Long range antiferromagnetic order in a rocksalt high entropy oxide

TL;DR

This study uncovers long-range antiferromagnetic order in a high entropy oxide with extreme chemical disorder, using neutron scattering techniques to reveal its magnetic structure and excitations.

Contribution

First demonstration of magnetic structure in a high entropy oxide showing long-range antiferromagnetic order despite chemical disorder.

Findings

Long-range antiferromagnetic order confirmed by neutron diffraction.

Magnetic excitations observed at room temperature.

Magnetic structure consists of ferromagnetic sheets with antiparallel spins.

Abstract

We report for the first time the magnetic structure of the high entropy oxide $(Mg_{0.2}Co_{0.2}Ni_{0.2}Cu_{0.2}Zn_{0.2})O$ using neutron powder diffraction. This material exhibits a sluggish magnetic transition but possesses a long-range ordered antiferromagnetic ground state, as revealed by DC and AC magnetic susceptibility, elastic and inelastic neutron scattering measurements. The magnetic propagation wavevector is k=(1/2, 1/2, 1/2) based on the cubic structure Fm-3m, and the magnetic structure consists of ferromagnetic sheets in the (111) planes with spins antiparallel between two neighboring planes. Inelastic neutron scattering reveals strong magnetic excitations at 100 K that survive up to room temperature. This work demonstrates that entropy-stabilized oxides represent a unique platform to study long range magnetic order with extreme chemical disorder.