Hydrogenation effect on uniaxial magnetic anisotropy of a Co_xPd_1−x alloy microstructure

In this study, Co_xPd_1−x alloy thin films and microstructures were grown through an e-beam heated co-evaporation method on Al₂ O₃(0001) substrates. The Fourier transformation analysis of high-resolution transmission electron microscopy images revealed a structural transition from a partial crystalline structure in the bottom layer region to a well-ordered crystalline structure in the top layer region. Increasing the Pd content in the Co_xPd_1−x thin films shifted the magnetic anisotropy toward the perpendicular direction. Correspondingly, magnetic force microscopy revealed submicrometer-scale magnetic domain structures for Co_xPd_1−x thin films, where x = 37%–50%. By combining oblique deposition and a grid mask, this study fabricated a 1-dimensional (1-D) microstructured Co₅₀ Pd₅₀ thin film that exhibited uniaxial magnetic anisotropy (UMA). Hydrogenation exerted a more sensitive effect on the magnetic properties of this structured thin film than it did on those of a continuous thin film. After hydrogen absorption, the magnetic coercivity was enhanced by approximately 50% and squareness by more than 100%. The reversibility of the hydrogenation effect on the UMA was also demonstrated. These observations suggest that the 1-D microstructured Co[sbnd]Pd film is sensitive and suitable for applications related to sensing hydrogen gas.