Brand new physics advances next generation spintronics

Los Angeles CA (SPX) Jan 17, 2025
As global data demands surge, researchers are revolutionizing electronics with spintronics, a field that harnesses both the charge and spin of electrons to improve computing power and efficiency. Unlike traditional electronics, spintronics assigns binary values to electron spins (up = 0, down = 1), enabling faster and more energy-efficient data processing.

A recent study from the University of Utah and the University of California, Irvine (UCI), published in *Nature Nanotechnology* on January 15, 2025, reveals a novel phenomenon called anomalous Hall torque. This self-generated spin-orbit torque offers a new method for manipulating spin and magnetization via electrical currents, potentially advancing future technologies like neuromorphic computing, which mimics brain networks.

"This is brand new physics, which on its own is interesting, but there's also a lot of potential new applications that go along with it," said Eric Montoya, assistant professor of physics and astronomy at the University of Utah and lead author of the study. "These self-generated spin-torques are uniquely qualified for new types of computing like neuromorphic computing."

Understanding Hall torque

Electrons possess tiny magnetic fields that orient north ("up") or south ("down"), affecting their spin-orientation torque - the speed at which electrons spin around a fixed point. When electricity flows through certain materials, it organizes electrons based on spin, altering the material's magnetic and electronic properties.

Anomalous Hall torque derives from the anomalous Hall effect, first identified in 1881, which describes how electrons scatter asymmetrically in a magnetic material. This scattering creates a charge current perpendicular to the electric current. Similarly, anomalous Hall torque generates a spin current perpendicular to the electrical current, aligning the spin-orientation with the material's magnetization.

"It really comes down to the symmetry," Montoya explained. "The different Hall effects describe the symmetry of how efficiently we can control the spin-orientation in a material. As material scientists, we can really tune these properties to get devices to do different things."

A complete torque triad for spintronics

The discovery of anomalous Hall torque adds to the family of self-generated spin-orbit torques, including spin Hall torque and planar Hall torque. Together, these effects form a "Universal Hall torques" triad, providing a versatile framework for advancing spintronic devices. The study demonstrates that these torques should exist universally in conductive spintronic materials, offering researchers powerful tools to design next-generation technologies.

Traditional spintronic devices like Magnetoresistive Random Access Memory (MRAM) rely on layered ferromagnetic materials. Spin-torque MRAMs inject spin-polarized currents to flip the magnetic orientation between layers, encoding binary data more efficiently than conventional methods. The researchers' prototype simplifies this structure by transferring spin-orientation from a ferromagnetic conductor to an adjacent non-magnetic material, eliminating the need for multiple magnetic layers.

"We utilized anomalous Hall torque to create a nanoscale device known as a spin-torque oscillator. This device can mimic the functionality of a neuron, but is significantly smaller and operates at higher speeds," said Ilya Krivorotov, physicist at UCI and co-author of the study. "Our next step is to interconnect these devices into a larger network, enabling us to explore their potential for performing neuromorphic tasks, such as image recognition."

Research Report:Anomalous Hall spin current drives self-generated spin-orbit torque in a ferromagnet