Magnetic head comprising pole including nonmagnetic layer and disk drive with the same

A magnetic head for perpendicular magnetic recording, comprising:

• a main pole configured to apply a recording magnetic field perpendicular to a recording layer of a recording medium;
• a return pole opposed to a trailing side of the main pole across a write gap and configured to return magnetic flux from the main pole to form a magnetic circuit in conjunction with the main pole;
• a coil configured to excite magnetic flux in the magnetic circuit;
• a spin-torque oscillator located between respective facing surfaces of the return pole and an end portion of the main pole on the recording-medium side and configured to produce a high-frequency magnetic field;
• a current source configured to apply current to the spin-torque oscillator through the return and main poles;
• and
• a nonmagnetic layer provided in at least one of the poles and extending from a facing surface of the at least one of the poles, which faces the spin-torque oscillator, into the at least one of the poles.