Antiferromagnetic long-range order in $5d^1$ double-perovskite Sr$_2$MgReO$_6$

TL;DR

This study reveals that Sr$_2$MgReO$_6$, a double-perovskite with heavy transition metals, exhibits layered antiferromagnetic order below 55 K, challenging previous spin glass assumptions and highlighting its potential for exotic magnetic phenomena.

Contribution

The paper provides the first direct evidence of antiferromagnetic long-range order in Sr$_2$MgReO$_6$, clarifying its magnetic ground state and establishing it as a candidate for studying complex magnetic orders.

Findings

Sr$_2$MgReO$_6$ exhibits AF order below 55 K.

Magnetic susceptibility and heat capacity support AF order.

Contrasts previous spin glass hypothesis.

Abstract

The double-perovskite A$_2$BB'O$_6$ with heavy transition metal ions on the ordered B' sites is an important family of compounds to study the interplay between electron correlation and spin-orbit coupling (SOC). Here we prepared high-quality Sr$_2$MgReO$_6$ powder and single-crystal samples and performed non-resonant and resonant synchrotron x-ray diffraction experiments to investigate its magnetic ground state. By combining the magnetic susceptibility and heat capacity measurements, we conclude that Sr$_2$MgReO$_6$ exhibits a layered antiferromagnetic (AF) order at temperatures below $\sim$ 55 K with a propagation vector q = (001), which contrasts the previously suspected spin glass state. Our works clarify the magnetic order in Sr$_2$MgReO$_6$ and demonstrate it as a candidate system to look for magnetic octupolar orders and exotic spin dynamics.