Thermally modulated hydrogenation in FexPd1−x alloy films: Temperature-driven peculiar variation of magnetism

The sensitive hydrogen effect on spintronic materials has been recently demonstrated to have high application potential. However, the correlation between hydrogen pressure (PH2), temperature, and magnetic properties still remains unclear. In this study, the magnetic moment of Fe in an Fe–Pd alloy thin film was increased through hydrogen absorption, as evidenced by the enhanced x-ray magnetic circular dichroism signal of Fe. Hydrogen absorption and desorption hysteresis loops in the magnetic coercivity Hc-PH2 diagram revealed that most hydrogen was absorbed when PH2 was above 10 mbar and desorbed when PH2 was approximately 10–6 mbar. The hydrogenation effect on the magnetism of an Fe–Pd alloy film was eliminated at an annealing temperature of 360 K without considerable hydrogen desorption. The annealing-driven cyclic enhancement of Hc was demonstrated because of the competition between thermal activation and H bonding. These results clearly reveal the critical temperature dependence and provide applicable knowledge of the hydrogenation effect on magnetic Pd-alloys.