Repeatability of Barkhausen transitions in thin films

Barkhausen transition fields for anisotropic Permalloy films, measured by the resonance enhancement technique, were found to be a function of the maximum field to which a sample was subjected before the occurrence of these transitions. In these experiments, the Barkhausen transitions were monitored after repeated cycling of the field applied along the easy axis between given maximum positive and negative values to obtain a nearly repeatable initial state. For a film with an H/sub c/ of 1.4 oe, the Barkhausen transition fields for repeated passes through Hc differed from each other by no more than 4.2% if the field was cycled between /spl plusmn/48 oe. For a cycling field between /spl plusmn/22.5 oe, the corresponding deviation increased to 9.9%.<
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