Annealing-induced magnetic moments detected by spin precession measurements in epitaxial graphene on SiC

We present results of nonlocal and three-terminal (3T) spin precession measurements on spin injection devices fabricated on epitaxial graphene on SiC. The measurements were performed before and after an annealing step at 150 ∘C for 15 minutes in vacuum. The values of spin relaxation length Ls and spin relaxation time τs obtained after annealing are reduced by a factor 2 and 4, respectively, compared to those before annealing. An apparent discrepancy between spin diffusion constant Ds and charge diffusion constant Dc can be resolved by investigating the temperature dependence of the g factor, which is consistent with a model for paramagnetic magnetic moments.