Preparation and magnetic properties of amorphous and nanocrystalline Sm2Co17 alloys

The single-phase Sm2Co17 alloys with amorphous and nanocrystalline structures were prepared separately by a simplified route combining high-energy ball milling and spark plasma sintering. The microstructure evolution, as well as the phase transformation, were investigated for the prepared Sm2Co17 alloys. It was found that the nanocrystalline Sm2Co17 alloy has a stable hexagonal crystal structure at the room temperature, which shows different phase stability from the conventional polycrystalline Sm2Co17 alloys. In contrast with the coarse-grained Sm2Co17 ingot that shows very weak permanent magnetic properties, the amorphous and nanocrystalline Sm2Co17 alloys exhibit apparently improved magnetic properties. The first-principles calculations show that a much higher spin polarization is achieved in the nanocrystalline Sm2Co17, as compared with the coarse-grained polycrystalline counterpart. Due to the intense spin polarization at the Fermi level, the exchange interaction between Sm(4f) and Co(3d) electrons is enhanced, which results in the strong magnetism in the nanocrystalline Sm2Co17 alloy.