Templating layers for perpendicularly magnetized heusler films
Devices are described that include a multi-layered structure that is non-magnetic at room temperature, and which comprises alternating layers of Co and at least one other element E (such as Ga, Ge, and Sn). The composition of this structure is represented by Co 1-x E x , with x being in the range from 0.45 to 0.55. The structure is in contact with a first magnetic layer that includes a Heusler compound. An MRAM element may be formed by overlying, in turn, the first magnetic layer with a tunnel barrier, and the tunnel barrier with a second magnetic layer (whose magnetic moment is switchable). Improved performance of the MRAM element may be obtained by placing a pinning layer between the first magnetic layer and the tunnel barrier.
1. A device, comprising:
a multi-layered structure that is non-magnetic at room temperature, the structure comprising alternating layers of Co and at least one other element E selected from the group consisting of Ga, Ge, and Sn, wherein the composition of the structure is represented by Co 1-x E x , with x being in the range from 0.45 to 0.55; and
a first magnetic layer that includes a Heusler compound, the magnetic layer being in contact with the structure.
2. The device of claim 1 , wherein the magnetic moment of the magnetic layer is substantially perpendicular to the interface between the structure and the magnetic layer.
3. The device of claim 2 , wherein the magnetic layer has a thickness of less than 5 nm.
4. The device of claim 2 , wherein the magnetic layer has a thickness of less than 3 nm.
5. The device of claim 2 , wherein the magnetic layer has a thickness of one unit cell.
6. The device of claim 1 , wherein the Heusler compound is selected from the group consisting of Mn 3.1-z Ge, Mn 3.1-z Sn, and Mn 3.1-z Sb, with z being in the range from 0 to 1.1.
7. The device of claim 1 , wherein the Heusler compound is a ternary Heusler.
8. The device of claim 7 , wherein the ternary Heusler is Mn 3.1-z Co 1.1-y Sn, wherein z≤1.2 and y≤1.0.
9. The device of claim 1 , wherein E is Ga.
10. The device of claim 1 , wherein E is Ge.
11. The device of claim 1 , wherein E is Sn.
12. The device of claim 1 , comprising a substrate underlying the multi-layered structure.
13. The device of claim 12 , comprising a tunnel barrier overlying the first magnetic layer, thereby permitting current to pass through both the tunnel barrier and the first magnetic layer.
14. The device of claim 13 , comprising a second magnetic layer in contact with the tunnel barrier.
15. The device of claim 14 , wherein the tunnel barrier is MgO.
16. A device, comprising:
a substrate;
a multi-layered structure that is non-magnetic at room temperature, the structure comprising alternating layers of Co and at least one other element E selected from the group consisting of Ga, Ge, and Sn, wherein the composition of the structure is represented by Co 1-x E x , with x being in the range from 0.45 to 0.55, wherein the structure overlies the substrate;
a first magnetic layer that includes a Heusler compound, the magnetic layer being in contact with the structure;
a tunnel barrier overlying the first magnetic layer; and
a second magnetic layer in contact with the tunnel barrier, wherein the second magnetic layer has a magnetic moment that is switchable.
17. The device of claim 16 , comprising a capping layer in contact with the second magnetic layer.
18. The device of claim 16 , wherein the first magnetic layer includes Mn and an element selected from the group consisting of Sn, Sb, and Ge.
19. The device of claim 18 , wherein the first magnetic layer further includes Co.
20. A method, comprising:
using the device of claim 14 as a memory element.
21. A method, comprising:
using the device of claim 12 as part of a racetrack memory device.
22. A method of forming the device of claim 1 , comprising:
depositing Co and Ge, thereby forming a composite layer on a substrate;
annealing the composite layer, so that at least one layer of Co and at least one layer of Ge are formed from the composite layer, thereby forming the multi-layered structure; and
depositing the magnetic layer over the multi-layered structure.
23. The method of claim 22 , wherein the annealing takes place at a temperature of at least 400° C., and the element E includes Ga.
24. The method of claim 22 , wherein the annealing takes place at a temperature of at least 400° C., and the element E includes Ge.
25. The method of claim 22 , wherein the annealing takes place at a temperature less than 400° C., and the element E includes Sn.
26. The method of claim 22 , wherein the substrate is MgO.
27. The method of claim 26 , wherein a layer of Cr overlies the MgO.