Chirally coupled nanomagnets

Magnetically coupled nanomagnets have many potential applications including non-volatile memories, logic gates and sensors. In order to realize functional 2-D networks of coupled nanoscale magnetic elements such as those used for nanomagnet logic [1] and artificial spin ice [2], it is desirable to engineer effective lateral magnetic couplings in a controllable way. Up to now, this has been achieved by exploiting the long-range dipolar interaction. However, the dipolar interaction is non-local and scales inversely with the magnet volume, so limiting its use in applications involving nanometer sized structures and thin films.
In this work, we demonstrate an alternative method to control the lateral coupling between adjacent magnetic nanostructures [3] based on the interfacial Dzyaloshinskii-Moriya interaction (DMI). In particular, we have patterned regions with in-plane (IP) and out-of-plane (OOP) magnetic anisotropy in a magnetic element using selective oxidation of Pt/Co/Al films, and the magnetization in the OOP and IP parts of the islands are chirally coupled via DMI arising from the Pt underlayer, giving either ↓→ or ↑← configurations.
We have exploited this concept for various applications. For example, we have created stable synthetic lateral antiferromagnets, skyrmions with different numbers of IP rings and artificial spin ices based on a square lattice and kagome lattice. In addition, we have demonstrated field-free current-induced switching between multistate magnetic configurations in the chirally coupled thin-film nanomagnets via spin-orbit torques. Our work therefore provides a platform to design tailor-made arrays of correlated nanomagnets with a future perspective to achieve all-electric control of planar logic gates and memory devices.

[1] H. Arava, et al. Nanotechnology 29, 265205 (2018).
[2] L. Heyderman and R. Stamps, J. Phys.: Condens. Matter 25, 363201 (2013).
[3] Z. Luo, et al. Science 363, 1435 (2019).