Thin film magnetic head for high density recording and having a leading side magnetic pole piece of variable width at the media facing surface

Embodiments of the invention provide a thin film magnetic head suitable for high density recording having a small erase band ΔE and a small fringe magnetic field, and a large recording magnetic field. In one embodiment, a width LW of a lower magnetic pole piece protuberance of a leading side magnetic pole piece, at a face in contact with a write gap layer, is made smaller than a width TW of an upper magnetic pole piece front layer of a trailing side magnetic pole piece, at a face in contact with the write gap layer, and the width of the lower magnetic pole piece protuberance adjacent to the write gap layer is made larger, in a direction from the write gap layer.