Patent ID: 7248435

Claim:
A thin-film magnetic head comprising: a medium facing surface that faces toward a recording medium; a first pole layer and a second pole layer magnetically coupled to each other and including pole portions that are opposed to each other and disposed in regions on a side of the medium facing surface; a gap layer provided between the pole portion of the first pole layer and the pole portion of the second pole layer; a thin-film coil at least part of which is disposed between the first and second pole layers and insulated from the first and second pole layers; and a substrate wherein: the first and second pole layers, the gap layer and the thin-film coil are stacked on the substrate, and the first pole layer is located closer to the substrate than the second pole layer; the first pole layer incorporates: a first pole portion layer including the pole portion of the first pole layer; and a first yoke portion layer connected to the first pole portion layer; the second pole layer incorporates: a second pole portion layer including the pole portion of the second pole layer; and a second yoke portion layer connected to the second pole portion layer; the first pole portion layer, the gap layer and the second pole portion layer are disposed in this order on the first yoke portion layer; the second yoke portion layer is disposed on the second pole portion layer; the first pole portion layer, the gap layer and the second pole portion layer have cross sections of the same shapes, the cross sections being parallel to a top surface of the substrate; portions of the first yoke portion layer and the second yoke portion layer located at a distance from the medium facing surface are coupled to each other; an aggregate of the first pole portion layer, the gap layer and the second pole portion layer includes: a first portion having a substantially constant width that defines a track width and having an end located in the medium facing surface and the other end located at a distance from the medium facing surface; and a second portion having a width greater than the width of the first portion and coupled to the other end of the first portion; an end of the second yoke portion layer closer to the medium facing surface is located in a position that falls in a range from the medium facing surface to a position in the second pole portion layer at which an interface between the first portion and the second portion is located; the second yoke portion layer has a width greater than a maximum width of the second pole portion layer taken in the second portion; where the width of the first portion is W and the distance from the medium facing surface to the interface between the first portion and the second portion is L, L/W falls within a range of 2 to 5 inclusive; and where the area of each of the cross sections of the first pole portion layer, the gap layer and the second pole portion layer is S, S/(W×L) falls within a range of 5 to 40 inclusive.