Neutron Scattering Study on Commensurate and Incommensurate Antiferromagnetic Phases in UPd2Si2 under Uniaxial Stress

TL;DR

This study uses neutron scattering to explore how uniaxial stress influences the competition between commensurate and incommensurate antiferromagnetic phases in UPd2Si2, revealing stress-induced stabilization of the commensurate phase.

Contribution

It demonstrates that uniaxial stress along [010] direction stabilizes the C-AF phase and alters magnetic transition temperatures in UPd2Si2, similar to effects seen with hydrostatic pressure.

Findings

Uniaxial stress reduces incommensurate AF order.

Transition temperature from IC to C increases under stress.

C-AF magnetic moment remains constant up to 0.8 GPa.

Abstract

The nature of competition between incommensurate (IC) and commensurate (C) antiferromagnetic (AF) orders in UPd2Si2 was investigated by performing elastic neutron scattering experiments under uniaxial stress sigma. It is found that applying sigma along tetragonal [010] direction reduces the IC-AF order, and then stabilizes the C-AF order. The transition temperature from IC- to C-AF phases T_Nl is enhanced from 109 K (sigma=0) to 112.5 K (0.8 GPa), while the onset of IC-AF transition T_Nh is unchanged from 132 K under sigma. In addition, c-axis component q_z of the IC-AF modulation at 115 K also increases from 0.736 (sigma=0) to 0.747 (0.8 GPa). The magnitude of C-AF moment at 5 K is estimated to be 2.2 mu_B/U in the entire sigma range presently investigated (sigma <= 0.8 GPa). These features are similar to those obtained from the investigations using hydrostatic pressure p, indicating that applications of p and sigma||[010] commonly induce the crystal strains which inherently affect a delicate balance of frustrated magnetic interactions between uranium 5f moments.