In this study, the microscopic origin of the hydrogen effect on magnetic materials was explored through the characterization of time-dependent magnetic domain evolution. We prepared 25-nm Co30Pd70 alloy films with canted magnetic moment on SiO2/Si(001) substrates. From macroscopic Kerr hysteresis loops, considerable hydrogen-induced reduction of magnetic coercivity by a factor of 1/5 in a longitudinal direction and enhancement of magnetic remanence to saturation ratio from 60% to 100% were observed. The magnetic reversal behavior of the Co30Pd70 alloy films gradually transformed from nucleation-to domain-wall-motion dominance when H2 pressure was increased from a vacuum of 1 × 10-5 mbar to 0.8 bar. Domain size also increased considerably with H2 pressure. When H2 pressure was above 0.4 bar, the domain wall (DW) motion was clear to observe and the DW velocity was approximately 10-6-10-5 m/s. Greater hydrogen content in the Co30Pd70 alloy films promoted DW motion that was closer to the behavior of a thermally activated model. The hydrogen effects on magnetism were observed to be reversible and could have valuable future application in spintronic devices for hydrogen sensing.
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