Antiferromagnetic Resonance in CoCl₂6H₂O

Abstract

Antiferromagnetic resonance experiment was performed on a single crystal of CoCl 2 6H 2 O in the frequency range of 9.5 to 47 kMc/sec at liquid helium temperature. The result can be understood by the theory of antiferromagnetic resonance developed by Nagamiya and Yosida and also by Ubbink et al., except for certain systematic deviations from the theory. These deviations can be removed by introducing a large anisotropic exchange interaction of the symmetric tensor form in place of the ordinary small anisotropy energy. Thus, the effective fields acting on sublattice magnetizations, M + and M - , are assumed to be of the form \begin{aligned} {H_{E}}^{\pm}{=}-AM^{\mp}-\varGamma M^{\pm}-A'M^{\mp}-\varGamma'M^{\pm}, \end{aligned} where A and \(\varGamma\) are the isotropic molecular field constants and A ' and \(\varGamma'\) are newly introduced anisotropic molecular field tensors. It was found that the symmetry axes of A ' and \(\varGamma'\) coincide with those of the g -tensor and their components are given by