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 annealed without a magnetic field for all annealing temperature. Annealing the toroidal core without a magnetic field substantionally increased the remanent magnetic induction, $B_r$ and squareness $B_r/B_s$, and further increased by magnetic field annealing for annealing temperature tested.
Single peak behavior of BN envelopefor parallel(L direction) and transverse (T direction) field directions with respect to ribbon axis respectively was observed for as-quenched square specimen. Two peaks behavior of BN envelope, corresponding domain nucleation and annihilation process, for L direction was a common feature in the specimen annealed up to 390℃ with a magnetic field, and new peak appeared between them with further annealing. The single peak of BN envelope for T direction in the temperature range up to 380℃ splits into two peaks at 390℃ and several peaks with further annealing. The peak height of BN envelope and BN energy in field annealed specimen decrease with annealing temperature same as that of f hysteresis loss.
The two peaks behavior of BN envelope for L direction and single peak for T direction were obderved for the specimen annealed without a magnetic field. The peak height of BN envelope and BN energy of the specimen annealed without a magnetic field were higher than those of field annealed specimen.
The dependence of power spectrum on frequency with annealing temperature and magnetizing frequency was characterized by the clustering and overlapping nature of the Barkhausen noise, and was determined by participating domain dynamics.
강자성을 나타내는 비정질 자성재료에서의 열처리후 자기적 성질과 바크하우젠 노이즈에 관한 연구이었다. 비정질 자성재료 $Fe_{40}Ni_{38}Mo_4B_{18}$에서는 비정질상과 미세결정상에 관한 연구로 두 상태의 자기적 성질과 바크하우젠 노이즈의 차이를 미세구조와 그와 관련한 자구 동역학에 의해 설명하였다. 비정질 자성재료 $Fe_{78}B_{13}Si_9$에 서는 비정질상태에서의 연구로 자기손실 에너지와 바크하우젠 노이즈 에너지를 고려해 시편의 자기적성질의 향상을 위한 최적열처리 조건으로 무자장 열처리보다는 시편을 포화자화시키는 자장세기로의 자장중 열처리임을 밝혔다. 이 시편의 바크하우젠 노이즈 파워스펙트럼의 주파수 의존성은 자장의 유무나 온도등 열처리조건에 의해 결정된 자구동역학에 의해 결정되었다. 본 연구에서 제시된 바크하 우젠 노이즈 외피전압에 관한 모델과 바크하우젠노이즈의 외피전압을 측정함으로써 평가된 자기이방성 에너지 모델등 두가지 모델은 실험결과와 좋은 일치를 보였다.
