The residual amorphous phase in nanocrystalline soft magnetic FeSiCuNbB

In order to synthesize separately the residual amorphous phase present in rapidly quenched nanocrystalline FeSiCuNbB ribbons, powders of nominal composition Fe/sub 92-x/Nb/sub 8/B/sub x/ with x=19...45 as well as Fe/sub 63/Nb/sub 9/B/sub 28/ and Fe/sub 55/Nb/sub 12/B/sub 33/ were mechanically alloyed for amorphization and annealed at 540/spl deg/C for structural relaxation. The amorphous powder products show crystallization temperatures T/sub x1/ and T/sub x2/ increasing with B content from 600 to 750/spl deg/C and 750 to 950/spl deg/C respectively. The Curie temperature and also room-temperature saturation polarization show maximum values of about 140/spl deg/C and 0.8 T at a B content of 25 at.%. Compared to that, the Curie temperature of the amorphous grain boundary phase of same composition in nanocrystalline FeSiCuNbB is by at least 100/spl deg/C higher, presumably caused by exchange-field penetration from the adjacent /spl alpha/-FeSi nanocrystallites.