Magnetic recording device and magnetic recording method utilizing assisted magnetic recording
According to one embodiment, a magnetic recording device for utilizing assisted magnetic recording includes a magnetic head, a first circuit, a second circuit, a third circuit, and a controller. The magnetic head includes a first magnetic pole, a second magnetic pole, a magnetic element, and a coil. The magnetic element is located between the first magnetic pole and the second magnetic pole. The magnetic element includes a first magnetic layer. The first circuit is configured to supply a coil current to the coil. The second circuit is configured to supply an element current to the magnetic element. The third circuit is configured to detect an electrical resistance of the magnetic element. The controller is configured to control the element current by controlling the second circuit based on the electrical resistance detected by the third circuit.
1. A magnetic recording device, comprising:
a magnetic head including a first magnetic pole, a second magnetic pole, a magnetic element, and a coil, the magnetic element being located between the first magnetic pole and the second magnetic pole, the magnetic element including a first magnetic layer;
a first circuit configured to supply a coil current to the coil;
a second circuit configured to supply an element current to the magnetic element;
a third circuit configured to detect an electrical resistance of the magnetic element; and
a controller configured to control the element current by controlling the second circuit based on the electrical resistance detected by the third circuit,
wherein
a polarity of the coil current changes at a first time in a first operation,
in the first operation, the second circuit sets the element current to a first value before a second time,
in the first operation, the second circuit changes the element current to a second value at the second time, the second value being different from the first value,
in the first operation, the second circuit changes the element current to the first value at a third time after the second time,
in the first operation, the controller can control at least one of the second time, the third time, the first value, or the second value by controlling the second circuit based on the electrical resistance detected by the third circuit,
in the first operation, the second circuit changes the element current to a third value at a fourth time before the second time, the third value being different from the first value and different from the second value,
in the first operation, the second circuit changes the element current toward the second value at a fifth time, the fifth time being after the fourth time and at or before the second time, and
in the first operation, the controller can control at least one of the second time, the third time, the fourth time, the fifth time, the first value, the second value, or the third value by controlling the second circuit based on the electrical resistance detected by the third circuit.
2. The device according to claim 1 , wherein
the first value is between the third value and the second value.
3. The device according to claim 2 , wherein an absolute value of a difference between the first value and the second value is greater than an absolute value of a difference between the first value and the third value.
4. The device according to claim 1 , wherein the magnetic element further includes:
a first magnetic pole-side nonmagnetic layer located between the first magnetic pole and the first magnetic layer; and
a second magnetic pole-side nonmagnetic layer located between the first magnetic layer and the second magnetic pole.
5. The device according to claim 4 , wherein
in the case where the first magnetic pole-side nonmagnetic layer includes a first material, and the second magnetic pole-side nonmagnetic layer includes a second material, the element current has a first orientation from the second magnetic pole toward the first magnetic pole when the element current has the first value,
the first material includes at least one selected from the group consisting of Ta, Pt, W, Ir, Mo, Cr, Tb, Mn, and Ni,
the second material includes at least one selected from the group consisting of Cu, Ag, Au, Cr, and Ru, and
in the case where the first magnetic pole-side nonmagnetic layer includes the second material, and the second magnetic pole-side nonmagnetic layer includes the first material, the element current has a second orientation from the first magnetic pole toward the second magnetic pole when the element current has the first value.
6. A magnetic recording device, comprising:
a magnetic head including a first magnetic pole, a second magnetic pole, a magnetic element, and a coil, the magnetic element being located between the first magnetic pole and the second magnetic pole, the magnetic element including a first magnetic layer;
a first circuit configured to supply a coil current to the coil;
a second circuit configured to supply an element current to the magnetic element;
a third circuit configured to detect an electrical resistance of the magnetic element; and
a controller configured to control the element current by controlling the second circuit based on the electrical resistance detected by the third circuit,
wherein
the coil current is an alternating current that includes a first frequency,
the third circuit detects an electrical signal obtained from the magnetic element,
the electrical signal includes a second frequency that is 2 times the first frequency, and
the electrical resistance corresponds to a temporal average of the electrical signal.
7. A magnetic recording device, comprising:
a magnetic head including a first magnetic pole, a second magnetic pole, a magnetic element, and a coil,
the magnetic element being located between the first magnetic pole and the second magnetic pole,
the magnetic element including
a first magnetic layer,
a first magnetic pole-side nonmagnetic layer located between the first magnetic pole and the first magnetic layer, and
a second magnetic pole-side nonmagnetic layer located between the first magnetic layer and the second magnetic pole,
the first magnetic pole-side nonmagnetic layer including one of a first material or a second material,
the second magnetic pole-side nonmagnetic layer including the other of the first material or the second material,
the first material including at least one selected from the group consisting of Ta, Pt, W, Ir, Mo, Cr, Tb, Mn, and Ni,
the second material including at least one selected from the group consisting of Cu, Ag, Au, Cr, and Ru;
a first circuit configured to supply a coil current to the coil; and
a second circuit configured to supply an element current to the magnetic element,
a polarity of the coil current changing at a first time,
the second circuit setting the element current to a first value before a second time,
the second circuit changing the element current to a second value at the second time, the second value being different from the first value,
the second circuit changing the element current to the first value at a third timed after the second time.
8. The device according to claim 7 , wherein
in the case where the first magnetic pole-side nonmagnetic layer includes the first material, and the second magnetic pole-side nonmagnetic layer includes the second material, the element current has a first orientation from the second magnetic pole toward the first magnetic pole when the element current has the first value, and
in the case where the first magnetic pole-side nonmagnetic layer includes the second material, and the second magnetic pole-side nonmagnetic layer includes the first material, the element current has a second orientation from the first magnetic pole toward the second magnetic pole when the element current has the first value.
9. The device according to claim 7 , wherein
the second circuit changes the element current to a third value at a fourth time before the second time,
the third value is different from the first value and different from the second value, and
the second circuit changes the element current toward the second value at a fifth time after the fourth time and at or before the second time.
10. The device according to claim 9 , wherein
the first value is between the third value and the second value.
11. The device according to claim 10 , wherein
an absolute value of a difference between the first value and the second value is greater than an absolute value of a difference between the first value and the third value.
12. A magnetic recording device, comprising:
a magnetic head including a first magnetic pole, a second magnetic pole, a magnetic element, and a coil,
the magnetic element being located between the first magnetic pole and the second magnetic pole,
the magnetic element including
a first magnetic layer,
a second magnetic layer located between the first magnetic layer and the first magnetic pole,
a first nonmagnetic layer located between the first magnetic layer and the second magnetic layer,
a first magnetic pole-side nonmagnetic layer located between the first magnetic pole and the second magnetic layer, and
a second magnetic pole-side nonmagnetic layer located between the first magnetic layer and the second magnetic pole;
a first circuit configured to supply a coil current to the coil; and
a second circuit configured to supply an element current to the magnetic element,
a polarity of the coil current changing at a first time,
the second circuit setting the element current to a first value before a second time,
the second circuit changing the element current to a second value at the second time,
the second value being different from the first value,
the second circuit changing the element current to the first value at a third time after the second time,
the second circuit changing the element current to a third value at a fourth time before the second time,
the third value being different from the first value and different from the second value,
the second circuit changing the element current toward the second value at a fifth time after the fourth time and at or before the second time.