MAGNETIC-STRUCTURES OF RNISB COMPOUNDS (R = RARE-EARTHS) INVESTIGATEDBY NEUTRON-DIFFRACTION

The magnetic structures of RNiSb compounds (R = Ce, Nd, Tb, Dy, Ho) ha ve been investigated by neutron diffraction. At low temperatures, the hexagonal compound NdNiSb shows a ferromagnetic order, whereas CeNiSb has a modulated structure with a ferromagnetic component. The cubic co mpounds Tb-, Dy-, and HoNiSb order antiferromagnetically with a propag ation vector Q = (0.5, 0.5, 0.5). In the latter semiconducting phases, negative superexchange interactions between nearest neighbours should dominate. The crystal electric field plays an important role in all c ompounds. (C) 1998 Elsevier Science B.V. All rights reserved.