Researchers use unique material to control spin polarization

Researchers used the Advanced Photon Source (APS), a U.S. Department of Energy Office of Science User Facility at DOE’s Argonne National Laboratory, to study ways to manipulate electron spins and develop new materials for spintronics. The research team, led by Chang-Beom Eom at the University of Wisconsin-Madison, designed a new material that has three times the storage density and uses much less power than other spintronics devices.

Not many of these types of materials exist, especially ones that work at room temperature like this one. If the new material can be perfected, it could aid in the creation of more efficient electronic devices with less tendency to overheat. This is particularly important for advancing the development of low-power computing and fast magnetic memory.

The new structure is based on an unusual class of materials called antiperovskites that the team used in order to manipulate the flow of spin information without moving the electrons’ charges through the material. To figure out if it worked, and to better understand the structure of the material, Eom’s team used X-ray diffraction at the APS to see at what point the structure of the material changed, indicating the emergence of the necessary arrangement of electronic spins.

“In one week of time at the APS we can do a month’s worth of work,” Eom said.

Before the study, APS beamline scientists Phil Ryan and Jong-Woo Kim spent time with Eom, helping him determine when he had the right structure as he grew these new materials in his lab.

“If they have a scientific question, we discuss it and together design an experiment at APS to answer the question,” said Kim, a physicist at APS collaborating with Eom’s research team. ​“We understand our techniques and capabilities very well, so we can contribute to the design of the experiment, or even shape the conversation.”

For this study, Eom used the APS to look at the lattice structure of the material at the atomic level as it cooled toward room temperature. Using X-ray diffraction, they measured the lattice parameter — basically the distance between atoms — and extracted the separation of the atoms as the temperature of the material changed.

“This material develops a magnetic order a little above room temperature,” said Ryan, another physicist at APS who worked with Eom on this project as well as many others over the years. ​“Once the electron spins order themselves, the atoms are pushed slightly away from each other. So even though we couldn’t directly detect the structure with X-rays, we monitored and measured this structural change with temperature at the APS to confirm the emergence of this magnetic order.”

This was one of the three techniques used in the study to measure the arrangement of electronic spins, and this data, in conjunction with other measurements, helped solidify and cement the validity of the findings.

“The ability to manipulate the arrangement of electronic spins, as well as their movement through material, has tremendous possibilities for more energy-efficient devices,” Eom said. ​“This is the first step in demonstrating how to do it.”