Magnetization and dissipation measurements in the quantum Hall regime using an integrated micromechanical magnetometer

We present low-temperature (365 mK) magnetization measurements of 40x100 mu m(2) mesas of two dimensional electron gases (2DEGs) integrated into micromechanical cantilever magnetometers. Over a wide range of applied magnetic field, the cantilever resonance frequency reveals the thermodynamic magnetization of the 2DEG. Upon illumination of the sample, we observe the appearance of both cyclotron and Zeeman gaps in the density of states. We attribute this to the narrowing of the disorder-broadened Landau levels as the carrier concentration is increased. Additionally, we observe strong peaks in the dissipation of the system at small integer filling factors which we associate with eddy currents excited by the cantilever motion. (C) 2000 American Institute of Physics. [S0021-8979(00)36908-0].