Towards Freestanding Cr₂O₃ Membranes

Understanding the role of strain in shaping antiferromagnetic order unlocks new insights into quantum materials. With antiferromagnetic insulators like Cr₂O₃ emerging as platforms for high-frequency, energy-efficient technologies, exploring innovative strain techniques becomes increasingly relevant. However, systematic manipulation of the strain state of Cr₂O₃ films is challenging due to limitations in on-substrate strain relaxation. In this work, we optimize fabrication of freestanding Cr₂O₃ membranes—a form not previously realized—by depositing thin films via pulsed laser deposition (PLD) onto a sacrificial layer, which is later removed through wet etching. This approach results in flexible membranes that can be mechanically manipulated in novel ways, enabling precise control over the strain state. Draping these membranes over SiN substrates with micron-scale holes induces mechanical buckling, generating second order strain effects. We also create mechanically supported strained states, such as periodic bending, to further explore the effect of strain gradients. Using the spin Hall effect (SHE) in Pt sensing layers, we investigate the room-temperature magnetic transition in Cr₂O₃ in membrane and epitaxial film form. These freestanding membranes provide a versatile platform to study the effects of strain on magnetic properties in novel geometries, opening avenues for exploring Dzyaloshinskii–Moriya interactions (DMI) and second-order strain-magnetism coupling.