Tunable tetragonal ferrimagnetic heusler compound with PMA and high TMR

1. A device, comprising:

a Heusler compound of the form Mn 3-x Co x Ge, wherein 0<x≤1, wherein Co accounts for at least 0.4 atomic percent of the Heusler compound and the Heusler compound has a tetragonal structure; and

a substrate oriented in the direction (001) and of the form YMn 1+d , wherein Y includes an element selected from the group consisting of Ir and Pt, and 0≤d≤4,

wherein the Heusler compound and the substrate are in proximity with each other, thereby allowing spin-polarized current to pass from one through the other.

2. The device of claim 1 , wherein Y is Ir.

3. The device of claim 1 , further comprising a tunnel barrier in contact with the Heusler compound.

4. The device of claim 3 , wherein the tunnel barrier includes Mg and O.

5. The device of claim 1 , further comprising a TaN layer between and in contact with the Heusler compound and the substrate.

6. The device of claim 1 , wherein the Heusler compound is of the form Mn 3-x Co x Ge, wherein 0<x≤1, and the substrate is of the form IrMn 3 .

7. The device of claim 1 , wherein the Heusler compound has a magnetic moment that is substantially perpendicular to the film plane.

8. The device of claim 7 , wherein the Heusler compound has a thickness of at least 10 Angstroms and not more than 500 angstroms.

9. The device of claim 1 , wherein a TaN layer is underneath and in contact with the substrate.

10. The device of claim 1 , wherein the Heusler compound has a thickness of less than 5 nm.

11. The device of claim 1 , wherein the Heusler compound has a thickness of less than 3 nm.

12. A device, comprising:

a Heusler compound of the form Mn 3-x Co x Ge, wherein 0<x≤1, wherein Co accounts for at least 0.4 atomic percent of the Heusler compound, the Heusler compound having a tetragonal structure;

a multi-layered structure that is non-magnetic at room temperature, the multi-layered structure comprising alternating layers of Co and E, wherein E comprises at least one other element that includes Al, wherein the composition of the structure is represented by Co 1-y E y , with y being in the range from 0.45 to 0.55; and

a substrate underlying the multi-layered structure;

wherein the Heusler compound and the multi-layered structure are in proximity with each other, thereby allowing spin-polarized current to pass from one through the other.

13. The device of claim 12 , wherein the magnetic moment of the Heusler compound is substantially perpendicular to the interface between the multi-layered structure and the Heusler compound.

14. The device of claim 12 , wherein the Heusler compound has a thickness of less than 5 nm.

15. The device of claim 12 , wherein the Heusler compound has a thickness of less than 3 nm.

16. The device of claim 12 , further comprising:

a tunnel barrier overlying the Heusler compound, thereby permitting current to pass through both the tunnel barrier and the Heusler compound.

17. The device of claim 16 , wherein the tunnel barrier includes Mg and O.

18. The device of claim 16 , further comprising a magnetic layer in contact with the tunnel barrier.

19. A device, comprising:

a Heusler compound of the form Mn 3-x Co x Ge, wherein 0<x≤1, wherein Co accounts for at least 0.4 atomic percent of the Heusler compound, the Heusler compound having a tetragonal structure;

a multi-layered structure that is non-magnetic at room temperature, the multi-layered structure comprising alternating layers of Co and E, wherein E comprises at least one other element that includes Al, wherein the composition of the structure is represented by Co 1-y E y , with y being in the range from 0.45 to 0.55; and

a substrate underlying the multi-layered structure;

wherein the Heusler compound and the multi-layered structure are in proximity with each other, thereby allowing spin-polarized current to pass from one through the other; and

wherein the Heusler compound has a thickness of one unit cell.

20. A device, comprising:

a Heusler compound of the form Mn 3-x Co x Ge, wherein 0<x≤1, wherein Co accounts for at least 0.4 atomic percent of the Heusler compound, the Heusler compound having a tetragonal structure;

a multi-layered structure that is non-magnetic at room temperature, the multi-layered structure comprising alternating layers of Co and E, wherein E comprises at least one other element that includes Al, wherein the composition of the structure is represented by Co 1-y E y , with y being in the range from 0.45 to 0.55; and

a substrate underlying the multi-layered structure;

wherein the Heusler compound and the multi-layered structure are in proximity with each other, thereby allowing spin-polarized current to pass from one through the other; and

wherein E is an AlGe alloy.

21. A device, comprising:

a Heusler compound of the form Mn 3-x Co x Ge, wherein 0<x≤1, wherein Co accounts for at least 0.4 atomic percent of the Heusler compound, the Heusler compound having a tetragonal structure;

a multi-layered structure that is non-magnetic at room temperature, the multi-layered structure comprising alternating layers of Co and E, wherein E comprises at least one other element that includes Al, wherein the composition of the structure is represented by Co 1-y E y , with y being in the range from 0.45 to 0.55; and

a substrate underlying the multi-layered structure;

wherein the Heusler compound and the multi-layered structure are in proximity with each other, thereby allowing spin-polarized current to pass from one through the other; and

wherein E is an AlGa alloy.

22. A device, comprising:

a Heusler compound of the form Mn 3-x Co x Ge, wherein 0<x≤1, wherein Co accounts for at least 0.4 atomic percent of the Heusler compound, the Heusler compound having a tetragonal structure;

a multi-layered structure that is non-magnetic at room temperature, the multi-layered structure comprising alternating layers of Co and E, wherein E comprises at least one other element that includes Al, wherein the composition of the structure is represented by Co 1-y E y , with y being in the range from 0.45 to 0.55; and

a substrate underlying the multi-layered structure;

wherein the Heusler compound and the multi-layered structure are in proximity with each other, thereby allowing spin-polarized current to pass from one through the other; and

wherein E includes an alloy selected from the group consisting of AlSn, AlGe, AlGaGe, AlGaSn, AlGeSn, and AlGaGeSn.

23. A method, comprising:

using a device as a memory element, the device including

a Heusler compound of the form Mn 3-x Co x Ge, wherein 0<x≤1, wherein Co accounts for at least 0.4 atomic percent of the Heusler compound, the Heusler compound having a tetragonal structure; and

a substrate oriented in the direction (001) and of the form YMn 1+d , wherein Y includes an element selected from the group consisting of Ir and Pt, and 0<d≤4;

wherein the Heusler compound and the substrate are in proximity with each other, thereby allowing spin-polarized current to pass from one through the other and

wherein a TaN layer is underneath and in contact with the substrate.

24. A method comprising:

using a device as a memory element, the device including

a first magnetic layer that includes a Heusler compound of the form Mn 3-x Co x Ge, wherein 0<x≤1, wherein Co accounts for at least 0.4 atomic percent of the tetragonal Heusler compound, the Heusler compound having a tetragonal structure; and

a multi-layered structure that is non-magnetic at room temperature, the structure comprising alternating layers of Co and E, wherein E comprises at least one other element that includes Al, wherein the composition of the structure is represented by Co 1-y E y , with y being in the range from 0.45 to 0.55; and

a tunnel barrier;

a second magnetic layer; wherein the first magnetic layer, the multi-layered structure, the tunnel barrier, and the second magnetic layer are in proximity with each other, thereby allowing spin-polarized current to pass from one through the other;

wherein the tunnel barrier includes MgO.

25. A device, comprising:

a substrate;

a underlayer oriented in the direction (001) that is non-magnetic at room temperature, the underlayer overlying the substrate;

a first magnetic layer that includes a Heusler compound Mn 3-x Co x Ge, wherein 0<x≤1, the first magnetic layer being in contact with the underlayer, wherein the magnetic moment of the first layer is switchable;

a tunnel barrier overlying the first magnetic layer; and

a second magnetic layer in contact with the tunnel barrier.

26. The device of claim 25 , further comprising a capping layer in contact with the second magnetic layer.

27. The device of claim 25 , wherein the magnetic moment of the first magnetic layer is substantially perpendicular to the interface between the tunnel barrier and the first magnetic layer.