Barkhausen noise in ferromagnetic materials

Abstract

The analysis of the Barkhausen noise envelope and conventional magnetic properties have been applied to study microstructural 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$^\circ$ 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 increase...