Non-contact current sensor

• US 9,939,466 B2
• Filed: 05/13/2015
• Issued: 04/10/2018
• Est. Priority Date: 07/27/2009
• Status: Active Grant

• Current Assignee: III Holdings 3, LLC
• Original Assignee: III Holdings 3, LLC
• Inventors: Ogimoto, Yasushi
• Primary Examiner(s): Phan, Huy Q
• Assistant Examiner(s): FREDERIKSEN, DAVID B
• Application Number:
  US14/711,583
• Publication Number:
  US 20150247884A1
• Time in Patent Office: 1,063 Days
• CPC Class Codes: G01R 15/148 involving the measuring of a magnetic field or electric field G01R15/18, G01R15/20, G01R15/24, G01R15/26 take precedence
• CPC Class Codes: G01R 15/205 using magneto-resistance devices, e.g. field plates
• CPC Class Codes: G01R 33/093 using multilayer structures, e.g. giant magnetoresistance sensors thin magnetic films H01F10/00
• CPC Class Codes: G01R 33/098 comprising tunnel junctions, e.g. tunnel magnetoresistance sensors

Abstract

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.

Claims

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.