperature in Kelvin; C = Curie constant
At low temperature m = C/(T-θ)
θ – paramagnetic curie temperature
θ is always very low. When the
temperature T < curie temperature, the paramagnetic becomes diamagnetic.
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3. Ferromagnetic materials exhibit hysteresis. Even if the magnetic
field is removed from the material, it retains the magnetism due to
spontaneous magnetization. They have permanent dipole moment.
4. The permeability of a ferromagnetic material is not a
constant, as magnetic induction (B) does not vary linearly with magnetic
field strength (H).
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4. No magnetic moment is present in the material.
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4. Spin alignment: All spins are randomly oriented.
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5. When the temperature of the ferromagnetic material is
greater than its Curie temperature, then ferromagnetic is converted into a
paramagnetic material.
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