Magnetic switching component suitable for spintronics

Researchers from the University of Tokyo have created an electronic component that demonstrates functions and abilities important to future generations of computational logic and memory devices. Described in the journal Nature Communications, it is between one and two orders of magnitude more power efficient than previous attempts to create a component with the same kind of behaviour, which could help it realise developments in the emerging field of spintronics.

Spintronics explores the possibility of high-performance, low-power components for logic and memory. It’s based around the idea of encoding information into the spin — a property related to angular momentum — of an electron, rather than by using packets of electrons to represent logical bits, 1s and 0s.

One of the keys to unlock the potential of spintronics lies in the ability to quickly and efficiently magnetise materials. Professor Masaaki Tanaka and colleagues have made an important breakthrough in this area, creating a component — a thin film of ferromagnetic material — the magnetisation of which can be fully reversed with the application of very small current densities. These are between one and two orders of magnitude smaller than current densities required by previous techniques, so this device is far more efficient.

“We are trying to solve the problem of the large power consumption required for magnetisation reversal in magnetic memory devices,” said Prof Tanaka. “Our ferromagnetic semiconductor material — gallium manganese arsenide (GaMnAs) — is ideal for this task as it is a high-quality single crystal. Less ordered films have an undesirable tendency to flip electron spins. This is akin to resistance in electronic materials and it’s the kind of inefficiency we try to reduce.”

The GaMnAs film the team used for their experiment is special in another way too — it is especially thin thanks to a fabrication process known as molecular beam epitaxy. With this method, devices can be constructed more simply than other analogous experiments, which try and use multiple layers rather than single-layer thin films.

“We did not expect that the magnetisation can be reversed in this material with such a low current density; we were very surprised when we found this phenomenon,” said Prof Tanaka. “Our study will promote research of material development for more efficient magnetisation reversal. And this in turn will help researchers realise promising developments in spintronics.”

Image caption: This diagram shows how magnetisation reverses in a GaMnAs crystal. Image© 2019 Tanaka-Ohya Laboratory.

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