Hydrogen-mediated magnetic domain formation and domain wall motion in Co₃₀Pd₇₀ alloy films

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.