Bulk nanocrystalline gadolinium metal was prepared using spark plasma sintering (SPS) and subsequent annealing process. The SPS Gd metal had a single phase with a mean grain size of about 10nm. A pressure-induced C-axis crystal texture was found in the SPS Gd sample. With the decrease of Gd grains from micrometer to nanometer range, the Curie temperature TC decreased by 10.7K and the magnetic moment per Gd atom at 5K dropped noticeably from 7.81μB to 6.31μB. These results indicate the remarkable influence of the nanostructure on the magnetism of Gd due to the finite size effect.

A series of layer structural composite magnetic refrigerant materials with composition of (Gd5Si2Ge2)x(Gd)y(Gd5Si1.85Ge2.15)z was synthesized via spark plasma sintering technique. The adiabatic temperature change (ΔTad) of the composites and of the three individual components was measured directly from 245to315K with a magnetic field change of 1.5T using a homemade magnetocaloric effect measuring apparatus. For all composites with different x:y:z ratios, their resultant ΔTad uniformly peaks at 246, 276, and 296K, respectively, corresponding to the magnetic transition temperature of the three components. In addition, proper x:y:z ratio can improve both the value and the constancy of ΔTad of the composite. Compared with the three components, the value of ΔTad of the composites exhibits a more constant tendency, which is more suitable for practical application in room temperature refrigeration, when compared to those of the three components.

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