Abstract
High magnetic field, low-temperature Zeeman measurements of the 4A2g to 4T2g zero-phonon liners of Mn4+ in Cs2SiF6 are reported. The separation of the spin-orbit components of the 4T2g term are established and are found to be an order of magnitude smaller than that predicted by static crystal-field theory. The reduction is explained in terms of Ham quenching of the off-diagonal spin-orbit interaction arising from a strong Jahn-Teller effect. Zeeman polarisations are found to be fully consistent with this Jahn-Teller model. Difficulties are, however, encountered in giving a satisfactory account of the relative intensity of the zero-phonon transitions.