The analysis of the Barkhausen noise envelope and conventional magnetic properties have been applied to study microstructual dependence of the magnetization process in the ferromagnetic materials of mild steel, HiB-6 and conventional 3% Si-Fe, and 78.5% Permalloy. The structural variables investigated have included plastic strain, grain orientation, and angular dependence with respect to rolling texture of uniaxial and multiaxial magnetic anisotropy.
The rectified Barkhausen noise envelope, induction rate dB/dt signal, $d^2B/dt^2$ signal and hysteresis curve were measured simultaneously by the encircling type prove. The two peaks in the Barkhausen noise envelope and the sharp changes of permeability of the annealed 3% Si-Fe and unstrained mild steel at the knee regions of hysteresis curve, corresponding to the 180˚domain nucleation and annihilation processes, are due to the larger nucleation field than the retarding field of defects. The single peaked noise envelope and permeability of the plastically strained mild steels, cold- worked 3% Si-Fe and Permalloy at the coercive field are attributed to the larger retarding field of defects than the nucleation field due to easy nucleation of reverse domain.
The two peaks in the noise envelope of unstrained mild steel disappeared gradually as the maximum magnetic field strength decreased due to lesser domain nucleation and annihilation process in the under-saturated state. The increase of the coercive field with plastic strain was attributed to the increment of dislocation density. The variation of the Barkhausen noise energy was explained by means of the energy released during domain nucleation and annihilation, and hysteresis loss by pinning effects of moving wall respectively.
The two peaks in the noise envelope and permeability derivation of HiB-6 were a higher amplitude than that of conventional grain-oriented 3% Si-Fe because the critical field strength for the nucleation at grain boundary increases with the reduction of misorientation angle between the adjacent grains. The HiB-6 were a higher maximum induction and lower coercive field than that of conventional specimen.
The peak amplitude of the single peaked noise envelope and permeability in the cold-worked 78.5% Ni Permalloy of uniaxial magnetic anisotropy at the coercive field decreased with the specimen angle due to the reduction of driving foece of domain wall. The angular dependence of maximum induction, the noise envelope and permeability in HiB-6 of multiaxial anisotropy were explained in terms of the volume fractions for the nucleation of domain magnetized in (010) and (100) directions, and main domain of (001) direction during magnetization process.
The variation of frequency spectrum with plastic deformation, rolling texture, and magnetizing frequency were characterized by the clustering and overlapping nature of the Barkhausen noise.
Finally, domain potential wall energy model for the release of the Barkhausen noise and permeability, in terms of the fluctuating and averaged domain wall velocity respectively, have been proposed to account for the behavior of the noise envelope in the annealed and cold-worked specimen.
강자성체의 자화과정중 Barkhausen noise envelope, induction rate dB/dt, $d^2B/dt^2$ 신호를 측정하였다. annealed연강, 3% Si-Fe와 냉각압연된 Permalloy에서 각기 Barkhausen noise envelope 의 두 peak와 단일 peak현상은 자벽 potential energy model 에 의하여 180˚자벽의 생성과 소멸로서 설명하였다. 또한 연강의 소성에 따른 보자력, hysteresis loss, Barkhausen noise energy 의존성을 조사하였다. HiB-6와 Conventional grain-oriented 3% Si-Fe 시편에서 Barkhausen noise와 자기특성을 비교 분석하였으며, 단일자기 Anisotropy을 갖는 냉각압연된 78.5% Ni Permalloy와 3개의 자기 Anisotropy을 갖는 HiB-6에서 시편 각도에 따른 Barkhausen noise와 자기특성들을 조사 분석하였다. Barkhausen noise의 Power Spectrum은 noise의 Clustering와 Overlapping으로서 적절히 설명되었다.
