Effects of the interfacial Dzyaloshinskii–Moriya interaction on magnetic dynamics

Abstract

In the ‘Beyond Moore’s Law’ era, information devices are expected to exhibit advantages, including small sizes, high processing speeds, and low power and dissipation. Novel magnetic information devices with these advantages are made of heavy metal (HM)/ferromagnet (FM) composites. Owing to an asymmetric structure, the anisotropic exchange coupling, named the interfacial Dzyaloshinskii–Moriya interaction (iDMI), is generated at the HM/FM interface. This iDMI plays a fundamental role in stabilizing non-trivial topological magnetic solitons, such as magnetic skyrmions and chiral domain walls (DWs). On the other hand, the iDMI also influences the magnetic dynamics, including ferromagnetic resonance (FMR), spin wave, and the motion of the chiral DWs and skyrmions. These magnetic dynamic behaviors are the base of the functions of novel magnetic information devices. Therefore, the influence of the iDMI on magnetic dynamics has attracted wide attention in recent years. In this topical review, we give a detailed introduction to and discussion about recent investigations of the iDMI-relevant magnetic dynamics of HM/FM bilayer systems. Especially, this review concentrates on the individual contributions of the inner iDMI and the boundary iDMI to magnetic dynamics. This review consists of the following sections: (a) an introduction about the background, the basic theory of magnetic dynamics, and the iDMI; (b) a review of the effects of the iDMI on the propagation of spin wave. Owing to the iDMI, the dispersion relationship of the spin wave is asymmetric, which results in various interesting phenomena. This not only offers a precise method for measuring the iDMI constant, but also gives rise to potential applications for novel magnonic devices. (c) A review of the effects of the iDMI on FMR. In general, the iDMI is thought to have little impact on the FMR for uniform precession. However, a unique iDMI-relevant mode was still observed in the FMR spectra owing to the non-parallel alignment of magnetic moments as a result of the boundary iDMI. (d) A review about the motion of DWs with a chiral structure due to the iDMI. The iDMI plays a fundamental role in the high velocity of the chiral DWs. Meanwhile, the iDMI also results in the tilting of the DW plane, and the mechanism for this tilting has been widely investigated. The tilting of the DW plane may be depressed by the interlayer exchange coupling. (e) Finally, we summarize the review and give an outlook.