High-throughput electronic structure analysis using composition-spread films
A one-day experiment at NanoTerasu identifying the optimal half-metal composition accelerates the development of spintronic materials
image: 3 GeV High-Brilliance Synchrotron Radiation Facility: NanoTerasu
Credit: Yuya Sakuraba, National Institute for Materials Science; Susumu Yamamoto, Tohoku University; Hiroyuki Yamane, Photon Science Innovation Center
A research team comprising members from the National Institute for Materials Science (NIMS), Tohoku University, and the Photon Science Innovation Center (PhoSIC) has successfully identified the optimal composition of a Co-Mn-Si Heusler alloy exhibiting the highest spin polarization—a key property of half-metallic materials—in just one day of experiments. This achievement was made possible by fabricating a composition-spread thin film on a single substrate and conducting photoelectron measurements at a 3 GeV high-brilliance synchrotron radiation facility, NanoTerasu. This highly efficient optimization approach is expected to accelerate the development of high-performance spintronic materials.
Half-metallic materials are magnetic materials characterized by a high spin polarization, in which the spins of conduction electrons are aligned in a single direction. These materials are attracting attention as promising electrode candidates for next-generation hard disk drive read heads and other spintronic devices. However, direct measurement of spin polarization typically requires spin-resolved photoemission spectroscopy using low-energy photons in the VUV and soft X-ray regions, which is time-consuming. Therefore, faster methods for evaluating spin polarization are in increasing demand to enable more efficient materials development.
To address this challenge, the research team set out to develop a new and efficient method for optimizing the composition of half-metallic materials. They focused on Co₂MnSi, a well-known representative half-metal, and fabricated a thin film on a single substrate with a gradient in the atomic composition ratio of cobalt (Co) and manganese (Mn), ranging from 10 to 40 at.%. Hard X-ray photoelectron spectroscopy (HAXPES) measurements using synchrotron radiation were carried out at a hard X-ray beamline BL09U of NanoTerasu. As a result, a large dataset on the composition-dependent electronic structure was obtained in just one day, and detailed analysis identified that the highest spin polarization is achieved around the composition with 27 at.% Mn.
Looking ahead, this method is expected to accelerate the discovery and development of novel half-metallic materials, thereby contributing to the realization of high-performance spintronic devices.
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This research was conducted by a team comprising Dr. Ryo Toyama (NIMS Postdoctoral Researcher) and Dr. Yuya Sakuraba (Group Leader) from the Magnetic Functional Device Group, NIMS; Dr. Koichiro Yaji (Group Leader) and Dr. Shunsuke Tsuda (Senior Researcher) from the Photoemission Spectroscopy Group, NIMS; and Dr. Yuma Iwasaki (Senior Researcher) from the Data-Driven Materials Design Group, NIMS. The team also included Associate Professor Susumu Yamamoto from the International Center for Synchrotron Radiation Innovation Smart (SRIS), Tohoku University, and Dr. Hiroyuki Yamane (Chief Scientist) from the Photon Science Innovation Center (PhoSIC). The study was carried out as part of the JST CREST program “Exploring Innovative Materials in Unknown Search Space” (Grant Number: JPMJCR21O1).
The results of this research were selected as an Editor’s Choice in Science and Technology of Advanced Materials and published online on January 7, 2025.