Absence of hyperfine effects in C-13-graphene spin-valve devices

作者：Wojtaszek M^*; Vera Marun I J; Whiteway E; Hilke M; van Wees B J

来源：Physical Review B, 2014, 89(3): 035417.

DOI：10.1103/PhysRevB.89.035417

The carbon isotope C-13, in contrast to C-12, possesses a nuclear magnetic moment and can induce electron spin dephasing in graphene. This effect is usually neglected due to the low abundance of C-13 in natural carbon allotropes (similar to 1%). Chemical vapor deposition (CVD) allows for artificial synthesis of graphene solely from a C-13 precursor, potentially amplifying the influence of the nuclear magnetic moments. In this work we study the effect of hyperfine interactions in pure C-13-graphene on its spin transport properties. Using Hanle precession measurements we determine the spin relaxation time and observe a weak increase of tau(s) with doping and a weak change of tau(s) with temperature, as in natural graphene. For comparison we study spin transport in pure C-12-graphene, also synthesized by CVD, and observe similar spin relaxation properties. As the signatures of hyperfine effects can be better resolved in oblique spin-valve and Hanle configurations, we use finite-element modeling to emulate oblique signals in the presence of a hyperfine magnetic field for typical graphene properties. Unlike in the case of GaAs, hyperfine interactions with C-13 nuclei influence electron spin transport only very weakly, even for a fully polarized nuclear system. Also, in the measurements of the oblique spin-valve and Hanle effects no hyperfine features could be resolved. This work experimentally confirms the weak character of hyperfine interactions and the negligible role of C-13 atoms in the spin dephasing processes in graphene.

• 出版日期2014-1-14
• 单位McGill