Magnetic Properties of Solid Solution Co_xNi_1-xCl₂6H₂O

Abstract

The magnetic properties and the phase diagram of the solid solution Co x Ni 1- x Cl 2 6H 2 O are analyzed by using a model Hamiltonian with the mean field approximation. Our results are qualitatively in agreement with experimental ones. It is shown that the sublattice magnetization lies in a plane including both easy axes of two pure substances ( ca -plane) and its direction varies smoothly over the whole range of the concentration x , not within a limited range of x as observed in K 2 Mn x Fe 1- x F 4 and Co x Fe 1- x Cl 2 2H 2 O. The feature is due to off diagonal terms in the Hamiltonian which come from the non-orthogonality of the easy axes of two pure substances CoCl 2 6H 2 O and NiCl 2 6H 2 O (∼65°). The characteristic features of the magnetization processes are also analyzed considering the fact that the second easy axis of CoCl 2 6H 2 O does not lie within the ca -plane.