Magnetic order in 2D antiferromagnets revealed by spontaneous anisotropic magnetostriction

TL;DR

This study demonstrates a novel nanomechanical method to probe the temperature-dependent magnetic order parameter in 2D antiferromagnets, revealing microscopic origins and critical exponents, especially useful for insulating compounds.

Contribution

It introduces a new approach using anisotropic magnetostriction and resonance frequency measurements to analyze magnetic order in 2D antiferromagnets, supported by density functional calculations.

Findings

Resonance frequency anisotropy correlates with magnetic order parameter.

Microscopic origin of anisotropic strain confirmed by density functional calculations.

Critical exponents of magnetic order deduced from temperature and thickness dependence.

Abstract

The temperature dependent order parameter provides important information on the nature of magnetism. Using traditional methods to study this parameter in two-dimensional (2D) magnets remains difficult, however, particularly for insulating antiferromagnetic (AF) compounds. Here, we show that its temperature dependence in AF MPS$_{3}$ (M(II) = Fe, Co, Ni) can be probed via the anisotropy in the resonance frequency of rectangular membranes, mediated by a combination of anisotropic magnetostriction and spontaneous staggered magnetization. Density functional calculations followed by a derived orbital-resolved magnetic exchange analysis confirm and unravel the microscopic origin of this magnetization inducing anistropic strain. We further show that the temperature and thickness dependent order parameter allows to deduce the material's critical exponents characterising magnetic order. Nanomechanical sensing of magnetic order thus provides a future platform to investigate 2D magnetism down to the single-layer limit.