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High Resolution Hall Measurement across the Phase Separated Metal-Insulator Transition in VO2 Reveals Non-Trivial Relation to Carrier Density
Tony Yamin , Yakov M. Strelniker , Amos Sharoni
Department of Physics and Bar-Ilan Institute of Nanotechnology Advanced Materials Bar Ilan University, Ramat Gan, 5290002, Israel
Hall measurements are usually performed to obtain information about the material mobility and charge carrier density. However, in transition-metal oxides, continuous Hall measurements are quite scarce. We present a continuous Hall measurement across the metal-insulator transition (MIT) in VO2, which undergoes a drastic change in resistance of 4 orders of magnitude around 340K. In the high-resistance regime even small misalignment of the contacts results with a significant offset that screens the Hall signal. Our continuous measurement was possible using the reciprocity relation , that implies that instead of changing field polarity one can simply measure at two different configurations that removes the zero-field offset. Using that switching method we were able to change slowly and continuously the temperature and measure the pure Hall signal along it. The surprising results show a difference of over 1 order of magnitude between resistivity and Hall resistance. Such a change is naively regarded as a change in mobility. We were able to prove by applying the exact relation theory that the mobility is almost constant, and that the discrepancy is due to the VO2 spatial phase separation across the MIT.