Patent ID: 8254215

Claim:
A thermally-assisted magnetic recording head comprising: a medium facing surface that faces a magnetic recording medium; a main pole that has a front end face located in the medium facing surface and produces a write magnetic field for writing data on the magnetic recording medium; a waveguide including a core and a cladding, the core allowing light to propagate therethrough; and a plasmon generator having a near-field light generating part located in the medium facing surface, the plasmon generator being configured so that a surface plasmon is excited on the plasmon generator based on the light propagating through the core and the near-field light generating part generates near-field light based on the surface plasmon, wherein: the plasmon generator and the core are disposed to align in a direction of travel of the magnetic recording medium; the core has an end face that faces toward the medium facing surface and that is located away from the medium facing surface; the main pole is interposed between the end face of the core and the medium facing surface; the front end face includes a first end and a second end that are opposite to each other in a track width direction which is a direction parallel to the medium facing surface and perpendicular to the direction of travel of the magnetic recording medium; in a region sandwiched between a first virtual plane passing through the first end and perpendicular to the medium facing surface and to the track width direction and a second virtual plane passing through the second end and perpendicular to the medium facing surface and to the track width direction, an arbitrary cross section of the main pole that passes through an arbitrary point on the front end face and is perpendicular to the medium facing surface and to the track width direction has a length in a direction perpendicular to the medium facing surface; and a third length is smaller than a first length and a second length and is a minimum of the length of the arbitrary cross section obtained with the arbitrary point varied, where the first length is the length of the arbitrary cross section when the arbitrary point is located at the first end, the second length is the length of the arbitrary cross section when the arbitrary point is located at the second end, and the third length is the length of the arbitrary cross section when the arbitrary point is located at a center of the front end face in the track width direction.