Magnetic field dependence of relaxation rates of non-Kramers doublets

It was recently shown by one of the authors (MBW) that the second-order Raman process gives rise to an electron spin–lattice relaxation rate for non-Kramers ions varying as T5 at low temperatures. We determine here the magnetic field dependence of this relaxation process for a non-Kramers doublet. We find that, in contrast to the other Raman relaxation rates, the T5 rate has a frequency dependence [Formula: see text] where ω is the resonance frequency and Δ the zero-field splitting of the doublet. The magnetic field dependences of the various relaxation rates are shown to be consequences of the time-reversal symmetry properties of the non-Kramers doublet.