sitive layer in dependency of the thickness of the underlying metal layer of FIG. 1;FIG. 7 is a cross-sectional view illustrating a shield-type MR head to which the embodiment of the present invention is applied;FIG. 8 is a cross-sectional view illustrating another shield-type MR head to which the embodiment of the present invention is applied; andFIGS. 9A and 9B are a plan view and a cross-sectio