Thin-film head domain structures versus Permalloy composition: strain determination and frequency response

The influence of the composition of plated Permalloy on the resulting magnetic domain structure in the upper yoke of inductive thin-film magnetic recording heads has been investigated. The response of the magnetization from four otherwise similar thin-film heads, ranging in iron content from 18 to 21% by weight, has been imaged by means of a scanning magnetooptic photometer. Radially compressive (and/or circumferentially tensile) strain is shown to exist in each of these heads about the rear magnetic closure, yielding a transition from radial to circumferential domain structures across the range of compositions. Mechanisms for the conduction of magnetic flux in each of these structures are demonstrated at 1 and 20 MHz.<
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