Researchers use heat to drive topological spin texture transformations

Researchers at Japan's RIKEN have conducted an experiment that could help the development of new energy-efficient spintronics devices. They used heat and magnetic fields to create transformations between spin textures—magnetic vortices and antivortices known as skyrmions and antiskyrmions—in a single crystal thin plate device. What's even more important is that they achieved this at room temperature.

Skyrmions and antiskyrmions, which are textures that exist within special magnetic materials involving the spin of the electrons in the material, are an active area of research, as they could be used for next-generation memory devices, for example, with skyrmions acting as a "1" bit and antiskyrmions a "0" bit. In the past, scientists have been able to move them in a variety of ways, and to create transformations between them using electric current. However, because current electronic devices consume electrical power and produce waste heat, the researchers in the group, led by Xiuzhen Yu at the RIKEN Center for Emergent Matter Science, decided to see if they could find a way to create the transformations using heat gradients.


To perform the research, the team used a focused-ion beam—an extremely precise fabrication system—to create a microdevice from the bulk single crystal magnet (Fe0.63Ni0.3Pd0.07)3P, composed of iron, nickel, palladium, and phosphorous atoms, and then used Lorentz scanning microscopy—an advanced method for examining the magnetic properties of materials at very small scales.

The scientists found that when a temperature gradient was applied to the crystal simultaneously with a magnetic field, at room temperature, the antiskyrmions within it transformed first into non-topological bubbles—a sort of transition state between skyrmions and antiskyrmions—and then to skyrmions, as the temperature gradient was raised. They then remained in stable configuration as skyrmions even when the thermal gradient was eliminated.

This finding was consistent with theoretical expectations, but a second finding surprised the group. They were surprised to find that when the magnetic field was not applied, the thermal gradient led to a transformation from skyrmions to antiskyrmions, which also remained stable within the material. This is exciting because it means that it's possible to use a thermal gradient—basically using waste heat—to drive a transformation between skyrmions and antiskyrmions, depending on whether a magnetic field is applied or not. Doing this at room temperature is a major point as well. This could open the way to a new type of information storage devices such as nonvolatile memory devices using waste heat.

The team plans to continue its work to manipulate skyrmions and antiskyrmions in new and more efficient ways, including the thermal control of antiskyrmion motion, with the goal to build actual thermospintronic and other spintronics devices that could be used in everyday lives. 

Posted: Jan 13,2024 by Roni Peleg