Magnetic field sensor using spin polarized current
View Patent ↗A hybrid magnetic-semiconductor structure can be used as a magnetic field sensor. The hybrid device uses ferromagnetic materials for implementing a variable spin resistance. An external magnetic field can change the magnetization state of the device by orienting the magnetization of the ferromagnetic layers to be parallel or antiparallel, thus changing the resistance of the device to a current of spin polarized electrons.
1. A magnetic field sensor device comprising:
a first ferromagnetic region having a first coercivity and a first fixed magnetization state;
a second ferromagnetic region having a second coercivity smaller than said first coercivity, and which second ferromagnetic region has a second magnetization state which is configured to respond to a magnetic field generated by magnetically recorded data;
a high electrical impedance region situated between said first ferromagnetic region and said second ferromagnetic region;
wherein the sensor device has a variable magnetic resistance based on a relationship between said first magnetization state of said first ferromagnetic region and said second magnetization state of said second ferromagnetic region such that a value of a spin polarized current conducted in the sensor device varies in accordance with said magnetically recorded data.
2. The magnetic field sensor of claim 1 , wherein said high electrical impedance region is a channel of a silicon based transistor.
3. The magnetic field sensor of claim 1 , further including a gate for controlling a conductivity of said channel.
4. The magnetic field sensor of claim 1 , wherein both said first ferromagnetic region and said second ferromagnetic region overly a silicon substrate.
5. The magnetic field sensor of claim 1 , wherein said first ferromagnetic region has a first shape which includes a first curved edge followed by first straight edge.
6. The magnetic field sensor of claim 1 , wherein said second ferromagnetic region includes a layer of at least one of a ferromagnetic metal, a semimetal, a semiconductor, and/or a perovskite.
7. The magnetic field sensor of claim 1 , wherein said first ferromagnetic region is larger in size for the magnetic field sensor than said second ferromagnetic region.
8. The magnetic field sensor of claim 1 , wherein said first ferromagnetic region operates as a spin current injector and said second ferromagnetic region operates as a spin current detector.
9. The magnetic field sensor of claim 1 , wherein said first ferromagnetic region includes a Heusler alloy.
10. The magnetic field sensor of claim 1 , wherein said first ferromagnetic region includes at least one of permalloy, cobalt, iron and/or FeCo.
11. The magnetic field sensor of claim 1 , wherein said second ferromagnetic region includes a Heusler alloy.
12. The magnetic field sensor of claim 1 , wherein said second ferromagnetic region includes at least one of permalloy, cobalt, iron and/or FeCo.
13. A read head for use with magnetic recording media comprising:
a first ferromagnetic region having a first fixed magnetization state;
a second ferromagnetic region having a second magnetization state which is variable and configured to respond to a magnetic field generated by magnetically recorded data;
a high electrical impedance region situated between said first ferromagnetic region and said second ferromagnetic region, which high electrical impedance region can conduct a spin polarized current;
wherein a relationship between said first magnetization state of said first ferromagnetic region and said second magnetization state of said second ferromagnetic region can be set in response to said magnetically recorded data, such that a value of said spin polarized current can be read to determine said magnetically recorded data.
14. The read head of claim 13 , wherein said high electrical impedance region can be controlled by a gate to have a high impedance or a low impedance to said spin polarized current.
15. The read head of claim 13 , wherein both said first ferromagnetic region and said second ferromagnetic region overly a silicon substrate.
16. The read head of claim 13 , wherein said high electrical impedance region is part of a semiconductor substrate.
17. The read head of claim 13 , wherein said second ferromagnetic region has n separate stable states, where n>2.
18. The read head of claim 13 , wherein said second ferromagnetic region and said first ferromagnetic region are separated by a distance on the order of a few electron mean free path lengths.
19. The read head of claim 18 , wherein said distance is between about 0.1 microns to 1 micron.
20. The read head of claim 13 , wherein said spin polarized current is injected with an orientation that is along a magnetization orientation of said first and/or second ferromagnetic region.
21. The read head of claim 13 , wherein said second ferromagnetic region includes a layer of at least one of a ferromagnetic metal, a semimetal, a semiconductor, and/or a perovskite.
22. The read head of claim 13 wherein said first ferromagnetic region is larger in size for the read head than said second ferromagnetic region.
23. The read head of claim 13 wherein said first ferromagnetic region operates as a spin current injector and said second ferromagnetic region operates as a spin current detector.
24. The read head of claim 13 , wherein said first ferromagnetic region includes a Heusler alloy.
25. The read head of claim 13 , wherein said first ferromagnetic region includes at least one of permalloy, cobalt, iron and/or FeCo.
26. The read head of claim 13 , wherein said second ferromagnetic region includes a Heusler alloy.
27. The read head of claim 13 wherein said second ferromagnetic region includes at least one of permalloy, cobalt, iron and/or FeCo.
28. A spin polarized electron current magnetic field sensing device comprising:
a first ferromagnetic region having a first coercivity;
a second ferromagnetic region having a second coercivity larger than said first coercivity;
wherein a spin polarized current in the spin polarized electron current sensing device varies in accordance with a relationship between a first magnetization state of said first ferromagnetic region and a second magnetization state of said second ferromagnetic region, which relationship can be altered by a magnetic field sensed by such device;
an enhancement layer situated between said ferromagnetic region and said second ferromagnetic region, which enhancement layer is adapted to increase a polarization efficiency for said spin polarized current.
29. The spin polarized electron current magnetic field sensing device of claim 28 , wherein said enhancement layer reduces an ohmic contact resistance between said first ferromagnetic region and a high impedance region.
30. The spin polarized electron current magnetic field sensing device of claim 28 , wherein said enhancement layer includes metal, and increases a polarization efficiency of a current injector used to generate polarized current with a predefined spin.
31. The spin polarized electron current magnetic field sensing device of claim 28 , further including an insulating layer situated between at least a portion of said second ferromagnetic region and said enhancement layer.
32. The spin polarized electron current magnetic field sensing device of claim 31 , wherein said data value can have n different values, where n>2.