Molecular Model for the Second-Order Magnetic Field Effect on the ⁴E(G) Level of Mn²⁺ in ZnS

A covalent model is presented for the contribution of the orbital part in μ_BL · H of the Zeeman Hamiltonian to the anisotropy of the magnetic field effect on the ⁴E(G) level at lower energy of Mn²⁺ in ZnS. First, the coefficients dg_A1 and dg_E which describe the influence of μ_BL · H are given in terms of the matrix elements of a second-order perturbation scheme involving the spin–orbit (SO) interaction and the orbital operator in L · H. Second, a molecular model involving the molecular SO interaction is elaborated. It is shown that the theoretical values dg_{A1 th} = 0.025 cm^—1 and dg_{E th} = 0.040 cm^—1 as given by the covalent model are in good agreement with the experimental values dg_{A1 exp} = 0.02 cm^—1 and dg_{E exp} = 0.04 cm^—1. Third, the theoretical values given by the covalent model are compared to the values given by the crystal field (CF) model. Finally, the influence of the Jahn-Teller effect on dg_E is briefly analyzed.