Hydrogen-driven switching of the magnetic surface anisotropy at the Co/Pd interface*

Heterostructures exhibiting perpendicular magnetic anisotropy (PMA) have proven to be indispensable within the magnetic recording industry. By exploiting the hydrogen-induced modifications to PMA which occur exclusively at the ferromagnetic/Pd interface, an opportunity exists to expand the potential applications of PMA-based heterostructures into the realm of hydrogen sensing using ferromagnetic resonance (FMR) - an electron-spin based technology. Here, we present an interface-resolved in-operando study of a Co/Pd film which features tailorable PMA in the presence of hydrogen gas. We combine polarized neutron reflectometry with in-situ FMR to explore the nanoscopic interactions of hydrogen at the Co/Pd interface which affects the spin-resonance condition during hydrogen cycling. Key experimental data and theoretical modelling reveal that the interfacial PMA of the Co/Pd film suppresses non-reversibly upon primary exposure to hydrogen gas – highlighting a potential avenue for spintronics-based hydrogen sensing.