Magnetic tunnel barriers and related heterostructure devices and methods
Disclosed herein are devices, systems, and methods that provide improved tunneling magnetoresistance (TMR) through the use of innovative device structures and heterostructure layers therein. Particularly, two or more magnetic layers form a heterostructure core of the switching device, with control of current passing through the heterostructure determined by an applied magnetic field that modifies the magnetization of the heterostructure from a ground magnetic state that is layered antiferromagnetic.
1. A system for controlling electric current across a magnetic tunnel junction, the system comprising a layered heterostructure that includes:
a magnetic tunnel barrier comprising a layered magnet structure having a plurality of magnetic layers, including a first magnetic layer with a first magnetic vector and a second magnetic layer with a second magnetic vector that is opposite to the first magnetic vector, wherein both the first magnetic layer and the second magnetic layer comprise crystalline chromium triiodide having a unit-cell formula CrI 3 ;
a first electrode that is not magnetic and is electrically connected to the first magnetic layer; and
a second electrode that is not magnetic and is electrically connected to the second magnetic layer;
wherein the magnetic tunnel barrier permits significantly larger tunneling current to tunnel from the first electrode to the second electrode only when the first magnetic vector and the second magnetic vector are aligned.
2. The system of claim 1 , wherein the first magnetic layer and the second magnetic layer of the layered heterostructure are bonded together by van der Waals forces.
3. The system of claim 1 , wherein the layered heterostructure further includes at least one additional magnetic layer, which is bonded by van der Waals forces.
4. The system of claim 3 , wherein the layered heterostructure has a total of three or four magnetic layers, and a magnetic spin vector of each magnetic layer is opposite its adjacent layers at ground state.
5. The system of claim 1 , wherein the layered heterostructure exhibits multiple intermediate tunneling magnetoresistance states in proportion to the number of magnetic layers.
6. The system of claim 1 , wherein the layered heterostructure is characterized by a tunneling magnetoresistance in the range of 310% to 57,000%.
7. The system of claim 1 , wherein the first electrode or the second electrode, or both, comprise graphene or graphite.
8. The system of claim 1 , further comprising a magnet configured to apply a magnetic field to the layered heterostructure sufficient to modulate the magnetizations of the magnetic layers.
9. The system of claim 8 , wherein the magnet is configured to apply a magnetic field normal to an in-plane direction of the layered heterostructure.
10. The system of claim 8 , wherein the magnet is configured to apply a magnetic field parallel to an in-plane direction of the layered heterostructure.
11. The system of claim 8 , wherein the external applied magnetic field is characterized by a field strength in the range of 0 to 9 Tesla.
12. The system of claim 1 , further comprising a temperature control system configured to cool the system below a critical temperature of the crystalline chromium triiodide.
13. The system of claim 1 , further comprising a voltage source electrically coupled to the first electrode and the second electrode, and configured to apply an electric field to the layered heterostructure sufficient to modify the magnetizations of the magnetic layers.
14. A method of controlling an electric current across a magnetic tunnel barrier in a system according to claim 1 , the layered heterostructure of the magnetic tunnel barrier having a characteristic magnetic structure, the method comprising:
applying a voltage to the layered heterostructure of the magnetic tunnel barrier, between the first electrode and the second electrode;
applying a magnetic field to the layered heterostructure; and
modulating the magnetic field to control an electric current flowing from the first electrode to the second electrode.
15. The method of claim 14 , further comprising cooling the layered heterostructure to a temperature below the critical temperature of the crystalline chromium triiodide.
16. The method of claim 14 , further comprising aligning the magnetic field either normal to or parallel to the in-plane direction of the layered heterostructure.
17. The method of claim 14 , further comprising modulating the voltage to control the electric current flowing between the first electrode and the second electrode.
18. The method of claim 14 , further comprising repeatedly modulating the magnetic field to toggle the layered heterostructure between a relatively insulating state and a conducting state.
19. The method of claim 18 , wherein the layered heterostructure exhibits multiple intermediate magnetic states, and wherein the method further comprises modulating the magnetic field and applied voltage to select for one of the multiple intermediate magnetic states.
20. The method of claim 14 , wherein applying the magnetic field to the layered heterostructure comprises applying a magnetic field in the range of 0.1 to 9 Tesla.