Nanostructured NdFeB films processed by rapid thermal annealing

Nanostructured NdFeB films were prepared by magnetron sputtering followed b y rapid thermal annealing at a ramp rate of 200 degrees C/s. Isotropically oriented Nd2Fe14B crystallites were formed in the films and coercivities up to 20 kOe and remanence ratios up to 0.8 were obtained. Transmission elect ron microscopy analysis shows that the majority phase of the magnetic layer in the high coercivity films consists of Nd2Fe14B nanocrystallites with an average size of about 50 nm. These nanocrystallites are believed to be sin gle-domain particles, which are responsible for the high coercivities. MFM measurements show that the domain size is about 500 nm. It is thus indicate d that the 50 nm Nd2Fe14B nanocrystallites are strongly exchange-coupled in to the 500 nm domains and the high remanence ratio originates from this exc hange coupling. (C) 1998 American Institute of Physics.