Quantum Materials Synthesis | Advanced Characterization

Oxide interfaces control magnetic twists

Illustration of a magnetic skyrmion that induces an emergent electromagnetic field, yielding the topological Hall effect by deflecting electrons. Nanometer-scale magnetic skyrmions as small as 10 nm were created in LaMnO3/SrIrO3 superlattices where interface symmetry is tailored to increase magnetic exchange interactions.

Reearchers discovered a chiral spin texture in 3d-5d transition-metal oxide heterostructures that is highly tunable by controlling interface symmetry, yielding topological Hall effects.1 The ability to manipulate orbital-driven interactions that direct handed spin textures like nanometer-scale magnetic skyrmions opens a pathway to discover novel quantum materials that may be critical for the development of ultra-high-density information storage. 

Stacking LaMnO3 (3d) and SrIrO3 (5d) layers in a manner that aligns atoms and their spin orbitals allows immense control over magnetic exchange interactions resulting from the complex interplay between local magnetism, spin-orbit coupling, and charge that is unique to correlated oxide systems. LaMnO3/SrIrO3 superlattices were grown by pulsed laser deposition, and magnetic exchange, or Dzyaloshinskii-Moriya interactions (DMIs) were tuned. Measurements of correlated behavior demonstrated that interfacial symmetry can tunably transform the 3d-5d system from a ferromagnet to a chiral magnet. The skyrmions exhibit an enhanced electrical response known as the topological Hall effect. The extreme tunability of their magnetic ground state and associated electrical response arising from the spin topology have been previously unknown. These findings provide insights into the nature of DMIs creating chiral spin textures and point to potential quantum material systems to advance interface-driven topological phenomena.

E. Skoropata, J. Nichols, J. M. Ok, R. V. Chopdekar, E. S. Choi, A. Rastogi, C. Sohn, X. Gao, S. Yoon, T. Farmer, R. D. Desautels, Y. Choi, D. Haskel, J. W. Freeland, S. Okamoto, M. Brahlek, and H. N. Lee, Interfacial tuning of chiral magnetic interactions for large topological Hall effects in LaMnO3/SrIrO3 heterostructures, Sci. Adv. 6, eaaz3902 (2020); DOI: 10.1126/sciadv.aaz3902.

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