A resonant method based on a tunnel-diode oscillator (TDO) for precisionmeasurements of relative impedance changes in materials, is described. Thesystem consists of an effective self-resonant LC-tank circuit driven by aforward-biased tunnel diode operating in its negative resistance region.Samples under investigation are placed in the core of an inductive coil andimpedance changes are determined directly from the measured shift in resonancefrequency. A customized low temperature insert is used to integrate thisexperiment with a commercial Model 6000 Physical Property Measurement System(Quantum Design). Test measurements on a manganese-based perovskite sampleexhibiting colossal magneto-resistance (CMR) indicate that this method is wellsuited to study the magneto-impedance in these materials.
展开▼
