Non-contact current sensor
A non-contact current sensor includes a spin valve structure ( 2 ), an electrical unit ( 4 ) that applies a varying current to the spin valve structure ( 2 ), and a resistance reading unit that electrically reads out a resistance value of the spin valve structure ( 2 ). When a current-induced magnetic field is detected, a coercive force of a free layer ( 14 ) is configured to be larger than the current-induced magnetic field as a detection target, and the electrical unit ( 4 ) allows the magnetization directions of a pinned layer ( 12 ) and the free layer ( 14 ) to transition between a mutually parallel state and a mutually anti-parallel state by applying the current to the spin valve structure ( 2 ). The resistance reading unit ( 5 ) detects a threshold value corresponding to the transition.
1. A method for detecting a current-induced magnetic field in a non-contact current sensor, the method comprising:
detecting, with a spin valve structure, a magnetic field induced by a current flowing through a wire adjacent to the spin valve structure, the spin valve structure comprising:
a free layer having a direction of magnetization and a coercive force that is larger than the current-induced magnetic field;
a pinned layer having a direction of magnetization; and
a nonmagnetic layer arranged between the free layer and the pinned layer;
applying, with an electrical unit, a current to the spin valve structure to cause the direction of magnetization of the pinned layer and the direction of magnetization of the free layer to transition between a mutually parallel state and a mutually anti-parallel state; and
electrically reading, with a resistance reading unit, a resistance value of the spin valve structure if the current-induced magnetic field is detected.
2. The method of claim 1 , wherein said electrically reading a resistance value of the spin valve structure comprises detecting, by the resistance reading unit, a threshold value of the current corresponding to the transition between the mutually parallel state and the mutually anti-parallel state to determine the resistance value at the transition.
3. The method of claim 2 , wherein the threshold value of the current changes based, at least in part, on a magnitude of the current-induced magnetic field.
4. The method of claim 3 , wherein the threshold value of the current is changed by changing an electric bias value with the electrical unit.
5. The method of claim 1 , wherein the resistance value of the spin valve structure electrically read by the resistance reading unit corresponds with one of:
a first logical value that is associated with the mutually parallel state direction of magnetization of the pinned layer and the free layer; or
a second logical value that is associated with the mutually anti-parallel state direction of magnetization of the pinned layer and the free layer.
6. The method of claim 1 , wherein the spin valve structure is one of a plurality of spin valve structures connected in series, and wherein each of the plurality of spin valve structures has a different area.
7. The method of claim 1 , wherein said applying a current to the spin valve structure comprises applying a plurality of pulses by a pulse source of the electrical unit, and wherein the pulse source changes the pulse height every time one of the plurality of pulses is applied.
8. The method of claim 1 , wherein said applying a current to the spin valve structure comprises applying a plurality of pulses by a pulse source of the electrical unit, and wherein the pulse source changes the pulse width every time one of the plurality of pulses is applied.
9. The method of claim 1 , wherein the nonmagnetic layer is metal.
10. The method of claim 1 , wherein the nonmagnetic layer is an insulator.
11. A spin valve structure configured to detect a current-induced magnetic field, the spin valve structure comprising:
a free layer having a direction of magnetization and a coercive force that is larger than the current-induced magnetic field;
a pinned layer having a direction of magnetization; and
a nonmagnetic layer arranged between the free layer and the pinned layer;
wherein the spin valve structure is configured to receive a current to cause the direction of magnetization of the pinned layer and the direction of magnetization of the free layer to transition between a mutually parallel state and a mutually anti-parallel state.
12. The spin valve structure of claim 11 , wherein the directions of magnetization of the pinned layer and the free layer transition between a mutually parallel state and a mutually anti-parallel state if a current is applied to the spin valve structure.
13. The spin valve structure of claim 11 , wherein the nonmagnetic layer is metal.
14. The spin valve structure of claim 11 , wherein the nonmagnetic layer is an insulator.
15. The spin valve structure of claim 11 , wherein the free layer, the pinned layer, and the nonmagnetic layer are stacked using a sputtering method.
16. The spin valve structure of claim 11 , wherein the pinned layer is CoFeB/Ru/CoFe/IrMn.
17. The spin valve structure of claim 11 , wherein the non-magnetic layer is MgO.
18. The spin valve structure of claim 11 , wherein the free layer is CoFeB.
19. The spin valve structure of claim 11 , wherein an interlayer insulating film is formed on the free layer, the pinned layer, and the non-magnetic layer.
20. The spin valve structure of claim 19 , wherein the interlayer insulating film is SiO2.