Question

Susceptibility is small and positive for
(A) Paramagnetic only
(B) Diamagnetic only
(C) Ferromagnetic only
(D) Both 1 & 3

Answer 1

Hint: Magnetic susceptibility is a measure of the degree of magnetization of material when placed in an external magnetic field. It is a ratio of magnetization (M) to the applied Magnetic field strength (H). So the $Susceptibility(\chi ) = \dfrac{M}{H}$ .

Complete step by step answer:
For a paramagnetic material, magnetic susceptibility is greater than 0 and less than 1.
$ \Rightarrow 0 < \chi < 1$
Hence for paramagnetic material, magnetic susceptibility is always positive. Some of the examples of paramagnetic material are aluminum, titanium, etc.
For diamagnetic material, magnetic susceptibility is less than or equal to 0 hence for diamagnetic susceptibility either be zero or less than one.
$ \Rightarrow \chi \leqslant 0$
Some examples of diamagnetic material are gold, silver, etc.
While for ferromagnetic material magnetic susceptibility is always positive and greater than 1.
$ \Rightarrow \chi > 1$
Some examples of ferromagnetic material are iron, nickel, cobalt, etc.

Hence the correct answer is an option (A).

Additional information: There is another type of material other than above paramagnetic diamagnetic and ferromagnetic materials, which are known as antiferromagnetic and ferrimagnetic materials. The magnetic susceptibility of such materials is temperature-dependent. The susceptibility may increase or decrease by the change in temperature of materials. The common examples of antiferromagnetic materials are chromium, and alloys like nickel oxide, and examples of ferromagnetic materials are iron garnet, etc. Also, the SI unit of magnetic susceptibility is $\dfrac{{{m^3}}}{{kg}}$ in MKS while $\dfrac{{c{m^3}}}{g}$ in the CGS system.

Note: Magnetic susceptibility should not be confused with magnetic permeability which is the parameter that expresses the total magnetization and volume of materials while Magnetic permeability is the ratio of magnetization to the magnetic field intensity.