Explain the behavior of a superconductor as a diamagnetic material.

(N/A) Superconductors are a special class of materials that exhibit perfect diamagnetism. When a material is cooled below its critical temperature $(T_c)$, it transitions into a superconducting state.
In this state, the superconductor expels all magnetic field lines from its interior, a phenomenon known as the $Meissner$ effect. Because the magnetic field inside the superconductor is zero $(B = 0)$, it behaves as a perfect diamagnet.
For a perfect diamagnet, the magnetic susceptibility $(\chi)$ is $-1$. Since the relative permeability is given by $\mu_r = 1 + \chi$, we get $\mu_r = 1 + (-1) = 0$.
Due to this property, superconductors are strongly repelled by external magnetic fields. This effect is utilized in advanced technologies, such as magnetic levitation in high-speed maglev trains.