Size-dependent magnetic properties in Nd–(Fe, Mn)–B nanoparticles

The size dependence of the magnetic properties and in particular the Curie temperature, the spin reorientation temperature, and the magnetocrystalline anisotropy have been investigated in Nd2Fe11Mn3B nanoflakes (thickness below 200 nm) and nanoparticles (5–13 nm) synthesized by high-energy ball milling. Magnetization and susceptibility measurements showed for the first time in rare-earth intermetallic compounds a much higher Curie temperature in nanoparticles as compared to bulk, which can be explained by finite-size scaling. The particles and flakes also showed lower coercivities and spin reorientation temperatures which can be attributed to their lower magnetocrystalline anisotropy. In the 4.8 nm particles, the magnetocrystalline anisotropy is estimated to be nearly half of the bulk value.