Studies on structural and magnetic properties of ball milled Nd2Fe14B intermetallic powders

摘要

The effect of ball milling on the structural and magnetic properties of Nd2Fe14B intermetallic compound was studied by X-ray diffraction (XRD) and magnetisation measurements. The average crystallite size calculated from the XRD patterns on the powders ball milled (BM) for 40 h is seen to lie in the range of 25?50 nm, whereas the particle size estimated using atomic force microscopy imaging is in the range of 40?100 nm. Magnetisation and anisotropy of BM Nd2Fe14B were found to decrease with increasing milling time. This was explained based on the increased defect density with milling and reduction in particle size. Using a differential scanning calorimeter, recovery and recrystallisation of the BM samples were studied during heating. The Curie temperature was found to decrease with increasing milling time. The BM samples were annealed at 1173 K for 15 min, and XRD and magnetisation studies were conducted. Mechanisms of ?-Fe separation and change in intrinsic properties during milling and annealing of milled powders are discussed.