Structure and size-dependent properties of NdFeB nanoparticles and textured nano-flakes prepared from nanocrystalline ribbons

Abstract

A surfactant-assisted ball milling technique was employed to synthesize NdFeB nanoparticles and nanoflakes from melt-spun nanocrystalline powders. The microstructure evolution during ball milling and the particle size dependent magnetic properties were investigated. The formation mechanism of submicrometre flakes and textured nanoflakes were discussed. The surfactant and ball-to-powder weight ratio played a crucial role in the formation of nanoflakes. The coercivity of the particles decreased with decreasing particle size. Significant room temperature coercivity HC higher than 300 kA m−1 was obtained in the nanoparticles with a mean size of ~20 nm. The spin reorientation temperature was found to decrease with reducing particle size, which may be related to the change in magnetocrystalline anisotropy caused by the induced strain during ball milling.