The only property possessed by ferromagnetic substances is

In the hysteresis cycle,the value of $H$ needed to make the intensity of magnetisation zero is called

The $B-H$ curves $S_1$ and $S_2$ in the adjoining figure are associated with:

The figure shows the experimentally measured $B$ vs. $H$ variation in a ferromagnetic material. The retentivity,coercivity,and saturation of the material are,respectively:

Answer the following questions:
$(a)$ Explain qualitatively on the basis of the domain picture the irreversibility in the magnetisation curve of a ferromagnet.
$(b)$ The hysteresis loop of a soft iron piece has a much smaller area than that of a carbon steel piece. If the material is to go through repeated cycles of magnetisation,which piece will dissipate greater heat energy?
$(c)$ '$A$ system displaying a hysteresis loop such as a ferromagnet,is a device for storing memory?' Explain the meaning of this statement.
$(d)$ What kind of ferromagnetic material is used for coating magnetic tapes in a cassette player,or for building 'memory stores' in a modern computer?
$(e)$ $A$ certain region of space is to be shielded from magnetic fields. Suggest a method.

The figure illustrates how $B$,the magnetic flux density inside a sample of unmagnetised ferromagnetic material,varies with $B_0$,the external magnetic flux density in which the sample is kept. For the sample to be suitable for making a permanent magnet: