(N/A) Magnetic susceptibility $\chi$ is defined as the ratio of the intensity of magnetization $M$ to the magnetic intensity $H$, i.e., $\chi = M/H$.
$(i)$ For paramagnetic materials, the atoms have a permanent magnetic dipole moment. When placed in an external magnetic field, they get weakly magnetized in the direction of the field. Thus, the magnetic susceptibility $\chi$ is small and positive ($0 < \chi < \epsilon$, where $\epsilon$ is a small positive number).
$(ii)$ For diamagnetic materials, the atoms develop an induced magnetic dipole moment in a direction opposite to the applied magnetic field. Thus, they are weakly repelled by the field. The magnetic susceptibility $\chi$ is small and negative ($-1 \le \chi < 0$).