Question

Nickel shows ferromagnetic property at room temperature. If the temperature is increased beyond Curie temperature, then it will show
A) Diamagnetism
B) Paramagnetism
C) Anti ferromagnetism
D) No magnetic property

Answer 1

Hint : The magnetic property of any material arises from the alignment of individual magnetic moments inside the magnet. The Curie temperature is defined as the temperature where the thermal energy of the atoms will overcome the potential energy associated with the alignment of the magnetic moment of the magnet.

Complete step by step answer
Inside a magnet, there are individual magnetic moments associated with the atoms of the material of the magnet that arises due to the spin of electrons and their interaction with each other. Different types of magnetic materials are defined based on the interaction of their own magnetic moments with external magnetic fields.
For a ferromagnetic material, the individual magnetic moments are mostly aligned with each other very strongly and as a result, they have a magnetic field of their own which is permanent. The alignment of these magnetic moments is opposed by the thermal energy associated with the temperature of the surroundings of the magnet. This is because thermal energy tries to misalign the magnetic moments by providing energy for the individual magnetic moments.
Even though ferromagnetic materials have very high net magnetic moments, at one temperature, the thermal energy will overcome the alignment’s potential energy and misalign the individual magnetic moments. This temperature is known as the Curie temperature.
Above this temperature, the magnetic moments misalign and most of them cancel each other out leaving a negligible net magnetic moment that is associated with paramagnetism.
Hence option (B) is the correct choice.

Note
Urie temperature is a cut-off for the change in the magnetic property of magnets however for ferromagnetic materials, the net magnetic field drops slowly with temperature below the Curie temperature. However it is still significantly high that we can call it a ferromagnetic material. However, at temperatures greater than the Curie temperature, it will experience a significant drop in its magnetic strength.