Microtorquemeter for magnetization measurements on small superconducting samples

Abstract
A torquemeter with a noise level of ∼10−12 N m was developed and used for magnetization measurements (due to the Meissner–Ochsenfeld effect) on superconducting samples with a mass typically smaller than 10μg. The torquemeter consists of a very soft, thin metal beam, symmetrically placed between two capacitor plates, which are used for position measurement. Due to the symmetric setup electrostatic forces on the beam are largely compensated. A cheap but accurate electronic device replaces the conventional capacitance bridge and lock‐in amplifier. Calibration of this kind of apparatus is discussed in some detail. Experiments are reported on a 6 μg lead disk and on small crystals of YBa2Cu3O7 and Nd2−xCexCuO4−δ.

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