Heavy metal multilayers for switching of magnetic unit via electrical current without magnetic field, method and applications

1. An electric-current-controllable magnetic unit, comprising:

a substrate,

an electric-current channel disposed on the substrate, the electric-current channel comprising a composite heavy-metal multilayer comprising at least one heavy-metal,

wherein the composite heavy-metal multilayer comprises an alternating first layer and second layer,

wherein the first layer comprises a first heavy metal and the second layer comprises a second heavy metal that is different than the first heavy metal;

a capping layer disposed over the electric-current channel; and

at least one ferromagnetic layer disposed between the electric-current channel and the capping layer.

2. The electric-current-controllable magnetic unit of claim 1 , wherein the electric-current channel, the capping layer and the ferromagnetic layer are configured such that a magnetization direction thereof changes when an electric current is passed through the electric-current channel.

3. The electric-current-controllable magnetic unit of claim 1 , wherein the at least one heavy-metal comprises Pt, Pd, Au, Ag, Ru, Ir, Ta, W, Cr, Bi, Mo, Re, Os, Pb, Bi TI, combinations thereof, or alloys thereof.

4. The electric-current-controllable magnetic unit of claim 3 , wherein the alloys thereof comprise CuBi, AgBi, CuIr, Aglr, CuW, AgW, CuTa, AgTa, TaAl, Nb 3 Sn, W3Ge, TaN, WN, NbN or combinations thereof.

5. The electric-current-controllable magnetic unit of claim 1 , wherein the electric-current channel comprises a thickness in the range of from about 1.0 nm to less than about 8.0 nm.

6. The electric-current-controllable magnetic unit of claim 1 , wherein a ferromagnet of the at least one ferromagnetic layer comprises an in-plane magnetized ferromagnet, a perpendicular-magnetized ferromagnet, or both.

7. The electric-current-controllable magnetic unit of claim 6 , wherein the in-plane magnetized ferromagnet comprises Co, Fe, CoFeB, NiFe, CoFe, CoFeAl, CoMnSi, or any combination thereof.

8. The electric-current-controllable magnetic unit of claim 6 , wherein the perpendicular magnetized ferromagnet comprises Co, Fe, CoFeB, CoFeAl, CoMnSi; [Co/Pt] n , [Co/Pd] n , [Co/Ni] n , FePt, CoPt, FePd, TeFeCo, GdCo, MnGa, MnGe, MnSi, alloys thereof, or any combination thereof.

9. The electric-current-controllable magnetic unit of claim 1 , wherein the at least one ferromagnetic layer comprises an antiferromagnetic sub-structure comprising a first ferromagnet (FM-I), a second ferromagnet (FM-II) and a nonmagnetic material disposed between FM-I and FM-II.

10. The electric-current-controllable magnetic unit of claim 9 , wherein the nonmagnetic material comprises Ru, Cu, Cr or any combination thereof.

11. The electric-current-controllable magnetic unit of claim 1 , further comprising a magnetic tunnel junction comprising the at least one ferromagnetic layer and an insulating layer, wherein the at least one ferromagnetic layer comprises a first ferromagnetic layer and a second ferromagnetic layer, and wherein the insulating layer is disposed between the first insulating layer and the second insulating layer.

12. The electric-current-controllable magnetic unit of claim 11 , wherein the first ferromagnetic layer comprises a first magnetic coercive field, wherein the second ferromagnetic layer comprises a second magnetic coercive field, wherein the first and second magnetic coercive fields are alignable substantially parallel to each other in a first state of the magnetic tunnel junction and are alignable substantially antiparallel in a second state of the magnetic tunnel junction.

13. The electric-current-controllable magnetic unit of claim 12 , wherein the electric-current channel, the capping layer and the ferromagnetic layer are configured such that an electric-current of tunneling electrons through the insulating layer is greater in the first state than in the second state.

14. The electric-current-controllable magnetic unit of claim 11 , wherein the insulating layer comprises MgO, AlO, HfO 2 , Ta 2 O 5 , ZrO, or any combination thereof.

15. An electric-current-controllable magnetic unit, comprising:

a substrate,

an electric-current channel disposed on the substrate, the electric-current channel comprising a composite heavy-metal multilayer comprising at least one heavy-metal, wherein the at least one heavy-metal comprises a spin Hall angle;

at least one ferromagnetic layer disposed on the electric-current channel

a capping insulator layer disposed on the ferromagnetic layer; and

a top heavy-metal layer disposed on the capping insulator layer,

wherein the top heavy-metal layer comprises at least one layer of a heavy-metal that comprises a spin Hall angle of the same sign as that of the composite heavy-metal multilayer.

16. The electric-current-controllable magnetic unit of claim 15 , wherein the at least one heavy-metal comprises Pt, Pd, Au, Ag, Ru, Ir, Ta, W, Cr, Bi, Mo, Re, Os, Pb, Bi TI, combinations thereof, or alloys thereof.

17. A method of operating an electric-current-controllable magnetic unit, comprising

supplying an electric current to an electric-current-controllable magnetic unit, wherein the electric-current-controllable magnetic unit comprises:

a substrate,

an electric-current channel disposed on the substrate, the electric-current channel comprising a composite heavy-metal multilayer comprising at least one heavy-metal,

wherein the composite heavy-metal multilayer comprises an alternating first layer and second layer,

wherein the first layer comprises a first heavy metal and the second layer comprises a second heavy metal that is different than the first heavy metal;

a capping layer disposed over the electric-current channel; and

at least one ferromagnetic layer disposed between the electric-current channel and the capping layer; and

changing a magnetization direction of the electric-current-controllable magnetic unit,

wherein the electric current passes through the composite heavy-metal layer.

18. The method of claim 17 , wherein the electric-current-controllable magnetic unit comprises a magnetic tunnel junction comprising the at least one ferromagnetic layer and an insulating layer, wherein the at least one ferromagnetic layer comprises a first ferromagnetic layer and a second ferromagnetic layer, and wherein the insulating layer is disposed between the first ferromagnetic layer and the second ferromagnetic layer.

19. The method of claim 18 , wherein the first ferromagnetic layer comprises a first magnetic coercive field, wherein the second ferromagnetic layer comprises a second magnetic coercive field, and wherein the first and second magnetic coercive fields are alignable substantially parallel to each other in a first state of the magnetic tunnel junction and are alignable substantially antiparallel in a second state of the magnetic tunnel junction.

20. The method of claim 19 , wherein the method further comprises switching magnetization of the first ferromagnetic layer from one of the first and second states to the other of the first and second states.