Soft magnetic properties of high-temperature nanocrystalline alloys: Permeability and magnetoimpedance.

摘要

The technological applicability of FeCoNbBCu alloys is suggested in terms of measurements ofroom temperature magnetoimpedance and temperature dependence of magnetic permeabilitymr.Results for the Fe78-xCoxNb6B15Cu1alloy series show that room temperature soft magneticproperties are enhanced in the lowest Co containing alloy (mr;10 500 and magnetoimpedance ratio;60% at 1 MHz!. However, permeability exhibits a smoother thermal dependence in the alloys withmedium and high Co content. A tradeoff between magnetic softness and its thermal stability revealsthe alloy with 39 at. % Co as the most suitable composition among those studied, characterized bya temperature coefficient of;0.02%/K from room temperature up to 900 K. This value is 1 orderof magnitude smaller than those observed for FeSiBCuNb~FINEMET-type!alloys and Mn ferritesand extended over a much wider temperature range than in these materials.