The magnetic susceptibility of material is chi = -1 and relative magn…

The correct answer is Option (3) → Diamagnetic

The magnetic susceptibility \( \chi \) tells how strongly a material is magnetised by an applied field, and it is linked to the relative permeability by

    \( \displaystyle \mu_r = 1 + \chi \)

A negative susceptibility means the material is magnetised opposite to the applied field, which is the mark of a diamagnetic material. Putting \( \chi = -1 \) gives \( \mu_r = 0 \), so the field inside is zero: the material expels the field completely. This is a perfect diamagnet, the behaviour of a superconductor.

Option (1) Paramagnetic — Incorrect. A paramagnetic material has a small positive susceptibility, so \( \mu_r \) is a little more than 1, not zero.

Option (2) Ferromagnetic — Incorrect. A ferromagnetic material has a very large positive susceptibility and \( \mu_r \) of the order of thousands.

Option (3) Diamagnetic — Correct. Negative \( \chi \) is diamagnetism, and \( \chi = -1 \) is its extreme case, perfect diamagnetism.

Option (4) Electromagnetic — Incorrect. An electromagnet is a device, a coil with a soft iron core; "electromagnetic" is not a class of magnetic material.

NCERT (2026-27):
Diamagnetism – “… The most exotic diamagnetic materials are superconductors. These are metals, cooled to very low temperatures which exhibits both perfect conductivity and perfect diamagnetism. Here the field lines are completely expelled! \( \chi = -1 \) and \( \mu_r = 0 \).”