Ferromagnetic materials used in a transformer must have

When a magnetic substance is heated,then it

$A$ sample of a paramagnetic salt containing $3 \times 10^{24}$ atomic dipoles each of dipole moment $2 \times 10^{-23} \text{ A-m}^2$ is subjected to a uniform magnetic field of $880 \text{ mT}$ and cooled to a temperature of $3.5 \text{ K}$. The degree of magnetic saturation achieved is $10 \%$. If the sample is subjected to a magnetic field of $990 \text{ mT}$ and cooled to a temperature of $2.1 \text{ K}$, then the total dipole moment of the sample is (in $\text{ A-m}^2$)

The susceptibility of a magnetic material is positive and small. The material is

$A$ paramagnetic sample shows a net magnetisation of $8 \text{ Am}^{-1}$ when placed in an external magnetic field of $0.6 \text{ T}$ at a temperature of $4 \text{ K}$. When the same sample is placed in an external magnetic field of $0.2 \text{ T}$ at a temperature of $16 \text{ K}$,the magnetisation will be

What is a diamagnetic substance?