Nickel shows the ferromagnetic property at room temperature. If the temperature is increased beyond Curie temperature, then it will show:
-
paramagnetism
-
anti -ferromagnetism
-
no magnetic property
-
diamagnetism
A.
paramagnetism
Nickel exhibits ferromagnetism because of a quantum physical effect called exchange couplingin which the electron spins of one atom interact with those of neighbouring atoms. The result is aligment of the magentic dipole moments of the atoms, inspite of the randomizing tendency of atomic collisions. The presistent aligment is what gives ferromagnetic material their permanent magnetism.
If the temerature of ferromagnetic material is raised above a certain critical value, called the Curie temperature, the exchange coupling ceases to be effective. Most such material then become simply tend to align with an external field but much more weakly, and thermal agitation can now more easily distrupt the alignmet.
