December 05, 2019 by Luke James
MIT researchers have developed a new circuit that offers a path to ‘spintronic’ devices that require little electricity and generate almost no heat using a nanometer-wide “magnetic domain wall”.
MIT researchers have designed a new innovative circuit design that relies on magnetic waves instead of electricity. This design may be a promising step forward in finally making magnetic-based devices, known as “spintronics”, a reality.
Spintronics—a portmanteau that means spin transport electronics—is the study of the intrinsic spin of electrons and its magnetic movement, in addition to its electronic charge, in solid-state devices.
Classical computers rely on massive amounts of electricity for computing and data storage, and they generate lots of wasted heat as a by-product.
In search of a more efficient alternative, researchers and engineers have turned to spintronics. In fact, it is widely considered to be one of today’s most important emerging research areas with an immense potential to provide high-speed, low-power logic and memory electronic devices.
Rather than using electricity, spintronic devices use the spin-wave, a property of electrons, in magnetic materials that have a lattice arrangement. This involves the modulation of spin-wave properties for measurable output that can be correlated to computation.
MIT’s circuit design enables precise control of computing with magnetic waves. This circuit architecture uses only a nanometer-wide domain wall in layered nanofilms of magnetic material to modulate a passing spin-wave. This is achieved without any extra components or electrical current.
The spin-wave can be turned to control the location of the wall as and when it is needed. This enables control of two changing spin-wave states which correspond to binary zeroes and ones.
In the future, it is thought that pairs of spin waves can be fed into the circuit through dual channels and combined to generate measurable quantum interference. Researchers hypothesize that these could execute complex tasks that today’s computers struggle with.
The nanometer-sized barrier illustrating different spin directions. Image courtesy of MIT News.
Researchers used a customized “magnetic domain wall”, a nanometer-sized barrier separating two neighboring magnetic structures, and layered a pattern of cobalt/nickel nanofilms with magnetic properties that can handle a high volume of spin waves. This wall was then placed in the middle of the magnetic material with a special lattice structure. This was then incorporated into a circuit.
On one half of the circuit, researchers excited constant spin waves. As the wave passes through the wall, its magnons begin to spin in the opposite direction. Magnons in the first region spin north while those past the wall in the second region spin south.
This causes a shift in the wave’s phase and a slight decrease in magnitude.
In their experiment, the researchers placed an antenna on the opposite side of the circuit to detect an output signal. Results indicated that, at its output state, the input wave flipped 180 degrees and that the wave’s magnitude had decreased.
The researchers then discovered a mutual interaction between the spin-wave and domain wall. This enabled them to toggle between two states. With the domain wall that can have its position changed by controlling the spin-wave, the circuit has a split, modulated wave. This wall can be positioned anywhere along the material block, and it is these which researchers believe will enable practical wave-based computing.
Luqiao Lin, the principal investigator of the Spintronic Material and Device Group and professor in the Department of Electrical Engineering and Computer Science at MIT, stated, “People are beginning to look for computing beyond silicon. Wave computing is a promising alternative. By using this narrow domain wall, we can modulate the spin-wave and create these two separate states, without any real energy costs. We just rely on spin waves and intrinsic magnetic material.”
