Low core losses and soft magnetic properties of Fe–Al–Ga–P–C–B–Si glassy alloy ribbons with large thicknesses

Abstract

The structure, soft magnetic properties, and core losses were investigated for a Fe77Al2.14Ga0.86P8.4C5B4Si2.6 glassy alloy with a sheet thickness in a wide range from 30 to 240 μm prepared by the melt-spinning technique. The maximum thickness (tmax) for glass formation and the thermal stability (ΔTx) of the supercooled liquid region defined by the difference between the crystallization temperature (Tx) and the glass transition temperature (Tg) are about 220 μm and 35 K, respectively. The saturation magnetization (σs) of this glassy alloy is about 1.5 T. The effective permeability at 1 kHz is as high as 12 000 in a thickness of 30 μm and it maintains high values above 4400 up to a thickness of tmax. The coercive force is kept at a low level, under 3 A/m up to tmax. This glassy alloy also shows low core loss values of 0.1–0.3 W/kg at f=50 Hz and Bm=1.0 T in the thickness from 30 to 220 μm. On the other hand, a Fe78Si9B13 amorphous alloy shows almost the same low core losses as that of the glassy alloy only in a thickness of less than 70 μm. The difference between the dependence of the soft magnetic properties and the core loss on the thickness of these alloys should arise from their difference in ability of glass forming. The Fe–Al–Ga–P–C–B–Si glassy alloys should be very useful for inductive applications because of their thick ribbon shape and good soft magnetic properties in addition to low core loss.