Magnetic properties of Ni fine particles (0.7 μm in diameter) coated with Pd (5-30 nm thick) were studied before and after hydrogenation. The system offers the possibility of studying hydrogenation under isovolumetric constraint, but this seems to produce little change in the saturation loading. The Pd shell appears to turn weakly ferromagnetic below about 20 K under high magnetic fields, but this magnetic polarization is suppressed by hydrogenation. The lowering of the magnetization of Ni by Pd coating may be related to a change in the surface anisotropy of Ni.
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