  We demonstrate the anomalous Hall effect (AHE) in single-layer graphene
exchange-coupled to an atomically flat yttrium iron garnet (YIG) ferromagnetic
thin film. The anomalous Hall conductance has magnitude of ~0.09(2e2/h) at low
temperatures and is measurable up to ~ 300 K. Our observations indicate not
only proximity-induced ferromagnetism in graphene/YIG with large exchange
interaction, but also enhanced spin-orbit coupling which is believed to be
inherently weak in ideal graphene. The proximity-induced ferromagnetic order in
graphene can lead to novel transport phenomena such as the quantized AHE which
are potentially useful for spintronics.
