The Barkhausen noise, its frequency spectrum and the hysteresis loops of cold-rolled 78% permalloy have been studied during magnetization cycle at different magnetizing frequencies.
The hysteresis loss did not change at different magnetizing frequencies (0.05 Hz, 10 Hz and 90 Hz), but the average amplitude of Barkhausen noise was larger at higher magnetizing frequency (in the range of 0.01 - 1Hz), that is, Barkhausen noise have the tendency to be clustered more strongly at higher magnetizing frequency.
The magnitude of the frequency spectrum was greatest near Hc, that is, the clustering mature of Barkhausen noise is predominant at the steepest parts of the hysteresis loop.
The hysteresis loop and Barkhausen noise of deformed mild steel were measured. When the deformation became more severe, the magnetic property was harder.
This is supposed to be due to the increase of dislocation densities which act as barriers to the domain wall motion, and this was confirmed by the measurement of Barkhausen noise, average amplitude of which increased when the deformation became more and more severe.
냉압연된 78.5% permalloy와 변형된 mild steel에서 변형량에 따른 자성의 변화를 조사하기 위하여 자기이력곡선의 해당하는 Barkhausen Noise의 frequency spectrum과 mean amplitude 와 Ring down count 를 측정하였으며 자화 frequency 가 이에 미치는 영향을 조사하기 위해서 0.01Hz 까지 변화시켰다. 실험결과 Barkhausen Noise의 frequency spectrum은 자기이력곡선상의 미분변화율 변화가 급격한 곳에서 amplitude가 최대였으며 자화 frequency가 증가할 때 mean amplitude는 증가하였으나 ring down count는 감소하였다. 또 변형의 양이 증가함으로서 항자력 (Hc)은 증가하였고 Barkhausen Noise의 mean amplitude도 증가하였다.