Multi-axis cavity optomechanical torque characterization of magnetic microstructures and the contribution of the Einstein-de Haas effect

Significant new functionality is reported for torsion mechanical tools aimed at full magnetic characterizations of both spin statics and dynamics in micro- and nanostructures. Specifically, multiple torque directions utilizing higher order mechanical modes are monitored, as is essential for study of anisotropic three-dimensional structures. The approach is demonstrated through application to shape and microstructural disorder-induced magnetic anisotropies in lithographically patterned permalloy, and will have utility for the determination of important magnetic thin-film and multilayer properties including interface anisotropy and exchange bias.

With the extension of torque magnetometry measurements into radio frequencies, the contribution of the Einstein-de Haas (EdH) effect can become comparable to the conventional magnetic cross-product signal. Through sensitive optomechanical detection of higher order mechanical modes, the torques owing to the EdH effect are elucidated, and offer a new method for exploring high frequency magnetic susceptibility in anisotropic structures.