Magnetic recording head and magnetic recording/reproducing apparatus using the same
A magnetic recording head includes a magnetic pole, a spin torque oscillator, a first shield and a second shield. The magnetic pole has an air-bearing surface. The spin torque oscillator is provided so that a first side of the spin torque oscillator faces the magnetic pole in a first direction parallel to the air-bearing surface. The first shield includes a granular magnetic material, and is provided so that two portions of the first shield sandwich the spin torque oscillator in a second direction which is parallel to the air-bearing surface and perpendicular to the first direction. The second shield is provided on a second side of the spin torque oscillator opposite to the first side.
1. A magnetic recording head comprising:
a magnetic pole having an air-bearing surface;
a spin torque oscillator provided so that a first side of the spin torque oscillator faces the magnetic pole in a first direction parallel to the air-bearing surface;
a first shield including a granular magnetic material provided so that the spin torque oscillator is sandwiched between two portions of the first shield in a second direction, the second direction being parallel to the air-bearing surface and perpendicular to the first direction; and
a second shield provided on a second side of the spin torque oscillator opposite to the first side, wherein
a resonant frequency of the granular magnetic material is higher than a frequency of a radio-frequency magnetic field generated by the spin torque oscillator.
2. The head according to claim 1 , wherein
the magnetic material includes a material selected from the group consisting of CoNiFe, CoCr, CoCrPt, CoCrTa, CoCrTaPt, CoCrTaNb, TbFeCo, CoPt, FePt, CoPd, FePd, and SmCo.
3. The head according to claim 1 , further comprising a first electrode and a second electrode, wherein
the spin torque oscillator includes:
a first magnetic layer having a coercivity lower than a magnetic field applied from the magnetic pole;
a second magnetic layer having a coercivity lower than the magnetic field applied from the magnetic pole; and
an intermediate layer provided between the first magnetic layer and the second magnetic layer,
the first electrode is provided on a side of the first magnetic layer on which the intermediate layer is not provided, and capable of passing a current through the spin torque oscillator; and
the second electrode is provided on a side of the second magnetic layer on which the intermediate layer is not provided, and capable of passing a current through the spin torque oscillator.
4. The head according to claim 1 , wherein
a magnetic grain included in the granular magnetic material satisfies a relationship of K u V<k B T, when
K u is an anisotropy energy (erg/cc);
V is a volume (cc) of the magnetic grain;
K b is a Boltzmann constant (1.38×10 −16 (erg/K)); and
T is an absolute temperature (K).
5. The head according to claim 4 , wherein
the magnetic grain included in the granular magnetic material is 3 nm or less in diameter.
6. The head according to claim 4 , wherein
an anisotropy field of the magnetic grain is 5.2 kOe or higher.
7. The head according to claim 4 , wherein
the magnetic grain includes a material selected from the group consisting of CoNiFe CoCr, CoCrPt, CoCrTa, CoCrTaPt, CoCrTaNb, TbFeCo, CoPt, FePt, CoPd, FePd and SmCo.
8. The head according to claim 4 , further comprising a first electrode and a second electrode, wherein
the spin torque oscillator includes:
a first magnetic layer having a coercivity lower than a magnetic field applied from the magnetic pole;
a second magnetic layer having a coercivity lower than the magnetic field applied from the magnetic pole; and
an intermediate layer provided between the first magnetic layer and the second magnetic layer,
the first electrode is provided on a side of the first magnetic layer on which the intermediate layer is not provided, and capable of passing a current through the spin torque oscillator; and
the second electrode is provided on a side of the second magnetic layer on which the intermediate layer is not provided, and capable of passing a current through the spin torque oscillator.
9. A magnetic recording/reproducing apparatus comprising:
a magnetic recording medium;
a magnetic recording head including:
a magnetic pole having an air-bearing surface;
a spin torque oscillator provided so that a first side of the spin torque oscillator faces the magnetic pole in a first direction parallel to the air-bearing surface;
a first shield including a granular magnetic material provided so that the spin torque oscillator is sandwiched between two portions of the first shield in a second direction, the second direction being parallel to the air-bearing surface and perpendicular to the first direction;
a second shield provided on a second side of the spin torque oscillator opposite to the first side;
a first electrode; and
a second electrode,
wherein
a resonant frequency of the granular magnetic material is higher than a frequency of a radio-frequency magnetic field generated by the spin torque oscillator;
the spin torque oscillator includes a first magnetic layer having a coercivity lower than a magnetic field applied from the magnetic pole, a second magnetic layer having a coercivity lower than a magnetic field applied from the magnetic pole, and an intermediate layer provided between the first magnetic layer and the second magnetic layer;
the first electrode is provided on a side of the first magnetic layer on which the intermediate layer is not provided, and capable of passing a current through the spin torque oscillator; and
the second electrode is provided on a side of the second magnetic layer on which the intermediate layer is not provided, and capable of passing a current through the spin torque oscillator,
a movable portion to enable a relative movement between the magnetic recording medium and the magnetic recording head so that the magnetic recording head flies above or in contact with the magnetic recording medium while facing the magnetic recording head;
a position control unit to control the magnetic recording head so that the magnetic recording head is arranged on a predetermined recording position on the magnetic recording medium; and
a signal processor to perform processing of a signal for writing on the magnetic recording medium and a signal for reading from the magnetic recording medium by the use of the magnetic recording head.
10. The recording/reproduction apparatus according to claim 9 , wherein the magnetic recording medium is a discrete track medium having tracks adjacent to each other formed through a nonmagnetic member.
11. The recording/reproduction apparatus according to claim 9 , wherein the magnetic recording medium is a discrete bit medium having recording magnetic dots isolated from each other through a nonmagnetic member and arrayed regularly.