Measurements of the AC longitudinal resistance of a GaAs-AlGaAs quantum Hall device

The shape of the i = 2 minimum of the ac longitudinal resistance R-x of a q uantum Hall device has been obtained at different frequencies from 160 Hz t o 16 kHz, The frequency dependence of the resistance and the virtual reacta nce! measured at the i = 2 and i = 4 plateau centers with different circuit conditions, have been analyzed, The measurements have been performed with a ner system, which includes dedicated electronic units to maintain close t o zero the voltage at the current measurement terminal of the del-ice and t he current at the voltage terminals, Within the validity of the equivalent circuit adopted to represent the quantum Hall device and the measuring syst em, R-x was found to follow an increasing function of frequency, in agreeme nt with previous investigations.