Strain patterning of flexomagnetism

TL;DR

This paper introduces a top-down method to pattern transverse strain gradients in thin films, demonstrating that such gradients can induce ferromagnetism in antiferromagnetic GdAuGe, enabling precise control of magnetic phases.

Contribution

The study develops a lithography-based helium ion implantation technique to create controlled strain gradients, revealing their effect on flexomagnetism in quantum materials.

Findings

Transverse strain gradients induce ferromagnetism near room temperature.

Magnetic response correlates with regions of maximum strain gradient.

The method enables precise control of magnetic phases via patterned strain.

Abstract

Flexomagnetism, the coupling of magnetic ordering to strain gradients, provides access to novel symmetry-broken magnetic phases that cannot be accessed via uniform strain. However, flexomagnetism is hard to understand because it is extremely difficult to control a spatially varying strain. Here, we develop a top-down strategy to pattern transverse strain gradients using helium ion implantation through a lithographically defined mask. Using epitaxial films of the antiferromagnetic nodal line semimetal GdAuGe, we demonstrate that transverse strain gradients $\partial \varepsilon_{zz}/\partial x$ induce near-room-temperature ferromagnetic response, compared to the retained para or antiferromagnetism for homogeneously strained GdAuGe. We spatially correlate the magnetic response with the regions of largest strain gradient, via magnetic force microscopy and nanobeam x-ray diffraction, respectively, to confirm the flexomagnetic response. Our approach opens new avenues for the precise control of magnetic phases in thin films of quantum materials via a patterned strain gradient.