Jeffrey Bokor, David Bryan Carlton and Nathan Emley
NRI and National Science Foundation
Nano-scale magnetic islands, or nanomagnets, may interact with one another via their short-ranged magnetostatic dipole fields provided their separation is sufficiently small. Due to the small magnetic moment of each island, these dipole fields can strongly affect the orientation of neighboring nanomagnets. In such a paradigm the nanomagnets are patterned into an elliptical or rectangular shape from epitaxial magnetic films, giving them uniform magnetization, and uniaxial shape anisotropy with the long dimension as the magnetically easy axis.
The 3-input majority logic gate (MLG) introduced by Imre et al.  is the current state-of-the-art for nanomagnet-based architecture. One problem with this approach is that if the inputs from the "magnetic wires" do not arrive at the same time the gate cannot be made to behave predictably.
We have developed a 2-input universal gate that does not suffer from race conditions and is scalable to arbitrary complexities. This creates the potential for an entirely nanomagnetic logic-based CPU.
Figure 1: Nanomagnetic islands and equivalent circuit
- A. Imre, G. Csaba, L. Ji, A. Orlov, G. H. Bernstein, and W. Porod, Science, Vol. 311, 2006, p. 205.