Mössbauer spectroscopy research on magnetic softening of Fe ₈₄ B ₁₀ C ₆ amorphous alloy during low-temperature annealing

Abstract

The mechanism of magnetic softening in Fe84B10C6 amorphous alloys annealed at a temperature below the crystallization temperature has been investigated by Mössbauer spectroscopy. With the prolongation of annealing time, saturation flux density increases gradually but coercivity firstly declines to a minimum and then increases drastically. All the modulations of local structure strengthen the magnetic exchange between Fe neighbor atoms during low-temperature annealing. The structural relaxation at the early stage of annealing including annihilation of excess free volume and residual stress rotates the easy axis to the ribbon plane and weakens magnetic anisotropy, while the subsequent structural relaxation contributing to chemical inhomogeneity results in the inverse situation. Thus, appropriate annealing can magnetically soften amorphous alloys. For the Fe84B10C6 amorphous alloy, soft magnetic properties are optimized when annealed at 493 K for 100 s.