Pseudocubic Angular Dependence of the M = −1/2 to +1/2 EPR Transitions for Ions with S = 3/2 by Small Distortions of the Cubic Crystal Field

Abstract

AbstractThe line positions of the EPR transitions — determined by the generalized spin Hamiltonian ℋ︁ = gβBS + ∫β{S Bx + S By + S Bz − 1/5 (SB) [3S(S + 1) − 1]} for cubic symmetry and S = 3/2 — are calculated to the second order of perturbation theory taking into account small rhombic distortions of the crystal field. In the case of the transition M = −1/2 ⟷ +1/2 — frequently the only one experimentally observed — it is shown that under certain conditions such distortions of the crystal field apparently cause the same cubic angular dependence as the term ∫βS3B does. Therefore, the parameters f and g determined from the experiment may contain contributions of non‐cubic fields. These contributions, which can be determined by measuring at two microwave frequencies, are calculated for four different systems of the rhombic principal axes.