Protecting nickel with graphene spin-filtering membranes: A single layer is enough

Abstract

We report on the demonstration of ferromagnetic spin injectors for spintronics which are protected against oxidation through passivation by a single layer of graphene. The graphene monolayer is directly grown by catalytic chemical vapor deposition on pre-patterned nickel electrodes. X-ray photoelectron spectroscopy reveals that even with its monoatomic thickness, monolayer graphene still efficiently protects spin sources against oxidation in ambient air. The resulting single layer passivated electrodes are integrated into spin valves and demonstrated to act as spin polarizers. Strikingly, the atom-thick graphene layer is shown to be sufficient to induce a characteristic spin filtering effect evidenced through the sign reversal of the measured magnetoresistance.We acknowledge the Helmholtz-Zentrum-Berlin Electron storage ring BESSY II for provision of synchrotron radiation at the ISISS beamline and we thank the BESSY staff for continuous support of our experiments. R.S.W. acknowledges a Research Fellowship from St. John’s College, Cambridge. S.H. acknowledges funding from ERC grant InsituNANO (No. 279342) and EPSRC grant GRAPHTED (EP/K016636/1). P.S. acknowledges the Institut Universitaire de France for a junior fellowship. This research was partially supported by the EU FP7 Work Programme under Grant GRAFOL (No. 285275) and Graphene Flagship (No. 604391).This is the final published version. It first appeared at http://scitation.aip.org/content/aip/journal/apl/107/1/10.1063/1.4923401