The research suggests a new method to improve spintronics, paving the way for future technological advances.
In a new breakthrough, researchers have used a novel technique to confirm an unprecedented physics phenomenon that can be used to improve data storage in the next generation of computing devices. .
Spintronic memories, used in advanced computers and satellites, take advantage of magnetic states created by the intrinsic angular momentum of electrons for data storage and retrieval. Depending on its physical motion, the spin of the electron produces a magnetic current. Known as the “spin Hall effect,” this has important applications for magnetic materials in many different fields, from low-power electronics to fundamental quantum mechanics.
Recently, scientists have found that electrons can also generate electricity through a second type of motion: orbital angular momentum, similar to how the Earth revolves around the sun. This is known as the “orbital Hall effect,” said Roland Kawakami, co-author of the study and a professor of physics at The Ohio State University.
A Method for Observing the Orbital Hall Effect
Theorists predict that by using light transition metals – materials with weak spin Hall currents – the magnetic currents generated by the orbital Hall effect will be easier to see flowing alongside this. Until now, direct detection of such an object has been a challenge, but the study, led by Igor Lyalin, a graduate student in physics, and published in the journal Physical Review Lettersshows a method to observe the effect.
“For decades, there has been continuous discovery of various Hall effects,” Kawakami said. “But the idea of these orbital currents is a new one. The difficulty is that they are mixed with the currents of rotation of common heavy metals and it is difficult to tell them apart. ”
Instead, Kawakami’s team demonstrated the orbital Hall effect by shining polarized light, in this case, a laser, onto various thin films of the light metal chromium to probe the metal atoms for of the potential build-up of orbital angular momentum. After nearly a year of painstaking measurements, the researchers were able to detect a clear magneto-optical signal indicating that the electrons gathered at one end of the film reflect the strong orbital Hall effect characteristics.
Implications for Future Applications of Spintronics
This successful detection could have far-reaching consequences for future spintronics applications, Kawakami said.
“The concept of spintronics has been around for about 25 years or so, and although it’s very good for various memory applications, now people are trying to go further,” he said. “Today, one of the biggest goals in the field is to reduce the amount of energy consumed because that is the limiting factor in increasing performance.”
Lowering the total amount of energy required for future magnetic materials to function effectively will enable lower power consumption, higher speed, and greater reliability, as well helps to extend the life of the technology. The use of orbital currents instead of spin currents may save time and money in the long term, said Kawakami.
Noting that this research opens up a way to learn more about how these strange physical phenomena arise in other types of metals, the researchers say they want to continue investigating the complex connection between spin Hall effects and orbital Hall effects.
Reference: “Magneto-Optical Detection of the Orbital Hall Effect in Chromium” by Igor Lyalin, Sanaz Alikhah, Marco Berritta, Peter M. Oppeneer and Roland K. Kawakami, 11 October 2023, Physical Review Letters.
Co-authors are Sanaz Alikhah and Peter M. Oppeneer of Uppsala University and Marco Berritta of Uppsala University and the University of Exeter. This work was supported by the National Science Foundation, the Swedish Research Council, the Swedish National Infrastructure for Computing, and the K. and A. Wallenberg Foundation.
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