title: Anisotropic spin relaxation in graphene.
abstract: Spin relaxation in graphene is investigated in electrical graphene spin valve devices in the nonlocal geometry. Ferromagnetic electrodes with in-plane magnetizations inject spins parallel to the graphene layer. They are subject to Hanle spin precession under a magnetic field B applied perpendicular to the graphene layer. Fields above 1.5 T force the magnetization direction of the ferromagnetic contacts to align to the field, allowing injection of spins perpendicular to the graphene plane. A comparison of the spin signals at B=0 and B=2 T shows a 20% decrease in spin relaxation time for spins perpendicular to the graphene layer compared to spins parallel to the layer. We analyze the results in terms of the different strengths of the spin-orbit effective fields in the in-plane and out-of-plane directions and discuss the role of the Elliott-Yafet and Dyakonov-Perel mechanisms for spin relaxation.
authors.affiliation: Physics of Nanodevices, Nijenborgh 4, 9747 AG Groningen, The Netherlands.
authors.forename: N
authors.initials: N
authors.lastname: Tombros
authors.forename: S
authors.initials: S
authors.lastname: Tanabe
authors.forename: A
authors.initials: A
authors.lastname: Veligura
authors.forename: C
authors.initials: C
authors.lastname: Jozsa
authors.forename: M
authors.initials: M
authors.lastname: Popinciuc
authors.forename: H T
authors.initials: HT
authors.lastname: Jonkman
authors.forename: B J
authors.initials: BJ
authors.lastname: van Wees