A class of non-volatile memory devices called MRAM, based on quantum magnetic materials, can offer performance thousands of times beyond the current state of the art. The materials known as antiferromagnets were previously shown to store stable memory states but were difficult to read. This new study paves the way for an efficient way to read memory states, with the potential to do so incredibly quickly, too.
You can probably blink about four times a second. You could say this flashing frequency is 4 hertz (cycles per second). Imagine trying to blink 1 billion times per second or at 1 gigahertz, it would be physically impossible for a human. However, this is the current magnitude at which modern high-end digital devices, such as magnetic storage, change states as operations are performed. And many people want to push the limit a thousand times further, into the regime of a trillion times per second, or terahertz.
The barrier to realizing faster storage devices can be the materials used. Current high-speed MRAM chips, which are not yet common enough to show up in your home computer, use typically magnetic or ferromagnetic materials. These are read using a technique called tunneling magnetoresistance. To do this, the magnetic components of the ferromagnetic material must be arranged in parallel. However, this arrangement creates a strong magnetic field that limits the speed at which the memory can be read or written.
‘We have made an experimental breakthrough that overcomes this limitation thanks to a different type of material, antiferromagnets,’ said Professor Satoru Nakatsuji from the University of Tokyo’s Department of Physics. “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 is necessary for tunneling magnetoresistance to read from memory. Amazingly, however, we have found that this is also possible for a special class of antiferromagnets without magnetization, and hopefully can operate at very high speeds.
Nakatsuji and his team believe switching speeds in the terahertz range are achievable, even at room temperature, while previous attempts required much colder temperatures and yielded less promising results. To improve their idea, however, the team needs to refine their devices, and improving the way they make them is key.
“Although the atomic components of our materials are fairly familiar — manganese, magnesium, tin, oxygen, and so on — the way we combine them to form a viable storage component is new and unfamiliar,” said researcher Xianzhe Chen. “We grow crystals in vacuum in incredibly fine layers using two processes called molecular beam epitaxy and magnetron sputtering. The higher the vacuum, the purer the samples we can grow. It is an extremely challenging process and if we improve it, we will make our lives easier and also produce more effective devices.”
These antiferromagnetic memory devices exploit a quantum phenomenon known as entanglement, or action at a distance. Nevertheless, this research is not directly related to the increasingly well-known field of quantum computing. However, researchers suggest that developments such as these could be useful or even essential in bridging the current paradigm of electronic computing and the emerging field of quantum computing.