Evidence of the interfacial Dzyaloshinskii-Moriya interaction in Ni80Fe20/graphene using Bragg-MOKE

Abstract

The Dzyaloshinskii-Moriya interaction (DMI) plays a crucial role in the stabilization of chiral spin textures [1]. Interfacial DMI (iDMI) induced by a lack of inversion symmetry and strong spin orbit coupling at the interface of Ferromagnet/Heavy Metal (FM/HM) heterostructures provides various opportunities for future spintronic devices. Recently, iDMI in a thin film of NiFe/Graphene (NiFe/Gr) heterostructures has been detected using Brillouin light scattering [2] and using spin-polarized electron microscopy [3]. In this study, we propose a simple method of measuring DMI by using the Bragg magneto-optical Kerr effect (MOKE). We observe an asymmetric shift in the hysteresis loop, which is proportional to the strength of iDMI [4]. Here, we utilize Bragg-MOKE in longitudinal mode to which occurs when a broad polarized beam is incident on a periodic array of the magnetic features with size comparable to the wavelength of laser. We have investigated the hysteresis loop shift for 1st and 2nd order of diffraction in off-specular geometry for both patterned graphene (Gr/NiFe(10nm)/Ta) and reference (NiFe(10nm)/Ta). We used triangular pattern (Fig. 1) as proposed in Ref [4]. We found a shift in hysteresis loop for the Gr/NiFe/Ta sample (Fig. 2), which likely due to the presence of iDMI that was previously measured using BLS [2]. Hence, the Bragg-MOKE technique can be a potential technique for rapid quantification of iDMI in magnetic heterostructures. We will also present variable field magnetic force microscopy (MFM) and micromagnetic simulations to support these results.