Significant improvement of soft magnetic properties for Fe(Co)BPSiC amorphous alloys by magnetic field annealing

Longitudinal field annealing (FA) is used to improve the soft magnetic properties (SMPs) of Fe83-xCoxB11P3Si2C1 (x = 0-20) amorphous alloys with high Bs of 1.65-1.76 T. These amorphous ribbons after FA exhibit pronouncedly improved SMPs, including low coercivity of 1.0-2.3 A/m and high permeability of 6.6-13 × 103 at 1 kHz. In comparison with normal annealing (NA), FA is found to be an effective process in improving the SMPs for all amorphous alloys. While NA is only effective for the alloys with Tc lower than the onset temperature of the crystallization (Tx1). It is also found that FA can change the domain sensitive direction from transversal to along the ribbon axis, and unify the easy magnetization direction. This mechanistically explains the positive effects of applied field on SMPs and structure relaxation. This paper will give a better understanding of relaxation effect on SMPs and a prospective view in formulating heat-treatment process of the thin ribbons fabricated by using a single roller melt spinning process.