NEUTRON-SCATTERING STUDY OF PRESSURE-INDUCED ANTIFERROMAGNETISM IN PRSB

At low temperatures the 4f2 configuration of Pr3+ in PrSb approaches a singlet-singlet system at the X point as a result of the crystalline electric field and the anisotropy in the exchange. The energy of the longitudinal exciton decreases with applied pressure, and there is a transition at T 0°from a Van Vleck paramagnet to an induced-moment antiferromagnet at Pc=3.0±0.2 GPa. The magnetic structure, phase boundary, and magnetic moment have been determined, and they are in qualitative agreement with a molecular-field model for the transition. Near the critical pressure the longitudinal exciton softens with decreasing temperature and then saturates at a finite energy in the vicinity of the ordering temperature. RPA theories for the dynamics of the singlet-singlet model are not compatible with these results. © 1979 The American Physical Society.