Fluctuation of domain wall motions and its control in 50% Ni-Fe tape cores

An apparatus was developed which could display simultaneously the domain wall motions at many points of a magnetic core surface on an oscilloscope. It was observed that the motion of the domain walls fluctuated from cycle to cycle in an alternating field. It was found that these fluctuations could be reduced markedly by superposition of a pulse on the alternating field. The pulse was set at the saturating interval of the core in every half-cycle. The polarity of the pulse was chosen to further drive the core to saturation. A reduction ratio of 10:1 could be obtained easily with magnetically annealed cores.