Radiofrequency studies of TmVO 4

Abstract

The electronic ground state of Tm 3+ , 3 H 6 , is a non-Kramers doublet which, below a critical temperature T D , is split by a cooperative Jahn-Teller distortion. Radiofrequency measurements of the susceptibility have established that ( a ) T D = 2.156(5) K; ( b ) most of the magnetic specific heat above T D comes from random splittings of the doublet, ascribed to local strains; (c) the critical field B c needed to counteract the distortion below T D follows very closely the molecular field theory for spin ½. Measurements of the 51 V n.m.r. spectrum above T D give values for the internal field at both V and Tm sites; interactions between Tm ions are predominantly dipolar. Below T D , both the 51 V spectrum and the enhanced 169 Tm spectrum show anisotropy in the (001) plane, whose principal axes, [110] and [110], confirm that these are the principal axes of the Jahn-Teller distortion. The temperature at which the enhanced 169 Tm nuclear moments should enter an ordered phase is estimated as 0.2-0.3mK.