Breakthrough in Spintronics: Confirmation of a Previously Unidentified Physics Phenomenon

In a recent scientific study, researchers have substantiated the existence of the “orbital Hall effect,” an intriguing phenomenon with the potential to revolutionize data storage in forthcoming computer devices. This significant discovery, which entails the generation of electricity via the orbital movement of electrons, promises remarkable advancements in the realm of spintronics, ultimately leading to more efficient, faster, and more reliable magnetic materials. This breakthrough has the potential to reshape the landscape of technology in the near future.

Spintronics, a critical component of advanced computer systems and satellites, relies on the manipulation of magnetic states facilitated by the inherent angular momentum of electrons for data storage and retrieval. The spin of an electron generates a magnetic current contingent upon its physical motion, a phenomenon known as the “spin Hall effect.” This effect holds diverse applications across multiple fields, spanning from low-power electronics to fundamental quantum mechanics.

In recent developments, researchers have unveiled an additional capability of electrons, namely, the generation of electricity through a distinct type of motion referred to as orbital angular momentum. This motion resembles the Earth’s orbit around the sun and has been termed the “orbital Hall effect.” Roland Kawakami, co-author of the study and a physics professor at The Ohio State University, elucidated this phenomenon.

Theoretical predictions suggested that the detection of magnetic currents stemming from the orbital Hall effect could be facilitated by employing light transition metals, materials characterized by feeble spin Hall currents. Until now, directly observing such currents had posed a formidable challenge. However, the study, spearheaded by Igor Lyalin, a graduate student in physics, and published in the journal Physical Review Letters, unveiled a method to witness this elusive effect.

Kawakami pointed out that over the years, various Hall effects had been discovered, but the concept of orbital currents was a groundbreaking one. Distinguishing these currents from spin currents in conventional heavy metals had proven to be a daunting task. Kawakami’s team successfully demonstrated the orbital Hall effect by directing polarized light, specifically a laser, onto thin films of the light metal chromium. This illuminated the metal’s atoms and allowed researchers to detect a conspicuous magneto-optical signal, indicating the accumulation of electrons at one end of the film exhibiting robust orbital Hall effect characteristics.

The implications of this breakthrough for future spintronics applications are monumental. Kawakami emphasized that while spintronics has made significant strides in various memory applications over the past 25 years, the field’s current focus is on minimizing energy consumption, a key limitation to enhancing performance. Reducing the energy requirements of future magnetic materials could potentially lead to lower power consumption, increased speed, enhanced reliability, and prolonged technology lifespan. Shifting from spin currents to orbital currents could offer long-term benefits in terms of both time and cost savings.

The researchers, acknowledging that their findings shed light on the emergence of these intriguing physics phenomena in other metal types, expressed their commitment to further investigating the intricate relationship between spin Hall effects and orbital Hall effects.

This groundbreaking research was conducted in collaboration with co-authors Sanaz Alikhah and Peter M. Oppeneer from Uppsala University, along with Marco Berritta, affiliated with both Uppsala University and the University of Exeter. The study received support from the National Science Foundation, the Swedish Research Council, the Swedish National Infrastructure for Computing, and the K. and A. Wallenberg Foundation.

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.

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More about Spintronics Advancement

• Physical Review Letters – “Magneto-Optical Detection of the Orbital Hall Effect in Chromium”
• The Ohio State University – Department of Physics
• Uppsala University
• University of Exeter
• National Science Foundation
• Swedish Research Council
• Swedish National Infrastructure for Computing
• K. and A. Wallenberg Foundation