Effect of Pressure on Tiny Antiferromagnetic Moment in the Heavy-Electron Compound URu_2Si_2

TL;DR

This study investigates how applying pressure influences the tiny antiferromagnetic moments in URu_2Si_2, revealing a phase transition and enhancement of magnetic order with increasing pressure up to 2.8 GPa.

Contribution

The paper provides new experimental data on pressure-induced changes in magnetic moments and phase transitions in URu_2Si_2 using neutron scattering.

Findings

Antiferromagnetic Bragg reflection is enhanced by pressure.

Staggered moment increases linearly with pressure below 1.1 GPa.

A phase transition occurs at around 1.5 GPa to a larger-moment antiferromagnetic phase.

Abstract

We have performed elastic neutron-scattering experiments on the heavy-electron compound URu_2Si_2 for pressure P up to 2.8 GPa. We have found that the antiferrmagnetic (100) Bragg reflection below T_m ~ 17.5 K is strongly enhanced by applying pressure. For P < 1.1 GPa, the staggered moment mu_o at 1.4 K increases linearly from ~ 0.017(3) mu_B to ~ 0.25(2) mu_B, while T_m increases slightly at a rate ~ 1 K/GPa, roughly following the transition temperature T_o determined from macroscopic anomalies. We have also observed a sharp phase transition at P_c ~ 1.5 GPa, above which a 3D-Ising type of antiferromagnetic phase (mu_o ~ 0.4 mu_B) appears with a slightly reduced lattice constant.