Thermal stability and aging effect of hydrogen-implanted bubble garnet films

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Abstract
Aging and thermal stability have been studied for a hydrogen-implanted bubble garnet by measuring the effective anisotropy field change Δ(Hk−4πMs) and the lattice strain (Δa⊥/a) in the normal direction to the film. After annealing, a large decrease of Δ(Hk−4πMs) has been observed due to the out-diffusion of hydrogen. It has been found that a larger Δ(Hk−4πMs) is kept after annealing in samples with SiO2 deposited on the garnet surface. The relaxation process of (Δa⊥/a) corresponding to Δ(Hk−4πMs) shows two activation energies EA (0.8 eV and 1.6 eV) for H+2 -implanted samples. A fast relaxation process (EA =0.8 eV) is peculiar to the H+2 -implanted samples due to the out-diffusion of hydrogen and has not been observed for He+ or Ne+ implanted samples. From the aging test, it has been established that the lifetime t is about 5000 years to assure 99% stability of Δ(Hk−4πMs) at 100 °C for samples stabilized at 400 °C after SiO2 deposition.