Magnetic and transport anomalies in the compounds, RCuAs₂ (R=Pr, Nd, Sm, Gd, Tb, Dy, Ho, and Er)

Abstract

The results of DC magnetization, heat capacity, electrical resistivity (ρ) and magnetoresistance measurements are reported in detail for the compounds, RCuAs₂ for R=Pr, Nd, Sm, Gd, Tb, Dy, Ho, and Er, crystallizing in HfCuSi₂-type tetragonal structure, with the aim of bringing out anomalies among 'normal' (that is, other than Ce and Yb) rare-earths. The results establish that all these compounds order antiferromagnetically at low temperatures with deviations from de Gennes scaling. Isothermal magnetization (M) data below respective Néel temperatures (T_N) reveal the existence of field-induced metamagnetic-like transitions for most of the compounds (except R=Sm and Gd), whereas in Sm and Gd compounds M varies essentially linearly with magnetic field. With respect to the ρ behavior, there appears to be a subtle difference in the temperature dependence beyond 50 K between Sm on the one hand and the rest on the other. In addition, the unexpected ρ(T) minimum reported recently for R=Sm, Gd, Tb and Dy in the paramagnetic state (around 20-30 K) is essentially absent for R=Ho and Er. The results overall reveal that the normal rare-earths in this series present an interesting situation in magnetism, warranting a new theoretical approach to describe the transport behavior in the paramagnetic state particularly in the vicinity of T_N.