Researchers from Martin Luther University Halle-Wittenberg (MLU) and the Max Planck Institute of Microstructure Physics in Halle have developed a groundbreaking method to analyze magnetic nanostructures with exceptional precision.
This technique achieves a resolution of approximately 70 nanometers, far surpassing the 500-nanometer limit of conventional light microscopes. The advancement holds significant potential for developing new energy-efficient storage technologies based on spin electronics. The team’s findings are detailed in the latest issue of ACS Nano.
Breakthrough in Nanoscale Imaging
Conventional optical microscopes are limited by the wavelength of light, making it impossible to resolve details smaller than approximately 500 nanometers. A new method has overcome this barrier by harnessing the anomalous Nernst effect (ANE) and a metallic nanoscale tip. ANE generates an electrical voltage in a magnetic metal that is perpendicular to both its magnetization and a temperature gradient.
“A laser beam focuses on the tip of a force microscope and thus causes a temperature gradient on the surface of the sample that is spatially limited to the nanoscale,” explains Professor Georg Woltersdorf from the Institute of Physics at MLU. “The metallic tip acts like an antenna and focuses the electromagnetic field in a tiny area below its apex.”
This innovative approach allows ANE-based imaging with far higher resolution than conventional light microscopy. The team’s published images achieve an impressive resolution of around 70 nanometers.
Advancing Magnetic Structure Analysis
Earlier studies primarily focused on magnetic polarization within the sample plane. However, the research team demonstrated that the in-plane temperature gradient is also critical, enabling the investigation of out-of-plane polarization through ANE measurements. To validate the reliability of this method for visualizing magnetic structures at the nanometer scale, the researchers applied it to a magnetic vortex structure.
Enhancing Spintronic Imaging and Applications
A particular advantage of the new technique is that it also works with chiral antiferromagnetic materials.
“Our findings are significant for the thermoelectric imaging of spintronic components. We have already demonstrated this with chiral antiferromagnets,” says Woltersdorf.
“With our method has two advantages: on the one hand, we have greatly improved the spatial resolution of magnetic structures, far beyond the possibilities of optical methods. Secondly, it can also be applied to chiral antiferromagnetic systems, which will directly benefit our planned Cluster of Excellence ‘Centre for Chiral Electronics’,” says Woltersdorf.
Together with Freie Universität Berlin, the University of Regensburg, and the Max Planck Institute of Microstructure Physics in Halle, MLU is applying for funding as part of the Excellence Strategy. The aim of the research is to lay the foundations for new concepts for the electronics of the future.
Reference: “Anomalous Nernst Effect-Based Near-Field Imaging of Magnetic Nanostructures” by Atul Pandey, Jitul Deka, Jiho Yoon, Anagha Mathew, Chris Koerner, Rouven Dreyer, James M. Taylor, Stuart S. P. Parkin and Georg Woltersdorf, 5 November 2024, ACS Nano.
DOI: 10.1021/acsnano.4c09749
The work was funded by the German Research Foundation (DFG) as part of the Collaborative Research Centre / Transregio (CRC TRR) 227, Project-1D 328545488.
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