Hydrogen-induced magnetic and structural changes in Pd/Co/Mg multilayer

Hydrogenation-induced effects on magnetism have been widely studied because of their several potential applications. In this study, magnesium (Mg) was added to palladium (Pd)/ferromagnetic multilayers to enhance and stabilize the effects of hydrogenation. Bulk Mg is known to require high temperature and high pressure to absorb hydrogen (H). With the catalytic Pd-capping layer, Mg is confirmed to absorb H at room temperature under 1 bar H₂ pressure. The magneto-optic Kerr effect of Pd/Cobalt (Co)/Mg multilayer was measured under vacuum and under 1 bar H₂ pressure for comparison. The hydrogenation effect enhanced the magnetic coercivity from 25 to approximately 200 Oe irreversibly. Correspondingly, the surface roughness increased from 0.1 to 6 nm. The crystalline structure, as confirmed using X-ray diffraction, transformed from pure Mg to magnesium hydride (MgH₂) after hydrogenation. These observations reveal the correlation between MgH₂ formation and the magnetic properties of the Pd/Co/Mg multilayer and are valuable for the control of H-migration in spintronic devices.