On the magnetic anisotropy and susceptibility of Fe(NH 4 SO 4 ) 2 , 6H 2 O

Abstract

The theory of magnetic anisotropy and susceptibility of Fe²⁺ in Tutton salts has been worked out on the basis of Abragam & Pryce’s method. It is found that the anisotropic part of the crystal field changes with temperature owing to the thermal expansion of the crystal lattice. The spin-orbit coupling coefficient has to be decreased by ~ 20 % from its free ion value of - 103 cm^-1 which indicates some amount of overlap between the 3d-Fe²⁺ and 8- and p-O^2- charge clouds. The agreement of the theoretical values with the experiment is good within the limitations of the approximations involved.