A class of non-volatile memory devices, called MRAM, based on quantum magnetic materials, can offer performance thousands of times higher than current next-generation memory devices. Materials known as antiferromagnets were previously shown to store stable memory states, but they were difficult to read. This new study paves the way for an efficient way to read memory states, with the potential to do it incredibly fast, too.
You can probably blink about four times a second. You could say that this blink frequency is 4 hertz (cycles per second). Imagine trying to blink a billion times per second, or at 1 gigahertz, it would be physically impossible for a human. But this is the current order of magnitude in which contemporary high-end digital devices, such as magnetic memory, change states as operations are performed. And many people want to push the limit a thousand times further, to the rate of a trillion times per second, or terahertz.
The barrier to the realization of faster memory devices may be the materials used. Not yet common enough to appear in your home computer, today’s high-speed MRAM chips use typical magnetic or ferromagnetic materials. These are read using a technique called tunneling magnetoresistance. This requires that the magnetic components of the ferromagnetic material be aligned in parallel arrangements. However, this arrangement creates a strong magnetic field that limits the speed at which memory can be read from or written to.
“We have achieved an experimental breakthrough that overcomes this limitation, and it is thanks to a different type of material, antiferromagnets,” said Professor Satoru Nakatsuji of the Department of Physics at the University of Tokyo. “Antiferromagnets differ from typical magnets in many ways, but in particular, we can arrange them in ways other than parallel lines. This means we can negate the magnetic field that would result from parallel arrangements. It is believed that the magnetization of ferromagnets “it is necessary for tunneling the magnetoresistance to read from memory. Surprisingly, however, we found that it is also possible for a special class of antiferromagnets without magnetization, and hopefully it can work at very high speeds.”
Nakatsuji and his team believe that rates of change in the terahertz range can be achieved, and that this is also possible at room temperature, whereas previous attempts required much cooler temperatures and did not yield as promising results. However, to improve their idea, the team needs to refine their devices, and improving the way they build them is key.
“Although the atomic components of our materials are quite familiar (manganese, magnesium, tin, oxygen, etc.), the way we combine them to form a usable memory component is novel and unknown,” said researcher Xianzhe Chen. “We grow crystals in a vacuum, in incredibly thin layers using two processes called molecular beam epitaxy and magnetron sputtering. The higher the vacuum, the purer the samples we can grow. It’s an extremely challenging procedure, and if we improve it , we will make our lives easier and produce more effective devices as well.”
These antiferromagnetic memory devices exploit a quantum phenomenon known as entanglement, or distance interaction. But despite this, this research is not directly related to the increasingly famous field of quantum computing. However, the researchers suggest that developments like this could be useful or even essential in building a bridge between the current paradigm of electronic computing and the emerging field of quantum computers.