Harmonic analysis method for gap width evaluation

The data retrieval resolution of spin-valve reading head is a function of the spacing between the shield layer and the free layer of the spin-valve head - the head gap. Spin-valve head is of multi-layer structure. The layer thickness variation among different wafers leads to the variation of the gap length. Therefore it is important to develop a suitable methodology for testing and evaluating the gap length fluctuation not only during the head fabrication process but also at the magnetic integration level. This paper reports a novel method for the quantitative evaluation of the gap length fluctuation among different heads. The proposed method proved to be simple and easy for implementation.