[Image Credits: Alexandre Debiève via Unsplash]
Electronic devices function on transferring signals via the charge of electrons. Most of our communication systems today consist of many small silicon-based devices that are fabricated on thin layers of semiconductors, interconnected by metals. But there is one problem — when electrons propagate in these metallic channels, heat is generated and the energy powering the devices is partially lost. The energy loss also limits the number of transistors packed into electronic devices.
In recent years, scientists have increasingly focussed on using an alternative method to transfer signals. This method utilises a fundamental property of matter, called ‘spin’, which creates magnetism. In magnetic materials, like iron, the electrons’ spins vary with time, and the collective precession gives rise to what physicists call ‘spin waves’. Electronic signals can propagate via these waves without generating heat, thus saving power and making the circuits cost-effective. More transistors can now be packed into electronic devices, reducing their size to few nanometres. Scientists call this new channel of signal propagation, ‘magnonic nanochannels’.
In a new study, an international group of scientists at the Satyendra Nath Bose National Centre for Basic Sciences (SNBNCBS), Kolkata, India, and the Center for Emergent Matter Science and Hitachi Ltd., Japan, have demonstrated a novel design of magnonic nanochannels. Funded by the Department of Science and Technology, Government of India, the Nano Spin Conversion Science and the RIKEN Incentive Research Project, Japan, the study was published in the journal Science Advances.
“We want to replace costly silicon-based materials with cheaper magnetic materials on the computers’ processing units,” says Anjan Barman, a senior professor at SNBNCBS and the corresponding author of the study. The researchers created multiple nanochannels parallel to each other, via which spin waves can propagate simultaneously. As a result, the signal processing speeds will significantly increase. “Previous studies have focused primarily on single nanochannels, but we have parallelised them,” he says.
The researchers used thin layers of magnetic materials and insulators superimposed on each other. Then, they set up alternate layers of electrodes across these layers and turned on the voltage. This electric field affects the magnetic layers to give rise to nanochannels. Moreover, the novel setup of equally spaced electric fields gives rise to parallel bands of nanochannels. “The fabrication of this device is completely new,” shares Anjan.
Then, the researchers carried out extensive calculations on a computer to show that the laws of physics, along with the known properties of the magnetic materials, independently predicted the parallel bands of nanochannels that they saw in their experiment. They also showed that when they turned off the voltage across the electrodes, the nanochannels would disappear. Thus, they could use the electric field to switch the system between ‘on’ and ‘off’ states.
The researchers shone light on the setup and observed its scattering by spin waves to record how quickly their setup processes the signal. They demonstrated that the frequency of the signal processing can be about tens to hundreds of gigahertz –– that’s one followed by eleven zeroes signals processed per second. In contrast, today’s electronic devices operate at only a few gigahertz. This is made possible by the property of spin waves and small size of the device, as the frequency of processing the signal increases if the size of the device is reduced.
The device is now ready for use in SNBNCBS, and similar such devices can be fabricated, say the researchers. “This technology can be immediately picked up by the industry, first via small startups and then later scaling up the production,” says Anjan. However, manufacturing such nanochannels at industrial scales and entirely replacing current electronic devices pose significant challenges. “Ensuring repeatability and reliability across a new device built of these nanochannels, with each unit below 50 nanometres in width, will be a technical challenge,” says Anjan. The researchers are in pursuit of beating them to design faster and better electronics.
This article has been run past the researchers, whose work is covered, to ensure accuracy.