Flexomagnetism and vertically graded Neel temperature of antiferromagnetic Cr2O3 thin films

P Makushko and T Kosub and OV Pylypovskyi and N Hedrich and J Li and A Pashkin and S Avdoshenko and R Hubner and F Ganss and D Wolf and A Lubk and MO Liedke and M Butterling and A Wagner and K Wagner and BJ Shields and P Lehmann and I Veremchuk and J Fassbender and P Maletinsky and D Makarov, NATURE COMMUNICATIONS, 13, 6745 (2022).

DOI: 10.1038/s41467-022-34233-5

Flexomagnetism refers to the modification of the magnetic properties of a material due to inhomogeneous strain, and offers a promising pathway to the control and manipulation of magnetism. Here, Makushko et al. explore flexomagnetism in antiferromagnetic thin films of Cr2O3, demonstrating a gradient of the Neel temperature as a result of an inhomogeneous strain. Antiferromagnetic insulators are a prospective materials platform for magnonics, spin superfluidity, THz spintronics, and non-volatile data storage. A magnetomechanical coupling in antiferromagnets offers vast advantages in the control and manipulation of the primary order parameter yet remains largely unexplored. Here, we discover a new member in the family of flexoeffects in thin films of Cr2O3. We demonstrate that a gradient of mechanical strain can impact the magnetic phase transition resulting in the distribution of the Neel temperature along the thickness of a 50-nm-thick film. The inhomogeneous reduction of the antiferromagnetic order parameter induces a flexomagnetic coefficient of about 15 mu(B) nm(-2). The antiferromagnetic ordering in the inhomogeneously strained films can persist up to 100 degrees C, rendering Cr2O3 relevant for industrial electronics applications. Strain gradient in Cr2O3 thin films enables fundamental research on magnetomechanics and thermodynamics of antiferromagnetic solitons, spin waves and artificial spin ice systems in magnetic materials with continuously graded parameters.

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