We have developed and investigated a thin-film Hall sensor coupled with a high-T C 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.

Different thin Tl 2 Ba 2 CaCu 2 O 8 layers were grown on 20°vicinal cut LaAlO 3 substrates by means of a two-step process. SEM pictures showed that thin film layers with a thickness smaller than 150 nm grow completely in the 20°misalignment given by the substrate but they also show few holes in the films. Thicker layers showed areas of c-axis growth beneath the expected misaligned texture whereas the allotment and numbers of c-axis islands depend on the layer thickness. TEM investigations in the selected area of misaligned growth showed a clear epitaxial relationship between the substrate and the film but they also revealed a domain like growth of the layers with plain Tl 2 Ba 2 CaCu 2 O 8 grains and stacking faults. Furthermore, the films had a rather high surface roughness depending on the layer thickness. Thin films with a thickness of 120 nm were used to pattern micro-and sub-micrometer bridges. Because of the misaligned growth and the high anisotropy of the Tl 2 Ba 2 CaCu 2 O 8 the bridges formed serial arrays of intrinsic Josephson junctions. Electrical measurements on these bridges revealed very complex dynamics within such devices. The current-voltage characteristics showed the well known branch structure of intrinsic Josephson junction arrays but with a statistical distribution of the transition currents from measurement to measurement. The temperature dependencies of the smallest critical currents generally deviated from the Ambegaokar-Baratoff theory. There was no complete suppression of the super current in an effective B-field up to 4.2 T. The analysis of the current-voltage characteristics indicated a collective transition switching especially in the first few transitions. Those could be split up by the application of a magnetic field and by the irradiation of mm-waves but not by an increment of the operation temperature. Furthermore, distinct two level fluctuations and chaotic like behavior were observed.

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.

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