Magnetic circular and linear dichroism of cubic or tetragonally distorted high spin d5systems

Abstract

The low temperature, single crystal and polymer matrix absorption, magnetic circular dichroism (MCD) and magnetic linear dichroism (MLD) of the d-d electronic transitions in the tetrahalomanganates (II), [(C2H5)4N]2MnX4 (where X = Cl, Br and I), have been investigated. The effect of crystal rotation about the incident radiation propagation direction is theoretically examined and shown to yield anisotropic MLD terms for 4 T 1 and 4 E states and isotropic ones for 4 A 2 and 4 T 2 states. The combination of the sign of the MCD zeroth order moment and the MLD crystal rotational dependence is used to assign the observed bands with a high degree of certainty. It is shown that although conventional crystal field theory correctly predicts the d-d state ordering in the lowest energy range (4 T 1 < 4 T 2 < 4 E) it fails badly in the higher energy region (4 T 1 < 4 T 2 < 4 A 2). An improved model including both charge-transfer and d electron configurations is proposed to explain the discrepancy. Spin-orbit and tetra...