An anomalous Hall effect in edge-bonded monolayer graphene.

An anomalous Hall effect (AHE) is usually presumed to be absent in pristine graphene due to its diamagnetism. In this work, we report that a gate-tunable Hall resistance R _xy can be obtained in edge-bonded monolayer graphene without an external magnetic field. In a perpendicular magnetic field, R _xy consists of a sum of two terms: one from the ordinary Hall effect and the other from the AHE ( R _AHE ). Plateaus of R _xy ∼ 0.94 h /3 e ² and R _AHE ∼ 0.88 h /3 e ² have been observed while the longitudinal resistance R _xx decreases at a temperature of 2 K, which are indications of the quantum version of the AHE. At a temperature of 300 K, R _xx shows a positive, giant magnetoresistance of ∼177% and R _AHE still has a value of ∼400 Ω. These observations indicate the existence of a long-range ferromagnetic order in pristine graphene, which may lead to new applications in pure carbon-based spintronics.