Magnetic domain wall logic devices and interconnect

1. An apparatus comprising:

first, second, and third free magnetic layers;

a first metal layer of first material coupled to the first and third free magnetic layers; and

a second metal layer of second material different from the first material, the second metal layer coupled to the second and third free magnetic layers; and

a domain wall device coupled to the first or second free magnetic layers.

2. The apparatus of claim 1 further comprises a power supply contact coupled to the third free magnetic layer.

3. The apparatus of claim 2 further comprises a ground contact coupled to the second free magnetic layer.

4. The apparatus of claim 3 , wherein the power supply contact is coupled to a positive power supply to achieve a function of a repeater.

5. The apparatus of claim 3 , wherein the power supply contact is coupled to a negative power supply to achieve a function of an inverter.

6. The apparatus of claim 2 , wherein the first metal layer forms an input, and wherein the second metal layer forms an output.

7. The apparatus of claim 1 , wherein the first metal layer is composed of a transition metal from the platinum group of the periodic table.

8. The apparatus of claim 7 , wherein the transition metal from the platinum group of the periodic table is Ru.

9. The apparatus of claim 1 , wherein the second metal layer is composed of Cu.

10. The apparatus of claim 1 , wherein the third free magnetic layer is thicker than thicknesses of the first and second magnetic layers.

11. The apparatus of claim 1 , wherein the first and second metal layers are decoupled from one another.

12. An apparatus comprising:

first, second, and third free magnetic layers;

a first metal layer of first material coupled to the first and third free magnetic layers; and

a second metal layer of second material different from the first material, the second metal layer coupled to the second and third free magnetic layers;

a power supply contact coupled to the third free magnetic layer, wherein the first metal layer is coupled to a logic unit to provide a current pulse to cause a domain wall to propagate through the first metal layer.

13. A spin torque majority gate device comprising: a free magnetic layer configured in ring; and

first second, third, and fourth free magnetic layers coupled to the free magnetic layer, wherein the first and third free magnetic layers are substantially parallel to one another, wherein the second and fourth free magnetic layers are substantially parallel to one another such that the second and fourth free magnetic layers are substantially perpendicular to the first and third free magnetic layers.

14. The spin torque majority gate device of claim 13 , wherein each of the first, second, third, and fourth free magnetic layers comprises an apparatus comprising:

first, second, and third free magnetic layers;

a first metal layer of first material coupled to the first and third free magnetic layers; and

a second metal layer of second material different from the first material, the second metal layer coupled to the second and third free magnetic layers.

15. The spin torque majority gate device of claim 14 , wherein the free magnetic layer configured as a ring is coupled to the first, second, third, and fourth free magnetic layers via respective second metal layers.

16. A spin torque majority gate device comprising:

a free magnetic layer configured in ring; and

first, second, third, and fourth free magnetic layers coupled to the free magnetic layer, wherein the first, second, and fourth free magnetic layers to provide respective spin torques to the free magnetic layer, and wherein the third free magnetic layer to provide an output indicating a logic function according to respective spin directions in the first, second, and fourth free magnetic layers.

17. A spin torque majority gate device comprising:

a free magnetic layer configured in ring; and

first, second, third, and fourth free magnetic layers coupled to the free magnetic layer, wherein the first free magnetic layer to provide spin torque to the free magnetic layer, and wherein the second, third, and fourth free magnetic layers to provide respective outputs according to spin direction in the first free magnetic layer.