Magnetic properties and Pd-H miscibility gap in Ni/Pd composite fine particles

The magnetic and structural properties of Ni fine particles coated with Pd were investigated in hydrogen atmospheres by means of in situ magnetometry and in situ x-ray diffractometry. The x-ray diffraction patterns in hydrogen atmospheres show that the width of the plateau in the Pd-H phase boundary (miscibility gap) narrows with decreasing Pd thickness, which is reminiscent of nano-crystalline Pd. At room temperature, the magnetization in hydrogen atmospheres shows a steep saturation and a small decrease in the residual magnetization, indicating that the interface magnetic anisotropy is reduced by the hydrogenation.