Hydrogen in amorphous magnetic alloys

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Abstract
Iron-rich Y1−xFex amorphous alloys have been charged electrolytically with hydrogen to an H:Y ratio of approximately 3. The alloys are originally asperomagnetic, with spin freezing temperatures below 110 K, but they become soft ferromagnets on hydrogenation with Curie temperatures in excess of 400 K. The iron moment in a–Y12Fe88 changes from 1.96 to 2.24 μB in the hydride and the isomer shift increases by 0.15 mm/s. However, it appears that the main effect of the hydrogen is to shift a broad, mostly ferromagnetic exchange distribution with some antiferromagnetic interactions to an overwhelmingly ferromagnetic one. This is attributed to dilation of the iron–iron nearest-neighbour distances. By contrast, no significant effects on magnetic moment or exchange were detected on hydrogenating amorphous Fe40Ni38Mo4B18 (Metglas 2826 MB), but the in-plane anisotropy was modified and the soft magnetic properties degraded.