Spintronics Breakthrough – Scientists Confirm a Previously Undetected Physics Phenomenon

Research suggests a novel approach to enhance spintronics, paving the way for advancements in future technology.

In a new breakthrough, researchers have used a novel technique to confirm a previously undetected physics phenomenon that could be used to improve data storage in the next generation of computer devices. 

Spintronic memories, utilized in advanced computers and satellites, leverage the magnetic states produced by the intrinsic angular momentum of electrons for data storage and retrieval. Depending on its physical motion, an electron’s spin produces a magnetic current. Known as the “spin Hall effect,” this has key applications for magnetic materials across many different fields, ranging from low-power electronics to fundamental quantum mechanics. 

More recently, scientists have found that electrons are also capable of generating electricity through a second kind of movement: orbital angular momentum, similar to how Earth revolves around the sun. This is known as the “orbital Hall effect,” said Roland Kawakami, co-author of the study and a professor in physics at The Ohio State University. 

A Method to Observe the Orbital Hall Effect

Theorists predicted that by using light transition metals – materials that have weak spin Hall currents – magnetic currents generated by the orbital Hall effect would be easier to spot flowing alongside them. Until now, directly detecting such a thing has been a challenge, but the study, led by Igor Lyalin, a graduate student in physics, and published in the journal Physical Review LettersPhysical Review Letters (PRL) is a peer-reviewed scientific journal published by the American Physical Society. It is one of the most prestigious and influential journals in physics, with a high impact factor and a reputation for publishing groundbreaking research in all areas of physics, from particle physics to condensed matter physics and beyond. PRL is known for its rigorous standards and short article format, with a maximum length of four pages, making it an important venue for rapid communication of new findings and ideas in the physics community.” data-gt-translate-attributes=”[{“attribute”:”data-cmtooltip”, “format”:”html”}]” tabindex=”0″ role=”link”>Physical Review Letters, showed a method to observe the effect.

“Over the decades, there’s been a continuous discovery of various Hall effects,‘’ said Kawakami. “But the idea of these orbital currents is really a brand new one. The difficulty is that they are mixed with spin currents in typical heavy metals and it’s difficult to tell them apart.” 

Instead, Kawakami’s team demonstrated the orbital Hall effect by reflecting polarized light, in this case, a laser, onto various thin films of the light metal chromium to probe the metal’s atoms for a potential build-up of orbital angular momentum. After nearly a year of painstaking measurements, researchers were able to detect a clear magneto-optical signal which showed that electrons gathered at one end of the film exhibited strong orbital Hall effect characteristics. 

Implications for Future Spintronics Applications

This successful detection could have huge consequences for future spintronics applications, said Kawakami.

“The concept of spintronics has been around for about 25 years or so, and while it’s been really good for various memory applications, now people are trying to go further,” he said. “Now, one of the field’s biggest goals is to reduce the amount of energy consumed because that’s the limiting factor for jacking up performance.”

Lowering the total amount of energy needed for future magnetic materials to operate well could potentially enable lower power consumption, higher speeds, and higher reliability, as well as help to extend the technology’s lifespan. Utilizing orbital currents instead of spin currents could possibly save both time and money in the long term, said Kawakami. 

Noting that this research opens up a way to learn more about how these strange physics phenomena arise in other kinds of metals, the researchers say they want to continue delving into 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.
DOI: 10.1103/PhysRevLett.131.156702

Co-authors were Sanaz Alikhah and Peter M. Oppeneer of Uppsala University and Marco Berritta of both 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.