Could low-power 3D nanomagnetic logic replace transistors?

October 01, 2014 // By Paul Buckley
Electrical engineers at the Technische Universität München (TUM) have demonstrated a new kind of building block for digital integrated circuits that require extremely low energy consumption.

Future computer chips could be based on three-dimensional arrangements of nanometer-scale magnets instead of transistors.

As the main enabling technology of the semiconductor industry – CMOS fabrication of silicon chips – approaches fundamental limits, the TUM researchers and collaborators at the University of Notre Dame are exploring 'magnetic computing' as an alternative and have reported their latest results in the journal Nanotechnology.

In a 3D stack of nanomagnets, the researchers have implemented a so-called majority logic gate, which could serve as a programmable switch in a digital circuit. They explain the underlying principle with a simple illustration: Think of the way ordinary bar magnets behave when you bring them near each other, with opposite poles attracting and like poles repelling each other. Now imagine bringing several bar magnets together and holding all but one in a fixed position. Their magnetic fields can be thought of as being coupled into one, and the 'north-south' polarity of the magnet that is free to flip will be determined by the orientation of the majority of fixed magnets.

Gates made from field-coupled nanomagnets work in an analogous way, with the reversal of polarity representing a switch between Boolean logic states, the binary digits 1 and 0. In the 3D majority gate reported by the TUM-Notre Dame team, the state of the device is determined by three input magnets, one of which sits 60 nanometers below the other two, and is read out by a single output magnet.

The work builds on capabilities the collaborators have developed over several years, ranging from simulations of magnetic behavior to innovative fabrication and measuring techniques.

The researchers reported the world's first 'domain wall gate' at last year's International Electron Devices Meeting. The scientists use focused ion-beam irradation to change the magnetic properties of sharply defined spots on the device. So-called domain walls generated there are able to flow through magnetic wires under the control of surrounding nanomagnets. The