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

Abstract

The magnetic behaviour of the ternary intermetallics, R₂PdSi₃ (R=Ce, Nd, Tb-Er), has been investigated by magnetisation, electrical-resistivity (ρ) 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 ρ, 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.