Magnetic head having an Fe-Ni-X layer

A magnetic head comprising a lower core layer, an upper core layer, a non-magnetic gap layer positioned between the lower core layer and the upper core layer, and a coil layer, provided surrounding a magnetic coupling portion between the lower core layer and the upper core layer, for applying a magnetic field to the lower core layer and the upper core layer,

• wherein the upper core layer, made of an FeNiX alloy (X being an element of one of rhenium Re and molybdenum Mo), and defined by a lower surface facing the lower core layer and an upper surface opposed to the lower surface, comprises a rising portion that gradually rises from a side opposing a recording medium toward a deeper side of the head with the lower surface and the upper surface gradually parting away from the lower core layer, and a core leading portion where the lower surface and the upper surface extend in parallel with the lower core layer, and
• wherein a concentration difference of the upper core layer between a concentration of iron by weight percent and a concentration of the element X by weight percent is smaller at any backward position at a thickness center than at any frontward position, located more frontward than the backward position, at the thickness center in each of the leading portion and the rising portion where the thickness center lies at a half-thickness level of the thickness of the upper core layer between the upper surface and the lower surface thereof, the thickness being along a direction of line normal to the lower surface.