Magnetic behaviour of R2PdSi3 compounds with R = Ce, Nd, Tb-Er

The magnetic behaviour of the ternary intermetallics, R2PdSi3 (R = Ce, Nd, Tb-Er), has been investigated by magnetisation, electrical-resistivity (rho) and neutron-diffraction measurements. The neutron-diffraction data reveal that these compounds crystallise in the AlB2-type hexagonal structure and that these alloys exhibit different magnetic structures below respective magnetic-transition temperatures. In Ce2PdSi3 the Ce moments order below 2.5 K in a sinusoidally modulated antiferromagnetic structure, without extending to the entire crystal, apparently exhibiting cluster magnetism. The Nd magnetic moments in Nd2PdSi3 exhibit ferromagnetic ordering below 17 K. In Tb2PdSi3, a complex situation is observed: in the temperature range from 1.5 to (T-N =)25 K, there is a coexistence of a ferromagnetic spiral (about 75% of the magnetic moment) and a spin-glass (about 25%). For the Dy, Ho and Er compounds, below T-N (7.5, 8 and 7 K, respectively), sinusoidaly modulated structures are observed and below T-N, there are upturns in rho, indicative of the opening up of magnetic Brillouin-zone-boundary gaps in these compounds. While for the Ce compound the magnetic moment lies in the basal plane, for other compounds it is parallel to the c-axis. (C) 1999 Elsevier Science B.V. All rights reserved.