Enhancement of the hidden order/large moment antiferromagnetic transition temperature in the URu2−xOsxSi2 system

Abstract

Electrical resistivity, specific heat, and magnetization measurements on the URuOsSi system suggest a phase transition from the ‘hidden order’ phase to another unidentified phase that is likely to be a large moment antiferromagnetic phase. It is noteworthy that the hidden order/large moment antiferromagnetic phase boundary is enhanced from 17.5 K at = 0 to 50 K at = 1. However, as increases, the gap opening in the Fermi surface due to the hidden order phase transition, deduced from electrical resistivity and specific heat measurements, decreases. This study reveals that both Fe and Os isoelectronic substitutions for Ru in URuSi yield an enhancement of . In contrast to the URuFeSi system, where the unit cell volume decreases with , in the URuOsSi system, the unit cell volume increases with . Thus the enhancement of the hidden order/large moment antiferromagnetic transition temperature cannot be solely due to an increase in chemical pressure.