Influence of nonuniform critical current density profile on magnetic field behavior of AC susceptibility in 2D Josephson junction arrays (original) (raw)
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Journal of Experimental and Theoretical Physics Letters, 2004
By improving resolution of home-made mutual-inductance measurements technique, a pronounced step-like structure (with the number of steps n = 4 for all AC fields) has been observed in the temperature dependence of AC susceptibility in artificially prepared two-dimensional Josephson Junction Arrays (2D-JJA) of unshunted N b − AlOx − N b junctions with βL(4.2K) = 30. Using a single-plaquette approximation of the overdamped 2D-JJA model, we were able to successfully fit our data assuming that steps are related to the geometric properties of the plaquette. The number of steps n corresponds to the number of flux quanta that can be screened by the maximum critical current of the junctions. The steps are predicted to manifest themselves in arrays with the inductance related parameter βL(T ) matching a "quantization" condition βL(0) = 2π(n + 1).
Josephson junction arrays (JJA) have been actively studied for decades. However, they continue to contribute to a wide variety of intriguing and peculiar phenomena. To name just a few recent examples, it suffice to mention the so-called paramagnetic Meissner effect and related reentrant temperature behavior of AC susceptibility, observed both in artificially prepared JJA and granular superconductors. Employing mutual-inductance measurements and using a high-sensitive home-made bridge, we have thoroughly investigated the temperature and magnetic field dependence of complex AC susceptibility of artificially prepared highly ordered (periodic) two-dimensional Josephson junction arrays (2D-JJA) of both shunted
Reentrant ac Magnetic Susceptibility in Josephson-Junction Arrays
Physical Review Letters, 1997
The paramagnetic Meissner effect ͑PME͒ measured in high-T C granular superconductors has been attributed to the presence of junctions between the grains. Here we present measurements of complex ac magnetic susceptibility from two-dimensional arrays of conventional ͑non-͒ Nb/Al/AlOx/Nb Josephson junctions. We measured the susceptibility as a function of the temperature T, the ac amplitude of the excitation field h ac and the external magnetic field H dc. The experiments show a strong paramagnetic contribution from the multijunction loops, which manifests itself as a reentrant screening at low temperature, for values of h ac higher than 50 mOe. A highly simplified model, based on a single loop containing four junctions, accounts for this paramagnetic contribution and the range of parameters in which it appears. This model offers an alternative explanation of PME that does not involve junctions. ͓S0163-1829͑99͒02234-1͔
By employing mutual-inductance technique and using a high-sensitive bridge, we have thoroughly investigated (both experimentally and theoretically) the temperature and magnetic field dependence of complex AC susceptibility of artificially prepared highly ordered (periodic) two-dimensional Josephson junction arrays (2D-JJA) of both shunted and unshunted Nb-based tunnel junctions as well as disordered three-dimensional arrays (3D-JJA). This paper reviews some of our latest results regarding the influence of non-uniform critical current density profile on magnetic field behavior of AC susceptibility in 2D-JJA, and the origin of remanent magnetization in disordered 3D-JJAs.
Novel magnetoinductance effects in Josephson junction arrays: A single-plaquette approximation
Physics Letters A - PHYS LETT A, 2008
Using a single-plaquette approximation, novel magnetoinductance effects in Josephson junction arrays (JJAs) are predicted, including the appearance of steps in the temperature behavior of magnetic susceptibility. The number of steps (as well as their size) is controlled by the kinetic inductance of the plaquette whose field dependence is governed by the Abrikosov vortices penetrating superconducting regions of the array. The experimental conditions under which the predicted effects should manifest themselves in artificially prepared JJAs are discussed.
Journal of Applied Physics, 1996
Explicit analytic expressions for the lobe structures of the critical current versus magnetic field are provided for small arbitrarily shaped four-sided Josephson junctions. The orientation of the external parallel magnetic field, in the plane of the junction, is also arbitrary. Several configurations worth noting are considered in detail for rhomboid, triangle, parallelogram, and trapezium junctions, once the dependence from the normalized magnetic field has been introduced.
Physical review, 1999
The paramagnetic Meissner effect ͑PME͒ measured in high-T C granular superconductors has been attributed to the presence of junctions between the grains. Here we present measurements of complex ac magnetic susceptibility from two-dimensional arrays of conventional ͑non-͒ Nb/Al/AlOx/Nb Josephson junctions. We measured the susceptibility as a function of the temperature T, the ac amplitude of the excitation field h ac and the external magnetic field H dc. The experiments show a strong paramagnetic contribution from the multijunction loops, which manifests itself as a reentrant screening at low temperature, for values of h ac higher than 50 mOe. A highly simplified model, based on a single loop containing four junctions, accounts for this paramagnetic contribution and the range of parameters in which it appears. This model offers an alternative explanation of PME that does not involve junctions. ͓S0163-1829͑99͒02234-1͔
New Developments in Josephson Junctions Research
DC magnetic moments of SIS and SNS type Josephson 1 junction arrays E.V. Matizen and S.M. Ishikaev Experimental and theoretical study on 2D ordered and 25 3D disordered SIS type arrays of Josephson junctions F.M. Araujo-Moreira and S. Sergeenkov Magnetization states in annular π-junction arrays 45 G. Rotoli Josephson junction as a prototype for synchronization 83 of nonlinear oscillators G. Filatrella