Which type of magnetic material has a large positive magnetic susceptibility and can remain magnetized when removed from a magnetic field?

• A. Diamagnetic
• B. Paramagnetic
• C. Ferromagnetic
• D. Superparamagnetic

Answer: (C)

The correct choice is ferromagnetic materials, which are characterized by a large positive magnetic susceptibility. These materials not only respond strongly to an external magnetic field but also have the capacity to retain their magnetization even after the external field is removed. This retention of magnetization is due to the presence of magnetic domains within the material that align in the direction of the external magnetic field and remain aligned once the field is removed, leading to permanent magnetism.

Conversely, diamagnetic materials show a weak, negative susceptibility and do not retain magnetization; they are repelled by magnetic fields. Paramagnetic materials also have a positive susceptibility but do not exhibit permanent magnetism, as their magnetic alignment requires the presence of an external magnetic field and dissipates once the field is removed. Superparamagnetic materials act similarly to paramagnetic ones at room temperature but can exhibit strong magnetization under specific conditions, such as very fine particle size. However, they also do not retain magnetization in the absence of a magnetic field like ferromagnetic materials do.