Microstructures and high-frequency magnetic properties of nanocrystalline (Fe1-xCox)78.4Nb2.6Si9B9Cu1 soft magnetic alloys

Microstructures and high-frequency magnetic properties were investigated for amorphous (Fe1-xCox)(78.4)Nb2.6Si9B9Cu1(x=0.35, 0.5, 0.65) alloys annealed at 490 degrees C for 0.5 h under vacuum atmosphere (1 X 10(-3) Pa). XRD analysis showed that the alpha-FeCo (Si) crystallites of about 15 nm in diameter precipitated from the amorphous matrix after annealing. With increasing Co content, the lattice parameter of a-FeCo(Si) crystallites decreased. Pseudo-Voigt2 function was used for fitting the XRD patterns in order to estimate the crystalline volume fraction. The mean composition of the residual amorphous matrix was estimated according to crystalline volume fraction and lattice parameter. Permeability-frequency spectra from 10 kHz to 10 MHz of the nanocrystalline alloys showed that with increasing Co content, the initial permeability decreased and resonance frequency remarkably increased. The equation of domain wall motion and the domain wall pinning mechanism were used to analyze the relationship between high-frequency magnetic property of the alloy and Co content.