Magnetic Properties of RXO₄ System

Abstract

The magnetizations of phosphates and vanadates of rare-earth elements RXO₄ (R=Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er and Yb, and X=P and V) were studied in the temperature range of 1.9°K to 630°K. There were not found any magnetic transitions between 4.2°K and 630°K for all system, while F. F. Y. Wang et al. reported some antiferromagnetic transitions for GdPO₄, TbPO₄ (zircon structure) and DyPO₄ at 225°K, 415°K and 505°K, respectively. Below 4.2°K, TbPO₄ (zircon structure) and DyVO₄ showed the metamagnetic-like behaviours and seemed to have antiferromagnetic transition points between 1.9°K and 4.2°K. Above 200°K, the magnetizations of all materials followed the Curie-Weiss law. The slope of inverse susceptibility vs temperature plots suggest that the magnetic moments localized on these materials come from those of trivalent cations R³⁺. The nuclear magnetic resonances (NMR) of P³¹ and V⁵¹ in these materials were measured at room temperature. The NMR shifts of P³¹ were very small (−0.015%∼+0.038%) and any resonances were not observed for DyPO₄, HoPO₄ and ErPO₄. As for the V⁵¹ NMR, no resonances were observed except for the NdVO₄, which was also small (−0.053%). No arguments were made for SmPO₄ and EuPO₄ because of their extremely small susceptibilities.