Researchers from The Grainger College of Engineering at the University of Illinois Urbana-Champaign have developed the first magnetic multipole-based micromagnetic model for antiferromagnets. Published in Applied Physics Reviews , their generalized framework provides a theoretical and computational foundation for designing future spintronic devices made with antiferromagnetic materials.
Unlike traditional electronics, which rely on an electron's charge, spin electronics harnesses an electron's magnetic orientation, or spin. In recent years, materials science researchers have identified antiferromagnets as a promising material for future spintronic devices, thanks to their ultrafast spin dynamics and stability under external magnetic fields.
But before these materials can be implemented in practical devices, researchers need robust models that decipher their complex, non-uniform movements. Although micromagnetic simulations have been widely used to study spin dynamics in ferromagnets, a comparable framework had yet to be fully established for antiferromagnets, whose spin structure is more difficult to control. However, some types of antiferromagnets — such as noncollinear antiferromagnets — have a unique rotating structure that is more easily manipulated.
"We wanted to create a good numerical tool to study these more macroscopic domain functions, which are difficult to access with atomistic simulations alone," said Axel Hoffmann, a professor of materials science and engineering and the paper's senior author.
Using Mn₃Sn as a representative noncollinear antiferromagnetic material, Hoffmann worked with postdoctoral researcher Myoung-Woo Yoo to develop a micromagnetic model based on a magnetic octupole moment. Operating at the micrometer scale, the model captured important phenomena — like domain-wall dynamics and other spatially non-uniform magnetic textures — that could not be described by existing analytic models. Their findings also revealed domain-wall deformation and an effective inertial mass, providing new insight into mesoscopic magnetic-multipole dynamics in antiferromagnets.
"Our work demonstrates that magnetic multipoles can serve as effective order parameters for micromagnetic simulations of these systems," Hoffmann said.
The Illinois researchers' model may support the future development of enhanced spintronic technologies for information processing, signal generation and data storage. In the meantime, they aim to improve the current iteration, accounting for dynamic spin textures and comparing their results to those derived experimentally.
"Here we assume a magnetic fixed spin texture, but we know that the spins can be slightly deviated from the perfect triangular shape," Yoo said. "This can provide additional angular momentum, generating interesting high-frequency spin dynamics. In the future, we would like to incorporate this effect into the model and validate it through experiments."
Illinois Grainger Engineering Affiliations
Axel Hoffmann is an Illinois Grainger Engineering professor in the Department of Materials Science and Engineering . He holds the founder professor appointment.
