Abnormal crystal structure stability of nanocrystalline Sm2Co17 permanent magnet

Abnormal crystal structure stability is discovered in the single-phase nanocrystalline Sm2Co17 permanent magnet. Three kinds of crystal structures, namely the rhombohedral Th2Zn17-type (2:17 R), the hexagonal TbCu7-type (1:7 H), and the hexagonal Th2Ni17-type (2:17 H), are claimed to exist at room temperature in the Sm2Co17 alloy system. The strong dependence of the magnetic properties on the structure characteristics in the single-phase Sm2Co17 alloy is interpreted in view of the atom space occupancy and the exchange coupling between substructures especially in the nanocrystalline alloy.