Researchers have developed a technology that could enable extreme miniaturization of computer components, paving the way for compact and powerful devices.
The smaller the transistors and logic gates in a processor, the more processing power can be packed into a smaller area. But the physical limitations of silicon mean that we are reaching the limits of how small these components can be.
However, a new technique that uses ultrafast switching between spin states in 2D magnets – to represent switching between the binary states 1 and 0 – can lead to significantly denser and more energy-efficient components.
This technique is made possible by a new type of magnetic tunnel junction (MTJ) – a material structure that acts as a data storage device in a computer system. The scientists inserted chromium triiodide (a two-dimensional insulating magnet) between graphene layers and passed an electric current through it to determine the orientation of the magnet within each chromium triiodide layer.
Using these MTJs could mean packing more computing power into a chip than previously thought possible – while using significantly less energy during the switching process. The researchers published their results in a new study published on May 1 in the journal Nature communication.
In the paper, the scientists showed that 2D magnets can be polarized to represent binary states – the ones and zeros of computer data – paving the way for highly energy-efficient computers.
Using spintronics for faster computing
Precisely controlling the magnetic phase of 2D materials is a crucial step in spintronics (controlling the spin of an electron and its associated magnetic moment). By precisely controlling the current, the new technique can change the spin states in chromium triiodide using the polarity and amplitude of the current. This is possible because the compound is ferromagnetic (it is magnetic and can attract magnets in a similar way to iron). This compound is also a semiconductor – a material whose conductivity lies between that of a metal and that of an insulator.
A key component for spintronics is the MTJ – two ferromagnetic layers separated by an insulating barrier. Controlling the spin state of an MTJ is a technique already used in various computer components, such as the read heads of hard drives. However, precisely controlling the thickness of each layer and the quality of their interfaces with each other has proven difficult.
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The materials must be able to withstand high current densities of at least 10 million amps across an area roughly the size of a fingernail – while also meeting the requirements for miniaturization and energy efficiency of the devices. For comparison: a typical lightning bolt has 1,000 to 300,000 amps.
“This paper is about the fact that there are two possible states of tunneling current: spin-parallel and antiparallel.” Adelina Iliea physics lecturer at the University of Bath in the UK who specializes in 2D magnets, told LiveScience. “If there are two defined states, they can be used as logic gates in a computer.”
Significantly higher energy efficiency for future AI systems
The scientists developed the two-dimensional van der Waals magnets (chromium triiodide) and then layered atomically thin flakes of graphene, hexagonal boron nitride and chromium triiodide on top of each other to form tunnel junction elements. They cooled these to near absolute zeroAt the same time, they passed an electric current through the material and measured it with a source meter at 16-millisecond intervals.
They found that the voltage switched randomly between levels corresponding to the spin-parallel and spin-antiparallel states within chromium triiodide, with the switching direction determined by the polarity and amplitude of the current. The duration for each magnetic state was typically 10 milliseconds, while the switching time between the two states was on the order of microseconds (a microsecond is a millionth of a second).
“These states are not really stable,” Ilie explained. “What actually happens is that the current stochastically switches from one state to the other, back and forth, but the average time it stays more or less in one state or the other depending on the voltage. This gives us two states that we can choose deterministically.”
The two states that can be used as logic gates allow operation on a much smaller scale than was previously possible. This technology could allow manufacturers to create computer chips with greater processing power. However, because operating temperatures close to absolute zero are required, the practical implementation of futuristic devices would be challenging.
“What makes this kind of work different is that the energy needed to go from one state to another appears to be an order of magnitude less than traditional magnetic tunnel junctions,” Ilie concluded. “With new technologies like generative AI increasing power consumption enormously, it’s not going to be possible to keep up, so you need devices that are energy efficient.”
