P. Perna
IMDEA NANOSCIENCE, Campus de Cantoblanco, Madrid, Spain
The development of room temperature magnetic devices exploiting Spin Orbit effects is at the forefront of actual research. A major challenge for future spintronics is to develop suitable spin transport channels with superior properties such as long spin lifetime and propagation length. Graphene can meet these requirements, even at room temperature [1]. However, the development of all-graphene spintronic devices requires that, in addition to its passive capability to transmit spins over long distances, other active properties are incorporated to graphene. The generation of long range magnetic order and spin filtering in graphene have been recently achieved by molecular functionalization [2,3] as well as by the introduction of giant spin-orbit coupling (SOC) in the electronic bands of graphene [4]. On the other side, taking advantage of the fast motion of perpendicular magnetic anisotropy (PMA) chiral spin textures, i.e., Néel-type domain walls (DWs) and magnetic skyrmions, can satisfy the demands for high-density data storage, low power consumption and high processing speed [5].
Here, I report on high quality, epitaxial graphene/Co(111)/Pt(111) stacks grown on (111)-oriented insulating oxide crystals, characterized by STM, LEED, STEM, Kerr Magnetometrry and Microscopy, XAS-XMCD, XMRS and SP-ARPES, which exhibit enhanced PMA for Co layers up to 4 nm thick and left-handed Néel-type chiral DWs stabilized by interfacial Dzyaloshinskii-Moriya interaction (DMI) localized at both graphene/Co and Co/Pt interfaces with opposite sign [6]. While the DMI at Co/Pt side is due to the intrinsic SOC [7], the sizeable DMI experimentally found at the Gr/Co interface has Rashba origin [6]. The active magnetic texture is protected by the graphene monolayer and stable at 300 K in air, and, since it is grown on an insulating substrate, amenable to transport measurements.
[2] M. Garnica et al., Long range magnetic order in a purely organic 2D layer adsorbed on epitaxial graphene, Nature Phys. 9, 368–374 (2013).
[3] D. Maccariello, et al., Spatially resolved, site-dependent charge transfer and induced magnetic moment in TCNQ adsorbed on graphene, Chemistry of Materials 26 (9), 2883-2890 (2014).
[4] F. Calleja et al., Spatial variation of a giant spin–orbit effect induces electron confinement in graphene on Pb islands, Nature Physics 11, 43–47 (2015).
[5] A. Fert, V. Cros and J. Sampaio, Skyrmions on the track, Nat. Nanotech. 8, 152–156 (2013).
[6] F. Ajejas, et al., Unravelling Dzyaloshinskii–Moriya interaction and chiral nature of Graphene/Cobalt interface, Nano Lett. 18(9), 5364-5372 (2018).
[7] F. Ajejas, et al., Tuning domain wall velocity with Dzyaloshinskii-Moriya interaction, Appl. Phys. Lett. 111, 202402 (2017).