Spin-torque oscillator, magnetic head including the spin-torque oscillator, and magnetic recording and reproducing apparatus
It is made possible to provide a spin-torque oscillator that has a high Q value and a high output. A spin-torque oscillator includes: an oscillating field generating unit configured to generate an oscillating field; and a magnetoresistive element including a magnetoresistive effect film including a first magnetization pinned layer of which a magnetization direction is pinned, a first magnetization free layer of which a magnetization direction oscillates with the oscillating field, and a first spacer layer interposed between the first magnetization pinned layer and the first magnetization free layer.
1. A spin-torque oscillator comprising:
an oscillating field generating unit provided on a substrate and configured to generate an oscillating field, the oscillating field generating unit being a CPP-GMR device that includes a first stacked structure, the first stacked structure comprising a first magnetization pinned layer of which a magnetization direction is pinned, a first magnetization free layer of which a magnetization direction oscillates, and a spacer layer made of a nonmagnetic metal and interposed between the first magnetization pinned layer and the first magnetization free layer;
a magnetoresistive element provided on the substrate and electrically insulated from the oscillating field generating unit, the magnetoresistive element including a magnetoresistive effect film comprising a second magnetization pinned layer of which a magnetization direction is pinned, a second magnetization free layer of which a magnetization direction oscillates with the oscillating field, and a tunnel barrier interposed between the second magnetization pinned layer and the second magnetization free layer;
a first power supply configured to supply a current to the oscillating field generating unit, so as to cause the oscillating field generating unit to generate the oscillating field;
a second power supply configured to supply a current to the magnetoresistive effect film of the magnetoresistive element; and
a microwave extracting circuit configured to extract microwave that is output from the magnetoresistive effect film of the magnetoresistive element.
2. The oscillator according to claim 1 , wherein the first magnetization free layer of the CPP-GMR device has a larger volume than a volume of the second magnetization free layer of the magnetoresistive effect film.
3. The oscillator according to claim 1 , further comprising
a magnetostatic field generating unit placed in the vicinity of the first magnetization free layer, and configured to generate a magnetostatic field for changing frequency of the microwave.
4. A magnetic head comprising
a spin-torque oscillator according to claim 1 ,
the spin-torque oscillator serving as a reproducing device.
5. A magnetic recording and reproducing apparatus comprising a disk driver driving a magnetic disk, and a magnetic head according to claim 4 .
6. The oscillator according to claim 1 , further comprising:
a lower electrode provided under the first stacked structure;
an upper electrode provided above the first stacked structure; and
an insulating layer provided between the first stacked structure and the upper electrode, the insulating layer comprising a point contact connecting between the first stacked structure and the upper electrode.
7. The oscillator according to claim 1 , wherein the second magnetization pinned layer comprises a first magnetic layer, a second magnetic layer, and a nonmagnetic layer, the first magnetic layer and second magnetic layer being magnetically coupled via the nonmagnetic layer.