▎ 摘　　要

We report a spin valve with a few-layer graphene flake bridging highly spin-polarized La0.67Sr0.33MnO3 electrodes, whose surfaces are kept clean during lithographic definition. Sharp magnetic switching is verified using photoemission electron microscopy with x-ray magnetic circular dichroism contrast. A naturally occurring high interfacial resistance similar to 12 M Omega facilitates spin injection, and a large resistive switching (0.8 M Omega at 10 K) implies a 70-130 mu m spin diffusion length that exceeds previous values obtained with sharp-switching electrodes.