With silicon-based processors facing some inexorable limits, scientists are looking elsewhere to keep computing on its exponential growth track. One potential alternative that is getting some traction is magnet-based computing. A group of electrical engineers at the Technische Universität München (TUM) is studying the feasibility of using miniature magnets as the building block for integrated circuits.
The group ran experiments using three-dimensional arrangements of nanometer-scale magnets instead of transistors. Their results are detailed in the journal Nanotechnology.
The 3D stack of nanomagnets function as a majority logic gate, which could act as a programmable switch in a digital circuit. The mechanism is a lot like ordinary bar magnets. When you bring them near each other, the opposite poles attract and like poles repel each other. If you bring together several bar magnets and hold all but one in a fixed position, 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 a similar way, with the reversal of polarity representing a switch between Boolean logic states, i.e., 1 and 0. In the 3D majority gate created by the research team, the state 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.
Nanomagnetic logic is one of the technologies being considered by the industry group, International Technology Roadmap for Semiconductors. Magnetic circuits are non-volatile, so they maintain state without power. They also have the benefit of extremely low energy consumption, operate at room temperature and resist radiation.
Perhaps most importantly, nanomagnetic logic can support very dense packing. The building blocks, the individual nanomagnets, are equivalent in size to individual transistors, but transistors require contacts and wiring, and nanomagnets operate purely with coupling fields.
The 3D design also works to make nanomagnetic logic competitive. TUM doctoral candidate Irina Eichwald, lead author of the Nanotechnology paper, explains: “The 3D majority gate demonstrates that magnetic computing can be exploited in all three dimensions, in order to realize monolithic, sequentially stacked magnetic circuits promising better scalability and improved packing density.”
“It is a big challenge to compete with silicon CMOS circuits,” adds Dr. Markus Becherer, leader of the TUM research group within the Institute for Technical Electronics. “However, there might be applications where the non-volatile, ultralow-power operation and high integration density offered by 3D nanomagnetic circuits give them an edge.”