Optical absorption spectra of MnCl2.2H2O. II

Abstract

For pt.I see ibid., vol.10, no.20, p.4089 (1977). Absorption lines of MnCl2.2H2O corresponding to 6A1g to 4T2g(II) transition and their Zeeman effects are studied theoretically in the magnetically ordered phase under the ligand- and molecular-field approximation. All the lines are interpreted as magnon sidebands. The energy, polarisation, relative intensity and external field dependence show fair agreement with experiment. The principal axes x', y' and z of an orthorhombic field around Mn2+ in the excited state do not coincide with the crystal symmetry axes c, a', b and are rotated by pi /4 around b(z). The large and negative value of the tetragonal field around the y' axis is assumed to explain the polarisation of the lowest two Kramers doublets. To understand the small splitting of the lowest Kramers doublet (V1, V2) in H//y', a relatively large value for the magnitude of molecular field in the excited state mod mu BH'E mod has to be chosen.