Patent ID: 7492551

Claim:
A thin film magnetic head comprising: a magnetic pole layer to emit magnetic flux toward the recording medium, having a uniform-width portion which extends rearward from a recording-medium-facing surface which faces a recording medium traveling in a medium travel direction while maintaining a uniform width; a main return magnetic pole layer to return the magnetic flux emitted by the magnetic pole layer, which extends rearward from the recording-medium-facing surface on the side of the medium travel direction of the magnetic pole layer and is coupled to the magnetic pole layer in its rear end region; and a sub-return magnetic pole layer, comprising a first upper portion and a second lower portion, which is isolated from the magnetic pole layer by a gap layer, is coupled to the main return magnetic pole layer, and extends from the recording-medium-facing surface to a predetermined rearward position in a region between the gap layer and the main return magnetic pole layer, wherein a portion corresponding to the uniform-width portion in the sub-return magnetic pole layer is projected toward the uniform-width portion and is in contact with the gap layer, and wherein the orientation of a signal magnetic field is set to a direction orthogonal to a surface of the recording medium, and further wherein a saturated magnetic flux density of the first upper portion is less than or equal to a saturated magnetic flux density of the second lower portion.