物理講壇2020年第36講：Recent Advances on Theoretical Study of Dzyaloshinskii-Moriya interaction at Interface
The interfacial Dzyaloshinskii-Moriya interaction (DMI) has attracted significant interest because it plays a tremendous role for fast domain wall motion and allows creation of topological textures, magnetic skyrmions, which are very promising for ultra-dense/ultra low-energy consumption information storage and spintronic devices.
A standard ingredient in such devices is an interface between a ferromagnetic metal and a heavy nonmagnetic metal; this interface governs a mechanism proposed by A. Fert and P. Levy in the 80’s, where the heavy metal provides large spin orbit coupling as the energy source to obtain a strong DMI. However, in case of this so-called Fert-Levy type interaction the large spin orbit coupling of the heavy metal is detrimental to performance in device applications. Therefore, looking for materials that are free of heavy metals and yet provide large DMI is critical for their applications in spintronic devices.
I will report the discovery that graphene offers a solution in the long quest to replace heavy metals. The concept was demonstrated by first principles calculations and real-space observations, finding that significant DMI can be realized at graphene/ferromagnet interfaces, in absence of heavy metals.[1,2]
This DMI is predominantly located at the atomic Co layer directly adjacent to the graphene, and it originates from a Rashba effect. Beyond materials based on the Fert-Levy mechanism, the findings described in this work thus provide a new path for the discovery of a range of topological magnetic materials based on the Rashba effect. These new materials may well prove to be of enormous value in the development of skyrmion- and domain wall-based logic and memory devices.
Given the hot current interest in this topic, this work concisely uncovers the microscopic details of the DMI from first principles and experiments, demonstrating an unexpected new property of graphene/ferromagnet interfaces for the first time. This work is therefore one of the first towards a novel field of research called graphene spin-orbitronics, a next generation of graphene spintronics, i.e. they are proposing progress beyond state-of-the-art in these fields of science.
Nest, I will report the DMI beyond heterostructures, i.e. using Janus 2D magnets to obtain large DMI and create topological magnetic structures. [3,4]
 “Anatomy of Dzyaloshinskii-Moriya Interaction at Co/Pt Interfaces” H Yang, A Thiaville, S Rohart, A Fert, M Chshiev, Physical Review Letters 115, 267210 (2015)
 “Significant Dzyaloshinskii–Moriya interaction at graphene–ferromagnet interfaces due to the Rashba effect” Hongxin Yang, Gong Chen, Alexandre A.C. Cotta, Alpha T. N'Diaye, Sergey A. Nikolaev, Edmar A. Soares, Waldemar A. A. Macedo, Andreas K. Schmid, Albert Fert, and Mairbek Chshiev, Nature Materials 17, 605–609 (2018)
 “Very large Dzyaloshinskii-Moriya interaction in two-dimensional Janus manganese dichalcogenides and its application to realize skyrmion states”J Liang, W Wang, H Du, A Hallal, K Garcia, M Chshiev, A Fert, H Yang
Physical Review B 101, 184401 (2020) (Editors’ suggestion)
 “Strain-tunable ferromagnetism and chiral spin textures in two-dimensional Janus chromium dichalcogenides”Q Cui, J Liang, Z Shao, P Cui, H YangPhysical Review B 102, 094425 (2020)