GMW Best Poster Award 1 - Experimental correlation of Interfacial Dzyaloshinskii-Moriya interaction amplitude and Work Function in magnetic multilayers

Abstract

Authors: F. Ajejas, W. Legrand, Y. Sassi, S. Collin, A. Vecchiola, K. Bouzehouane, N. Reyren, V. Cros, A. Fert, Unite Mixte de Physique CNRS/Thales, Palaiseau, Île-de-France, FRANCE|S. Pizzini, Institut NEEL, Grenoble, Auvergne-Rhône-Alpes , FRANCE| Abstract Body: Magnetic multilayers (MML) with large perpendicular magnetic anisotropy (PMA) and Dzyaloshinskii-Moriya interaction (DMI) have attracted great attention in recent years owing to the possibility of stabilizing non-collinear magnetic textures such as chiral domain walls (DW) [1], spin spirals [2] or skyrmions [3-4] with Neeel chiral spin rotation. The latter are promising candidates as carriers of information for next-generation race-track magnetic memories or logic devices. To this aim, the accurate experimental determination of DMI is an important challenge allowing the engineering of future devices with tailored properties. The determination of the effective DMI amplitude D in MML is still a current subject of research, in particular for metallic multilayers with a high number of repetitions. In this study, we have performed a series of measurements to determine DMI values by two different techniques: domain size periodicity (λ) [5] of aligned-stripe domains after in-plane (IP) demagnetization by magnetic force microscopy (MFM), and asymmetric expansion of domains in the presence of an in-plane magnetic field, by Kerr microscopy [6-7]. For this purpose, we selected different materials to build asymmetric trilayers, with the general structure is [Pt/Co/M]xN with M = Ru, Ni, Pd, Al, Al/Ta and N = 2, 3, 4, 5, 6 the number of repetitions. We observe a correlation between Ds = D/t (t is the Co thickness), the interfacial DMI obtained in the previous methods and intrinsic material parameters such as atomic number (Z), Pauling electronegativity (χ) [8] work function (Wf) [9] of Co/M interfaces. We find a clear linear behaviour between Ds and Wf. This correlation points to Rashba-like interfacial fields, leading to the modulation of the effective interfacial DMI. French ANR grant TOPSky TOPSKY (ANR-17-CE24-0025) and DARPA TEE program grant (MIPR#HR0011831554) and EU grant SKYTOP (H2020 FET Proactive 824123) are acknowledged for their financial support.