Magnetic anisotropy and second-order crystal fields in some tetragonally distorted tetrahedral cobalt(II) ions

Abstract

The principal and average magnetic moments of Cs₃CoX₅ and (Et₄N)₂CoX₄, [X = Cl, Br] have been measured in the temperature range 80–300 K. Magnetic transitions showing small hysteresis effects are found for both tetraethylammonium salts. The results are correlated with a point-charge model of D_2d symmetry by use of the complete spin-quartet basis, and with previously reported zero-field-splitting parameters for the two caesium salts. Distortions are very similar in the chlorides and bromides as are effective spin–orbit coupling parameters and orbital reduction factors. The most important observation is that all spectral and magnetic properties in formal tetrahedral cobalt(II) ions are extremely insensitive to the second-order crystal-field parameter, Cp.