Collinear antiferromagnetic order in URu2Si2−xPx revealed by neutron diffraction

M C Rahn,C Hoffmann,F Orlandi,P Manuel,R Baumbach,M Janoschek,A Gallagher,D D Khalyavin

doi:10.1103/physrevb.103.214403

Abstract

The hidden order phase in URu$_2$Si$_2$ is highly sensitive to electronic doping. A special interest in silicon-to-phosphorus substitution is due to the fact that it may allow one, in part, to isolate the effects of tuning the chemical potential from the complexity of the correlated $f$ and $d$ electronic states. We investigate the new antiferromagnetic phase that is induced in URu$_2$Si$_{2-x}$P$_x$ at $x\gtrsim0.27$. Time-of-flight neutron diffraction of a single crystal ($x=0.28$) reveals $c$-axis collinear $\mathbf{q}_\mathrm{m}=(\frac12,\frac12,\frac12)$ magnetic structure with localized magnetic moments ($\approx2.1\,\mu_\mathrm{B}$). This points to an unexpected analogy between the (Si,P) and (Ru,Rh) substitution series. Through further comparisons with other tuning studies of URu$_2$Si$_2$, we are able to delineate the mechanisms by which silicon-to-phosphorus substitution affects the system. In particular, both the localization of itinerant 5$f$ electrons as well as the choice of $\mathbf{q}_m$ appears to be consequences of the increase in chemical potential. Further, enhanced exchange interactions are induced by chemical pressure and lead to magnetic order, in which an increase in inter-layer spacing may play a special role.

Highlights

The complexity of energetically nearly degenerate electronic states in strongly correlated materials often gives rise to unusual ordering phenomena and exotic physics [1,2]
These observations are consistent with recent Nuclear magnetic resonance (NMR) measurements, which revealed a commensurate internal field Hint ≈ 0.85 kOe oriented along the c direction in the antiferromagnetic state of
Using state-of-the-art neutron time-of-flight diffractometers, we were able to determine the magnetic structure in a minute single crystal of URu2Si2−xPx (x > 0.27)

Summary

Introduction

The complexity of energetically nearly degenerate electronic states in strongly correlated materials often gives rise to unusual ordering phenomena and exotic physics [1,2]. It is challenging to identify the hierarchy of the underlying interactions between charge, orbital, magnetic, and structural degrees of freedom. Such is the case for the hidden order (HO) state that emerges in the heavy-fermion material URu2Si2. The characteristics and symmetry of the HO state itself are known to be markedly different from conventional spin or charge orders in strongly correlated metals [6].

Results

Discussion

Conclusion