Materials suitable for permanent magnets should have

Statement $I :$ The ferromagnetic property depends on temperature. At high temperature,a ferromagnet becomes a paramagnet.
Statement $II :$ At high temperature,the domain wall area of a ferromagnetic substance increases.
In the light of the above statements,choose the most appropriate answer from the options given below :

Curie's law can be written as

An example of a diamagnetic substance is

Give some examples:
$(i)$ Ferromagnetic substances.
$(ii)$ Paramagnetic substances.

The product of magnetic susceptibility $(\chi)$ and absolute temperature $(T)$ is constant for a