Magnetic properties of high Bs nanocrystalline FeCoCuNbSiB alloys

In this work, the magnetic properties and microstructures of nanocrystalline Fe_83-xCo_xCuNb₇SiB₉ (x=0-83) alloys with low Si content annealed under a transverse magnetic field are reported. Transmission electron microscope (TEM) is used to observe the microstructure of the alloys and X-ray diffraction (XRD) is carried out to identify the crystalline phases. Annealing of the specimens are done at 823 K for 3.6 ks and cooled down to 473 K at a rate of 0.017 K s^-1. D.C. B-H loops, relative permeability, coercive force and core losses are also measured. High saturation magnetic induction of 1.71 T, linear B-H loop and low core loss of 370 kW m^-3 at 100 kHz, 0.2 T are obtained at x=30 Co content. The induced magnetic anisotropy is estimated from the anisotropy field H_K determined from the d.c. B-H loops. The induced magnetic anisotropy constant for Fe₅₃Co₃₀CuNb₇SiB₈ alloy is about 140 times as large as that of Fe₈₃CuNb₇Si₉B₉.