Resonance-like giant magnetotransport anomaly in GaAs/AlGaAs heterostructures with a single Ni dot

Magnetotransport measurements of two-dimensional electron systems in GaAs/AlGaAs heterostructures with a single Ni dot of micron scale have been done in high magnetic fields up to View the MathML source and at low temperatures between View the MathML source and View the MathML source. We found new resonance-like giant magnetoresistance anomalies in both Rxx and Rxy. These anomalies mainly originate from an anomalous potential drop occurring at a certain part of the sample. Possible origins of the potential anomalies are discussed.