Exploiting symmetry-mismatch to control magnetism in a ferroelastic heterostructure

TL;DR

This study uses polarized neutron reflectometry to reveal how symmetry mismatch at interfaces induces structural distortions that control ferromagnetism in strained LaCoO3 thin films, providing insights into strain-induced magnetic phenomena.

Contribution

It demonstrates how interface symmetry mismatch and ferroelasticity influence magnetism in LaCoO3 heterostructures, a novel insight into strain-controlled magnetic properties.

Findings

Interfacial regions show reduced magnetization and increased atomic density.

Interior regions exhibit increased magnetization and decreased atomic density.

Hydrostatic pressure modulates the structural distortion and magnetic profile.

Abstract

In the bulk, LaCoO3 (LCO) is a paramagnet, yet in tensile strained thin films at low temperature ferromagnetism (FM) is observed, and its origin remains unresolved. Polarized neutron reflectometry (PNR) is a powerful tool to determine the depth profiles of the structure and magnetization simultaneously and thus the evolution of the interfacial FM with strain can be accurately revealed. Here we quantitatively measured the distribution of atomic density and magnetization in LCO films by PNR and found that the LCO layers near the heterointerfaces exhibit a reduced magnetization but an enhanced atomic density, whereas the interior shows the opposite trend. We attribute the nonuniformity to the symmetry mismatch at the interface, which induces a structural distortion related to the ferroelasticity of LCO. This assertion is tested by systematic application of hydrostatic pressure during the PNR experiments. These results provide unique insights into mechanisms driving FM in strained LCO films while offering a tantalizing observation that tunable deformation of the CoO6 octahedra in combination with the ferroelastic order parameter.