Physicists switch magnetic state using spin current
An illustration shows the unconventional charge to spin transduction in a quantum material with low-symmetry crystal structure. (Left) A model showing the crystal structure of WTe2, where a-axis and b-axis are labeled. The crystal is invariant (noninvariant) upon a bc (ac) mirror operation. (Top right) When a charge current (shown by yellow arrow) is applied along the b-axis, there is only in-plane component of spin polarization as shown by green arrows. (Bottom right) One the other hand, when a charge current is applied along the a-axis, there is an out-of-plane component of the spin polarization as shown by green arrows. This out-of-plane oriented spin current is used to switch the magnetization in this work. Credit: Carnegie Mellon University

I-Hsuan Kao and Ryan Muzzio were working on a switch. After that, it's off.

Working in the Department of Physics' Lab for Investigating Quantum Materials, Interfaces and Devices, Kao, Muzzio and other research partners were able to show proof of concept that running an electrical current through a novel two-dimensional material could control the magnetic state.

The work, which was published in Nature Materials in June and has a patent pending, has the potential to be used for data storage in consumer products.

Kao, who was the first author on the paper, said that they were using ultrathin materials and stacking them on top of each other to create high quality devices.

The LIQUID Group is headed by an assistant professor of physics and an assistant professor of physics.

Singh saidSpins and magnetism are everywhere. Material properties are dictated by atoms configuration on an atomic lattice. It has a low-symmetry crystal structure that allows us to generate a special kind of spin current.

The way atoms are configured in WTe 2 allows for an out-of-plane spin current that can be used to control a magnet. In order to switch the magnetic state of most magnetic materials using spin current, a magnetic field is applied horizontally or in the plane. Energy efficient data storage and logic devices can be made with a material that can switch magnetism without a magnetic field.

The potential of realizing high-speed and densely packed data storage bits while using less power is what the work could be applied to.

Muzzio said that people can use an electric field to generate in-plane oriented spin current and use it to switch the magnetization from an up state to a down state or vice-versa. The property of breaking symmetry is what this is all about.

Kao and Muzzio were both experts on magnetism and studies of electrons in material systems. Over the course of two years, Kao and Muzzio created more than twenty devices.

Kao said that the simple devices allow a switch to be turned in either an up position or a down position, which is similar to a zero and a one in a single letter. The thickness of the device is less than 1/200th of a human hair.

Muzzio said that they had just scratched the surface of what the material could do. There is so much more we can do with this material. There is more to come.

More information: I-Hsuan Kao et al, Deterministic switching of a perpendicularly polarized magnet using unconventional spin–orbit torques in WTe2, Nature Materials (2022). DOI: 10.1038/s41563-022-01275-5 Journal information: Nature Materials