Amorphous spin diffusion layer for modified double magnetic tunnel junction structure
View Patent ↗A modified double magnetic tunnel junction structure is provided which includes an amorphous spin diffusion layer (i.e., an amorphous non-magnetic, spin-conducting metallic layer) sandwiched between a magnetic free layer and a first tunnel barrier layer; the first tunnel barrier layer contacts a first magnetic reference layer. A second tunnel barrier layer is located on the magnetic free layer and a second magnetic reference layer is located on the second tunnel barrier layer. Such a modified double magnetic tunnel junction structure exhibits efficient switching (at a low current) and speedy readout (high tunnel magnetoresistance).
1. A modified double magnetic tunnel junction (mDMTJ) structure comprising:
a first magnetic reference layer;
a first tunnel barrier layer having a first surface contacting a surface of the first magnetic reference layer;
an amorphous non-magnetic, spin-conducting metallic layer having a first surface contacting a second surface of the first tunnel barrier layer which is opposite the first surface of the first tunnel barrier layer, wherein the amorphous non-magnetic, spin-conducting metallic layer is composed of a spin-conserving metallic material including a metal having an atomic number of equal to, or less than, 30;
a magnetic free layer having a first surface contacting a second surface of the amorphous non-magnetic, spin-conducting metallic layer which is opposite the first surface of the amorphous non-magnetic, spin-conducting metallic layer;
a second tunnel barrier layer having a first surface contacting a second surface of the magnetic free layer which is opposite the first surface of the magnetic free layer; and
a second magnetic reference layer having a first surface contacting a second surface of the second tunnel barrier layer which is opposite the first surface of the second tunnel barrier layer.
2. The mDMTJ structure of claim 1 , wherein the amorphous non-magnetic, spin-conducting metallic layer is composed of an A-B alloy wherein A is one of magnesium (Mg), aluminum (Al), silicon (Si), titanium (Ti), vanadium (V), copper (Cu), or zinc (Zn), and B is one of beryllium (Be), boron (B), carbon (C) or nitrogen (N).
3. The mDMTJ structure of claim 1 , wherein the first magnetic reference layer is located at a bottom portion of the mDMTJ structure, and the second magnetic reference layer is located at a top portion of the mDMTJ structure.
4. The mDMTJ structure of claim 3 , wherein at least one of the first magnetic reference layer and the second magnetic reference layer comprises a lower magnetic reference layer, an anti-ferromagnetic coupling layer, and an upper magnetic reference layer.
5. The mDMTJ structure of claim 3 , wherein the first tunnel barrier layer and the second tunnel barrier layer have a same lateral dimension.
6. The mDMTJ structure of claim 3 , wherein the first tunnel barrier layer has a first lateral dimension, and the second tunnel barrier layer has a second lateral dimension that is less than the first lateral dimension.
7. The mDMTJ structure of claim 6 , wherein the magnetic free layer is located on a pedestal portion of the amorphous non-magnetic, spin-conducting metallic layer, the pedestal portion of the amorphous non-magnetic, spin-conducting metallic layer has the second lateral dimension, and a remaining portion of the amorphous non-magnetic, spin-conducting metallic layer has the first lateral dimension.
8. The mDMTJ structure of claim 1 , wherein the second magnetic reference layer is located at a bottom portion of the mDMTJ structure, and the first magnetic reference layer is located at a top portion of the mDMTJ structure.
9. The mDMTJ structure of claim 8 , wherein at least one of the first magnetic reference layer and the second magnetic reference layer comprises a lower magnetic reference layer, an anti-ferromagnetic coupling layer, and an upper magnetic reference layer.
10. The mDMTJ structure of claim 8 , wherein the first tunnel barrier layer and the second tunnel barrier layer have a same lateral dimension.
11. The mDMTJ structure of claim 8 , wherein the first tunnel barrier layer has a first lateral dimension, and the second tunnel barrier layer has a second lateral dimension that is less than the first lateral dimension.
12. The mDMTJ structure of claim 11 , wherein the magnetic free layer contacts a lower portion of the amorphous non-magnetic, spin-conducting metallic layer, the lower portion of the amorphous non-magnetic, spin-conducting metallic layer has the second lateral dimension, and an upper portion of the amorphous non-magnetic, spin-conducting metallic layer has the lateral first dimension.
13. A spin-transfer torque (STT) magnetic tunnel junction (MTJ) memory element comprising:
a modified double magnetic tunnel junction (mDMTJ) structure sandwiched between a first electrode and a second electrode, wherein the mDMTJ structure comprises a first magnetic reference layer, a first tunnel barrier layer having a first surface contacting a surface of the first magnetic reference layer, an amorphous non-magnetic, spin-conducting metallic layer having a first surface contacting a second surface of the first tunnel barrier layer which is opposite the first surface of the first tunnel barrier layer, a magnetic free layer having a first surface contacting a second surface of the amorphous non-magnetic, spin-conducting metallic layer which is opposite the first surface of the amorphous non-magnetic, spin-conducting metallic layer, a second tunnel barrier layer having a first surface contacting a second surface of the magnetic free layer which is opposite the first surface of the magnetic free layer, and a second magnetic reference layer having a first surface contacting a second surface of the second tunnel barrier layer which is opposite the first surface of the second tunnel barrier layer, wherein the amorphous non-magnetic, spin-conducting metallic layer is composed of a spin-conserving metallic material including a metal having an atomic number of equal to, or less than, 30.
14. The STT MTJ memory element of claim 13 , wherein the amorphous non-magnetic, spin-conducting metallic layer is composed of an A-B alloy wherein A is one of magnesium (Mg), aluminum (Al), silicon (Si), titanium (Ti), vanadium (V), copper (Cu), or zinc (Zn), and B is one of beryllium (Be), boron (B), carbon (C) or nitrogen (N).
15. The STT MTJ memory element of claim 13 , wherein the first magnetic reference layer is located at a bottom portion of the mDMTJ structure, and the second magnetic reference layer is located at a top portion of the mDMTJ structure.
16. The STT MTJ memory element of claim 15 , wherein at least one of the first magnetic reference layer and the second magnetic reference layer comprises a lower magnetic reference layer, an anti-ferromagnetic coupling layer, and an upper magnetic reference layer.
17. The STT MTJ memory element of claim 15 , wherein the first tunnel barrier layer and the second tunnel barrier layer have a same lateral dimension.
18. The STT MTJ memory element of claim 15 , wherein the first tunnel barrier layer has a first lateral dimension, and the second tunnel barrier layer has a second lateral dimension that is less than the first lateral dimension.
19. The STT MTJ memory element of claim 18 , wherein the magnetic free layer is located on a pedestal portion of the amorphous non-magnetic, spin-conducting metallic layer, the pedestal portion of the amorphous non-magnetic, spin-conducting metallic layer has the second lateral dimension, and a remaining portion of the amorphous non-magnetic, spin-conducting metallic layer has the first lateral dimension.
20. The STT MTJ memory element of claim 13 , wherein the second magnetic reference layer is located at a bottom portion of the mDMTJ structure, and the first magnetic reference layer is located at a top portion of the mDMTJ structure.
21. The STT MTJ memory element of claim 20 , wherein at least one of the first magnetic reference layer and the second magnetic reference layer comprises a lower magnetic reference layer, an anti-ferromagnetic coupling layer, and an upper magnetic reference layer.
22. The STT MTJ memory element of claim 20 , wherein the first tunnel barrier layer and the second tunnel barrier layer have a same lateral dimension.
23. The STT MTJ memory element of claim 20 , wherein the first tunnel barrier layer has a first lateral dimension, and the second tunnel barrier layer has a second lateral dimension that is less than the first lateral dimension.
24. The STT MTJ memory element of claim 23 , wherein the magnetic free layer contacts a lower portion of the amorphous non-magnetic, spin-conducting metallic layer, the lower portion of the amorphous non-magnetic, spin-conducting metallic layer has the second lateral dimension, and an upper portion of the amorphous non-magnetic, spin-conducting metallic layer has the first lateral dimension.