Magnetic Susceptibility of Anisotropically Interacting Spin-Pair Systems

The Oguchi theory of antiferromagnetism has been modified for antiferromagnetically interacting spin-pair systems with anisotropic exchange interaction. The parallel and perpendicular susceptibilities $({\chi}_{\parallel}\;and\;{\chi}_{\perp})$ have been expressed as functions of exchange interactions $(J_z\;and\;{\gamma}=J_x/J_z)$, anisotropic molecular field parameters $({\kappa}\;and\;{\kappa}_x)$, $g_z\;and\;g_x$. In contrast to the previous theories, the parallel susceptibilities are not the same as the perpendicular susceptibilities above Neel temperature $T_N$.