Mossbauer study on intergranular phases in the bcc-Fe/NdFeB nanocomposite alloys

Magnetic properties of the intergranular phase in the bcc-Fe/NdFeB nanocomposite alloys containing Nb and Co were investigated with Mossbauer spectroscopy. The alloys were prepared with melt-spinning and post-annealing method. It is revealed that the intergranular phase is not amorphous as considered so far and consists of several thin layers outside the nanoscale grains of bcc-Fe and Nd2Fe14B. The hyperfine field in the layer on the surface of the grain is rather strong and the structure of this layer is similar to the grain. The field in the outer layers is reduced because the structure becomes indistinct gradually as the layer is apart from the grain. The high remanence and coercive field of the nanocomposite alloys may originate from the magnetic coupling between grains via the intergranular ferromagnetic phase. (C) 2000 American Institute of Physics. [S0021-8979(00)24008-5].