‘Brand new physics’ for next generation spintronics

January 15, 2025

Our data-driven world demands more — more capacity, more efficiency, more computing power. To meet society’s insatiable need for electronic speed, physicists have been pushing the burgeoning field of spintronics.

 

Eric Montoya

Traditional electronics use the charge of electrons to encode, store and transmit information. Spintronic devices utilize both the charge and spin-orientation of electrons. By assigning a value to electron spin (up=0 and down=1), spintronic devices offer ultra-fast, energy-efficient platforms.

To develop viable spintronics, physicists must understand the quantum properties within materials. One property, known as spin-torque, is crucial for the electrical manipulation of magnetization that’s required for the next generations of storage and processing technologies.

Researchers at the University of Utah and the University of California, Irvine (UCI), have discovered a newtype of spin–orbit torque. The study that published in Nature Nanotechnology on Jan. 15, 2025, demonstrates a new way to manipulate spin and magnetization through electrical currents, a phenomenon that they’ve dubbed the anomalous Hall torque.

“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, an emerging system that mimics human brain networks.”

Hall of torques

Electrons have miniscule magnetic fields that, like planet Earth, are dipolar—some spins are oriented north (“up”) or south (“down”) or somewhere in between. Like magnets, opposite poles attract while like poles repel. Spin-orientation torque refers to the speed at which the electron spins around a fixed point.

In some materials, electricity will sort electrons based on their spin orientation. The distribution of spin-orientation, known as symmetry, will influence the material’s properties, such as the directional flow of a ferromagnet’s magnetic field.

Anomalous Hall torque is related to the well-known anomalous Hall effect, discovered by Edwin Hall in 1881. The anomalous Hall effect describes how electrons are scattered asymmetrically when they pass through a magnetic material, leading to a charge current that flows 90 degrees to the flow of an external electric current. It turns out, an analogous process occurs for spin—when an external electrical current is applied to a material, a spin current flows 90 degrees to the flow of electrical current with the spin-orientation along the direction of the magnetization.

“It really comes down to the symmetry. The different Hall effects describe the symmetry of how efficiently we can control the spin-orientation in a material,” Montoya said. “You can have one effect, or all effects in the same material. As material scientists, we can really tune these properties to get devices to do different things.”

Read the full story by Lisa Potter in @ The U.