Flexomagnetism of thin Cr₂O₃ films

Cr₂O₃ is the only known uniaxial antiferromagnetic material that is also magnetoelectric at room temperature. This renders Cr₂O₃ a technologically relevant playground for the realisation of different device ideas for prospective antiferromagnetic spintronics. We discovered the presence of flexomagnetic effects in Cr₂O_3, which come about due to the impact of a strain gradient on the thermodynamic properties, namely on the Neel temperature. By combining magnetotransport and Nitrogen Vacancy magnetometry characterizations, we experimentally determine the presence of the gradient of the Neel temperature in a 50-nm-thick Cr₂O₃ thin film and quantify that the magnetic moment, generated by this new effect, can be as high as 15 μ_B/nm². Furthermore, due to good oxide-oxide heteroepitaxy and respective compressive strain, the Neel temperature in Cr₂O₃ thin films can be enhanced persistently up to 100 °C, which is 60 °C higher than the bulk transition temperature. The emergent flexomagnetism-driven ferromagnetic order parameter in antiferromagnetic thin films offers more flexibility in the design of spintronic and magnonic devices and can be of relevance for other antiferromagnetic materials.