The exchange coupling underlies ferroic magnetic coupling and is thus the key element that governs statics and dynamics of magnetic systems. This fundamental interaction comes in two flavors - symmetric and antisymmetric coupling. While symmetric coupling leads to ferro- and antiferromagnetism, antisymmetric coupling has attracted significant interest owing to its major role in promoting topologically non-trivial spin textures that promise high-speed and energy-efficient devices. So far, the antisymmetric exchange coupling rather short-ranged and limited to a single magnetic layer has been demonstrated, while the symmetric coupling also leads to long-range interlayer exchange coupling. Here, we report the missing component of the long-range antisymmetric interlayer exchange coupling in perpendicularly magnetized synthetic antiferromagnets with parallel and antiparallel magnetization alignments. Asymmetric hysteresis loops under an in-plane field unambiguously reveal a unidirectional and chiral nature of this novel interaction, which cannot be accounted for by existing coupling mechanisms, resulting in canted magnetization alignments. This can be explained by spin-orbit coupling combined with reduced symmetry in multilayers. This new class of chiral interaction provides an additional degree of freedom for engineering magnetic structures and promises to enable a new class of three-dimensional topological structures.
@article{arxiv.1809.01080,
title = {Chiral magnetic interlayer coupling in synthetic antiferromagnets},
author = {Dong-Soo Han and Kyujoon Lee and Jan-Philipp Hanke and Yuriy Mokrousov and Kyoung-Whan Kim and Woosuk Yoo and Tae-Wan Kim and Reinoud Lavijsen and Chun-Yeol You and Henk J. M. Swagten and Myung-Hwa Jung and Mathias Klaeui},
journal= {arXiv preprint arXiv:1809.01080},
year = {2019}
}