Single-Crystal Magnetic Properties of [Co(NH₃)₅(OH₂)] [Cr(CN)₆] Between 2 and 300 K

Abstract

The magnetic susceptibilities along and perpendicular to the c axis (hexagonal setting) between 2.0 and 300 K at a magnetic field of 1.00 T, and the magnetizations at field strengths up to 5.00 T, are presented for single crystals of [Co(NH₃)₅(OH₂)] [Cr(CN)₆]. The results are interpreted in terms of zero-field splitting (2D) of the ground ⁴A_2g term by spin-orbit coupling and of magnetic exchange interaction between the chromium atoms. The magnetic exchange is modelled as one of Ising or mean-field in type. The exchange is found to be quite small: J = -0.18(6) cm^-1 if the Ising model is employed, and -0.03(1) cm^-1 for the mean-field model. The model adopted for the exchange has a strong influence on the value of the parameter D obtained. When the Ising model is used D is deduced to be -0.28(9) cm^-l; when the mean-field model is used D is -0.14(4) cm^-l. The g-values deduced are in agreement with those from e.s.r. measurements at higher temperatures and do not depend on the exchange model. In any case, D is found to be sufficiently large that it must be considered in a polarized neutron diffraction experiment on the compound.