Magnetic susceptibility of $Mg$ at $300 \ K$ is $1.2 \times 10^{-5}$. What is its susceptibility at $200 \ K$?

If $\chi_1$,$\chi_2$,and $\chi_3$ are the magnetic susceptibilities of a paramagnetic material at temperatures $T_1 \ K$,$T_2 \ K$,and $T_3 \ K$ respectively,then which of the following relations is correct?

$A$ sample of paramagnetic salt contains $20 \times 10^{24}$ atomic dipoles each of dipole moment $1.5 \times 10^{-23} \ J \ T^{-1}$. The sample is placed under a homogeneous magnetic field of $0.84 \ T$,and cooled to a temperature of $4.2 \ K$. The degree of magnetic saturation achieved is equal to $15 \%$. What is the total dipole moment (approximate) of the sample for a magnetic field of $0.98 \ T$ and a temperature of $2.8 \ K$? (Assume Curie's law).

Which of the following is the most suitable material for making a permanent magnet?

The magnetic property of a magnetic substance is associated with

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 :