MAGNETIC-ORDERING PHENOMENA IN TMS

Neutron diffraction data have been obtained from powder and single crystal specimens of TmS at temperatures ranging from room temperature to 1.7 K and in applied magnetic fields up to 42.8 kOe. In zero field TmS undergoes a transition, at about 8.9 K, to an antiferromagnetic structure which is almost the type two face-centered cubic structure. In this structure there are four G-type or (π,π,π) type antiferromagnetic sublattices such that the moments are parallel in (111) planes, alternating in sign from one such plane to the next. Superimposed on the ordering is a sinusoidal modulation with propagation vectors parallel to [110] directions. The structure is a multidomain one which gives rise to a very complex diffraction pattern. With polarization analysis it was possible to determine the moment directions in the domains. For example, in domains with propagation vector parallel to [11̄0] the moments are parallel to [112̄]. From powder data taken at 1.7 K the maximum value of the Tm moment was estimated to be 4.0 μB. Diffuse streaks of magnetic origin with temperature and field dependence different from that of the satellites were observed which may influence our estimate of the magnitude of the ordered moment. The response of the magnetic reflections to applied magnetic fields can be understood, in part, in terms of domain repopulation.