title: Determination of the spin-lifetime anisotropy in graphene using oblique spin precession.
abstract: We determine the spin-lifetime anisotropy of spin-polarized carriers in graphene. In contrast to prior approaches, our method does not require large out-of-plane magnetic fields and thus it is reliable for both low- and high-carrier densities. We first determine the in-plane spin lifetime by conventional spin precession measurements with magnetic fields perpendicular to the graphene plane. Then, to evaluate the out-of-plane spin lifetime, we implement spin precession measurements under oblique magnetic fields that generate an out-of-plane spin population. We find that the spin-lifetime anisotropy of graphene on silicon oxide is independent of carrier density and temperature down to 150 K, and much weaker than previously reported. Indeed, within the experimental uncertainty, the spin relaxation is isotropic. Altogether with the gate dependence of the spin lifetime, this indicates that the spin relaxation is driven by magnetic impurities or random spin-orbit or gauge fields.
authors.affiliation: Catalan Institute of Nanoscience and Nanotechnology (ICN2), CSIC and The Barcelona Institute of Science and Technology, Campus UAB, Barcelona 08193, Spain.
authors.forename: Bart
authors.initials: B
authors.lastname: Raes
authors.affiliation: INPAC-Institute for Nanoscale Physics and Chemistry, Department of Physics and Astronomy, KU Leuven, Celestijnenlaan 200D, B-3001 Leuven, Belgium.
authors.forename: Jeroen E
authors.initials: JE
authors.lastname: Scheerder
authors.affiliation: Catalan Institute of Nanoscience and Nanotechnology (ICN2), CSIC and The Barcelona Institute of Science and Technology, Campus UAB, Barcelona 08193, Spain.
authors.forename: Marius V
authors.initials: MV
authors.lastname: Costache
authors.affiliation: Catalan Institute of Nanoscience and Nanotechnology (ICN2), CSIC and The Barcelona Institute of Science and Technology, Campus UAB, Barcelona 08193, Spain.
authors.forename: Frédéric
authors.initials: F
authors.lastname: Bonell
authors.affiliation: Catalan Institute of Nanoscience and Nanotechnology (ICN2), CSIC and The Barcelona Institute of Science and Technology, Campus UAB, Barcelona 08193, Spain.
authors.forename: Juan F
authors.initials: JF
authors.lastname: Sierra
authors.affiliation: Catalan Institute of Nanoscience and Nanotechnology (ICN2), CSIC and The Barcelona Institute of Science and Technology, Campus UAB, Barcelona 08193, Spain.
authors.forename: Jo
authors.initials: J
authors.lastname: Cuppens
authors.affiliation: INPAC-Institute for Nanoscale Physics and Chemistry, Department of Physics and Astronomy, KU Leuven, Celestijnenlaan 200D, B-3001 Leuven, Belgium.
authors.forename: Joris
authors.initials: J
authors.lastname: Van de Vondel
authors.affiliation: Catalan Institute of Nanoscience and Nanotechnology (ICN2), CSIC and The Barcelona Institute of Science and Technology, Campus UAB, Barcelona 08193, Spain.|Institució Catalana de Recerca i Estudis Avançats (ICREA), Barcelona 08070, Spain.
authors.forename: Sergio O
authors.initials: SO
authors.lastname: Valenzuela