Question

Which magnetic material obeys Curie's law in which the magnetic moment is localized at the atomic or the ionic sites where there is no interaction between neighboring magnetic moments?
1. Diamagnetic Materials
2. Paramagnetic Materials
3. Ferromagnetic Materials
4. Anti-ferromagnetic Materials

Answer 1

Correct Answer - Option 2 : Paramagnetic Materials

Paramagnetism:

• There are several theories of paramagnetism, which are valid for specific types of material.
• Langevin's model, which is true for materials with non-interacting localized electrons, states that each atom has a magnetic moment that is randomly oriented as a result of thermal agitation.
• The application of a magnetic field creates a slight alignment of these moments and hence a low magnetization in the same direction as the applied field.
• As the temperature increases, then the thermal agitation will increase and it will become harder to align the atomic magnetic moments and hence the susceptibility will decrease.
• This behavior is known as the Curie law and χ = C / T, where C is a material constant called the Curie constant. 
• Materials that obey this law are materials in which the magnetic moments are localized at the atomic or ionic sites and where there is no interaction between neighboring magnetic moments.
• The hydrated salts of the transition metals, e.g. CuSO₄·5H₂O, are examples of this type of behavior as the transition metal ions, which have a magnetic moment, are surrounded by a number of non-magnetic ions/atoms, which prevent interaction between neighboring magnetic moments.