The change of magnetic properties in nanocrystalline Fe88Zr7B4Cu1 alloy by cooling rate

We have investigated the effect of cooling rate, followed immediately after the isothermal annealing, on the magnetic properties of melt-spun Fe88Zr7B4Cu1 alloy. As the cooling rate is increased, the effective permeability, 2×104, improved by 50% on annealing at around 650 °C. The remanence ratio is also found to concomitantly decrease with the increasing cooling rate. The increase of permeability and decrease of remanence ratio are consistent with the expected suppression of the induced magnetic anisotropy. From an analysis of the transmission electron microscopy micrographs, and the x-ray diffraction spectral intensities, we find that the volume fraction of the amorphous matrix to that of the nanocrystallized magnetic entities to be about 20%, at which the permeability has the maximum value for this system. Scanning electron microscopy and antiferromagnetic investigations show a much smoother surface morphology with a finer grain distribution in the rapidly quenched sample.