Michael Mans

A thin film HTSC-Hall magnetometer––development and application

Abstract We have investigated a thin film Hall sensor coupled with a high- T C superconducting antenna structure. Based on theoretical calculations and on a well developed thin film technology, magnetometers with different layouts were realized on SrTiO 3 and buffered silicon substrates. The best sensors on SrTiO 3 show a sensitivity of 2.4 V/T and a white noise level of 2–3 nV/√Hz at 77 K. Further, we present eddy-current measurements with the hybrid HTSC-Hall magnetometer in a non-destructive evaluation system.

Synchronization of serial intrinsic Josephson junction arrays on vicinal substrates

A resonator together with a resistive shunting cover over the microbridge was applied to synchronize intrinsic Josephson junctions. We made both numerical and experimental investigations of the electrical properties of such microbridges: the multibranch behaviour above critical currents and switching between branches. The stability analyses revealed that in-phase states are sensitive to noise. Optimal parameters for synchronization of the system of two junctions up to 26–27% spread of critical currents are calculated.

Development of a thin-film high-temperature superconductor Hall magnetometer

We have developed and investigated a thin-film Hall sensor coupled with a high-TC superconducting antenna structure. In this paper we present a theoretical model from which we can derivate the criteria for the layout and the technological realization of the sensor system. The model describes the improvement in the sensitivity of the magnetometer system by a superposition of the external field and an inductive incoupling of a field generated from the superconducting antenna. Based on the theoretical results it is possible to realize a hybrid magnetometer with a sensitivity of about 2.3 V T−1 and with a field resolution of about 1 nT Hz−1/2 at a temperature of 77 K.

The Resonant Interaction of Intrinsic Josephson Junctions With Standing Waves

IV-characteristics of shunted microbridges made of Tl2Ba2CaCu2O8 (TBCCO) were measured. The TBCCO films were grown epitaxially on 20° misaligned LaAlO3 substrates and then covered by the gold shunting layer. Each of the microbridges consisted of about 360 shunted intrinsic Josephson junctions. Self-induced resonant particularities with a main period of about 17 mV were found on IV-curves. We showed that these particularities did not depend on the characteristics of the individual junctions and that they were connected with the geometrical dimensions of the system. The origin of particularities was the interaction of Josephson generation with the standing wave appeared in the system. We modeled this interaction considering radiation of junctions into the transmission line and found that the model described the main resonant structure of IV-characteristics. Strong synchronization of junctions appeared in the vicinity of the first particularity.

Coherent radiation in serial arrays of Josephson junctions

We measured IV-characteristics of a planar array of about 362 shunted intrinsic Josephson junctions in microbridges made from the Tl2Ba2CaCu2O8 layers which were grown epitaxially on 20° misaligned LaAlO3 substrates. The IV-characteristics contained resonant particularities (jumps of voltages) with a main period of 17 mV. We showed that the origin of particularities was the interaction of Josephson generation with the internal resonant mode of the system. We modeled this interaction considering the radiation of junctions into the transmission line and found that strong synchronization of junctions appeared in the vicinity of the first particularity. The estimate of the ac power emitted into free space was 0.05-0.1 microwatt, whereas the power of 0.3-0.5 mW was emitted inside the resonant system.