Magnetic nature of wolframite MgReO$_4$

TL;DR

This study investigates the magnetic properties of MgReO$_4$, a wolframite-structured compound, revealing antiferromagnetic order below 85 K, a possible structural transition at 280 K, and a spin reorientation at 65 K using muon spin rotation and heat capacity measurements.

Contribution

First detailed magnetic investigation of MgReO$_4$ using $bc^+$SR, identifying multiple magnetic and structural transitions in this high-pressure synthesized material.

Findings

Antiferromagnetic order below 85 K.

Subtle transition at 280 K likely structural.

Spin reorientation at 65 K from collinear to canted AF.

Abstract

Rhenium oxides belonging to the family $A$ReO$_4$ where $A$ is a metal cation, exhibit interesting electronic and magnetic properties. In this study we have utilized the muon spin rotation/relaxation ($\mu^+$SR) technique to study the magnetic properties of the MgReO$_4$ compound. To the best of our knowledge, this is the first investigation reported on this interesting material, that is stabilized in a wolframite crystal structure using a special high-pressure synthesis technique. Bulk magnetic studies show the onset of an antiferromagnetic (AF) long range order, or a possible singlet spin state at $T_{\rm C1}\approx90$~K, with a subtle second high-temperature transition at $T_{\rm C2}\approx280$~K. Both transitions are also confirmed by heat capacity ($C_p$) measurements. From our $\mu^+$SR measurements, it is clear that the sample enters an AF order below $T_{\rm C1}=T_{\rm N}\approx85$~K. We find no evidence of magnetic signal above $T_{\rm N}$, which indicates that $T_{\rm C2}$ is likely linked to a structural transition. Further, via sensitive zero field (ZF) $\mu^+$SR measurements we find evidence of a spin reorientation at $T_{\rm Cant}\approx65$~K. This points towards a transition from a collinear AF into a canted AF order at low temperature, which is proposed to be driven by competing magnetic interactions.