▎ 摘　　要

Analogous to the case of classical metal oxide semiconductor field-effect transistors, transport properties of graphene-based devices are determined by scattering from adventitious charged impurities that are invariably present. The presence of charged impurities renders experimental graphene samples "extrinsic" in that their electrical performances also depend on the environment in which graphene operates. While the role of such an extrinsic disorder component has been studied for conventional charge transport in graphene, its impact on the magnetotransport remains unexplored. Here, we show that single-layer graphene transistors with a low density of extrinsic disorder feature a larger magnetoresistance (MR) than those with a high density. Importantly, in gated single-layer devices with a low density of charged impurities, we find that MR peaks at gate voltage values far from the charge neutrality point not only at a low temperature but also at room temperature; in particular, MR approaches 800% at room temperature and 1400% at 50 K in such devices. In addition, dynamic measurements of MR on devices with a low degree of extrinsic disorder lead to stable and reliable single-layer graphene magnetosensors endowed with an ultralow power consumption of 2.5 nW. Our work indicates that the initial value of the minimum conductivity sigma(0) at room temperature along with carrier mobility must be looked at to select the most promising devices for magnetosensing.