Which of the following is most suitable for the core of electromagnets?

$A$ paramagnetic sample shows a net magnetisation of $6 \, A/m$ when it is placed in an external magnetic field of $0.4 \, T$ at a temperature of $4 \, K$. When the sample is placed in an external magnetic field of $0.3 \, T$ at a temperature of $24 \, K$,then the magnetisation will be $...... \, A/m$.

Explain hard ferromagnetic and soft ferromagnetic materials.

$A$ soft ferromagnetic material is placed in an external magnetic field. The magnetic domains:

Above the Curie temperature,the susceptibility of a ferromagnetic substance varies

The phenomenon of perfect diamagnetism in superconductors is called the . . . . . . .