Size-dependent spin-reorientation transition in Nd2Fe14B nanoparticles

a r t i c l e i n f o a b s t r a c t It is well known that some ferromagnetic properties like Curie temperature are size dependent. In this Letter we will report that the spin-reorientation temperature of Nd 2 Fe 14 B material is also size dependent. By using a surfactant-assisted ball milling technique, Nd 2 Fe 14 B nanoparticles with different size about 6, 20 and 300 nm were successfully obtained. Spin-reorientation transition temperature of the NdFeB nanoparticles was then determined by measuring the temperature dependence of DC and AC magnetic susceptibility. It was revealed that the spin-reorientation transition temperature (T sr) of the nanoparticles is strongly size dependent. T sr of the 300 nm particles is lower than that of the bulk raw material while the T sr of the 20 nm particles is significantly lower than that for the 300 nm particles. The physics behind this size dependence is discussed.