Case: Read the passage and answer the question.
In terms of the susceptibility, we can classify materials as diamagnetic, paramagnetic or ferromagnetic. Diamagnetic substances are those which have a tendency to move from the stronger to the weaker part of an external magnetic field. In other words, unlike the way a magnet attracts metals like iron, it would repel a diamagnetic substance. Paramagnetic substances are those which get weakly magnetised when placed in an external magnetic field. They have a tendency to move from a region of weak magnetic field to a region of strong magnetic field, i.e., they get weakly attracted to a magnet. Ferromagnetic substances are those which get strongly magnetised when placed in an external magnetic field. They have a strong tendency to move from a region of weak magnetic field to a region of strong magnetic field, i.e., they get strongly attracted to a magnet.
A ferromagnetic sample is heated steadily to a high enough temperature. What happens to it?
Answer & explanation
Correct answer: option 2
The correct answer is Option (2) → Its domain structure breaks up and it becomes a paramagnet.
A ferromagnet is strongly magnetised because its atomic dipoles line up together over regions called domains. Heating increases the random motion of the atoms. This disturbs the line-up.
Option (1) It becomes a diamagnet. — Incorrect. The atoms of a ferromagnet have dipole moments of their own, and heating does not remove them. In a diamagnet, the resultant moment of each atom is zero.
Option (2) Its domain structure breaks up and it becomes a paramagnet. — Correct. At a high enough temperature the domains break up. The atomic dipoles no longer point together, and the sample behaves like a paramagnet.
Option (3) Its magnetisation vanishes suddenly, while its domains stay as they are. — Incorrect. The magnetisation is lost bit by bit as the domains break up. It falls gradually as the temperature rises.
Option (4) Its domains grow larger, and it stays a ferromagnet. — Incorrect. Domains grow when an external field is applied to the sample. Heating does the opposite, because it breaks up the domain structure.
NCERT (2026-27):
Ferromagnetism – “The ferromagnetic property depends on temperature. At high enough temperature, a ferromagnet becomes a paramagnet. The domain structure disintegrates with temperature. This disappearance of magnetisation with temperature is gradual.”