The new approach is based on magnetic random access memory (MRAM) elements that contain two magnetic layers separated by a spacer. If the magnetic moments of the two layers are parallel, the electrical resistance of the element is low and this is taken to represent a ‘1’; the antiparallel, high-resistance state is taken to represent a ‘0’. The magnetic moments of the layers can be flipped by passing an electric current through an input line to produce a magnetic field.

The device proposed by Ney and co-workers is based on a single element that has two independent input lines (called A and B: see figure 1). This means that four initial states are possible altogether. These are ‘00’, ‘01’, ‘10’ and ‘11’, where ‘00’ represents a negative current passing through both input lines, ‘01’ is a negative current through A and a positive current through B, and so on. Ney and colleagues show that this set-up is enough to provide storage and the AND and OR operations. And by adding a third input line, they can also reproduce the NAND and NOR operations.

The researchers say that their device has many advantages over transistor-based logic and that it could lead to programmable magneto-logic circuits in the near future. “Since our concept is quite straightforward and is based on existing technology, the fabrication of a reprogrammable magneto-logic circuit is foreseeable in the near future,” said Ney. “Our work is still only a concept, but we intend to make a practical, working device using these ideas.”