Question

Assertion: The susceptibility of diamagnetic materials does not depend upon temperature.
Reason: Every atom of a diamagnetic material is not a complete magnet in itself.
A. Both Assertion and Reason are correct and Reason is the correct explanation for Assertion.
B. Both Assertion and Reason are correct but Reason is not the correct explanation for Assertion.
C. Assertion is correct but Reason is incorrect.
D. Both Assertion and Reason are incorrect.

Answer 1

The curie’s law is only applicable to ferromagnetic and paramagnetic materials but not for diamagnetic materials.As every atom in a diamagnetic material is not a complete magnetic in itself, the susceptibility of diamagnetic materials does not depend upon temperature.

Complete answer:
Diamagnetism is non-cooperative behaviour of orbiting electrons when exposed to an applied magnetic field. Diamagnetic substances are composed of atoms which have no net magnetic moment (i.e., all the orbital shells are filled and there are no unpaired electrons). When exposed to a field, a negative magnetization is produced and thus the susceptibility is negative.

According to curie’s law which is only applicable to ferromagnetic and paramagnetic materials susceptibility,
$\chi = \dfrac{c}{T}$
where $T$ is absolute temperature.
So the assertion is true because curie’s law is not applicable to diamagnetic waves.Magnetic susceptibility is the dimensionless proportionality constant that indicates degree of magnetisation of material in response to external magnetic field.As every atom in a diamagnetic material is not a complete magnetic in itself, the susceptibility of diamagnetic materials does not depend upon temperature.

Therefore the correct answer is option D.

Additional information: Magnetic susceptibility, quantitative measure of the extent to which a material may be magnetized in relation to a given applied magnetic field. The magnetic susceptibility of a material, commonly symbolized by χm, is equal to the ratio of the magnetization M within the material to the applied magnetic field strength H, or $χ_m$ = M/H. This ratio, strictly speaking, is the volume susceptibility, because magnetization essentially involves a certain measure of magnetism (dipole moment) per unit volume.

Magnetic materials may be classified as diamagnetic, paramagnetic, or ferromagnetic on the basis of their susceptibilities. Diamagnetic materials, such as bismuth, when placed in an external magnetic field, partly expel the external field from within themselves and, if shaped like a rod, line up at right angles to a nonuniform magnetic field. Diamagnetic materials are characterized by constant, small negative susceptibilities, only slightly affected by changes in temperature.

Note: The magnetic Susceptibility of a diamagnetic substance is negative and very slightly less than one and of the order of 10−5. There is no appreciable variation of diamagnetism with temperature that is susceptible and independent of temperature.