Isotropic spin relaxation in graphene on hexagonal boron nitride

Abstract

We study the spin-lifetime anisotropy of spin-polarized carriers in graphene on top of hexagonal boron nitride (h-BN) using non-local lateral spin-valve devices (Figure 1) with a method that we recently developed. 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 create an out of plane spin population by applying an oblique magnetic field and determine the relaxation of the non-precessing spin component (Figure 2). We find, within the experimental uncertainty, that the spin relaxation in graphene on boron nitride is isotropic, as it was previously found in graphene on SiO2. This result suggests that the substrate effects present on SiO2, which are expected to be absent or suppressed on h-BN, such as roughness, dangling bonds and charge traps, might play a minor role in making the spin relaxation isotropic and, more generally, in the spin relaxation.