Conventional magnetic properties and barkhausen noise in ferromagentic metallic glasses

Abstract

The influence of heat treatment on conventional magnetic properties and Barkhausen Noise were studied in ferromagnetic amorphous $Fe_{40}Ni_{38}Mo_4B_{18}$ during a half magnetization cycle for both amorphous and crystallized states. The coercivity, $H_c$, was low in the amorphous specimen and maximum as the crystallization starts, and decreased with further annealing. The differential permeability near the $H_c,$ $μ_c$, was high in the amorphous specimen and minimum at the onset of crystallization, then increased with annealing. The single peak behavior of BN envelope was a common feature in both amorphous and crystallized specimens, and the variation of peak height with heat treatment were similar to that of $μ_c$. The magnetic anisotropy energy constant, $K_u$, was lowest when the crystallite started to nucleate in the amorphous specimen, and increased as the crystallite size grows. The difference between ribbon and transverse directions of BN characteristics such as BN energy, peak height of BN envelope, $H_p$, and corresponding field strength to $H_p$ respectively was the lowest at the onset of crystallization, and increased with $K_u$. The model was proposed to account for the linear relationship between the magnetic anisotropy energy constant detected by torque measurement and that of evaluated by BN measurement. The effect of heat treatment with/without a magnetic field on conventional magnetic properties and Barkhausen noise (BN) of toroidal core and square specimen of amorphous $Fe_{78}B_{13}Si_9$ respectively was investigated. The B-H hysteresis loops of all toroidal cores were square type regardless of annealing with/without magnetic field. The coercivity, $H_c$, and hysteresis loss, $W_h$, with maximum at as-quenched toroidal core decreased with annealing temperature up to 390℃ for both annealing with/without magnetic field, and increased with further annealing. However the $H_c$ and $W_h$ of field annealed toroidal core were lower than that of ann...