Microwave Receiving System Based on Cryogenic Sensors for the Optical Big Telescope Alt-Azimuth.

This article presents the results of evaluating the possibility of conducting radio astronomy studies in the windows of atmospheric transparency ~100, ~230, and ~350 GHz using the optical Big Telescope Alt-Azimuthal (BTA) of the Special Astrophysical Observatory of the Russian Academy of Sciences (SAO RAS). A list of some promising astronomical tasks is proposed. The astroclimat conditions at the BTA site and possible optical, cryogenic, and mechanical interfaces for mounting a superconducting radio receiver at the focus of the optical telescope are considered.

Induced electric conductivity in organic polymers.

Poly(diphenylene phthalide) (PDP) belongs to the class of carbocyclic organic electroactive polymers, which exhibits electric conductive properties when an external electric field and/or mechanical stress is applied. In this work, the transport properties of thin-film layered lead-PDP-lead structures were experimentally studied in a wide temperature range. At sufficiently high temperatures, the current voltage characteristics are satisfactorily described in terms of the injection model of currents limited by the space charge.

Electron Spin Resonance of the Interacting Spinon Liquid.

We report experimental verification of the recently predicted collective modes of spinons, stabilized by backscattering interaction, in a model quantum spin chain material. We exploit the unique geometry of uniform Dzyaloshinskii-Moriya interactions in K_{2}CuSO_{4}Br_{2} to measure the interaction-induced splitting between the two components of the electron spin resonance (ESR) response doublet. From that we directly determine the magnitude of the "marginally irrelevant" backscattering interaction between spinons for the first time.

High dynamic resistance elements based on a Josephson junction array.

A chain of superconductor-insulator-superconductor junctions based on Al-AlO -Al nanostructures and fabricated using conventional lift-off lithography techniques was measured at ultra-low temperatures. At zero magnetic field, the low current bias dynamic resistance can reach values of ≈10 Ω. It was demonstrated that the system can provide a decent quality current biasing circuit, enabling the observation of Coulomb blockade and Bloch oscillations in ultra-narrow Ti nanowires associated with the quantum phase-slip effect.

Magnetization and ferromagnetic resonance in a Fe/Gd multilayer: experiment and modelling.

Static and dynamic magnetic properties of a [Fe(35 Å)/Gd(50 Å)] superlattice are investigated experimentally in the temperature range 5-295 K using SQUID magnetometery and the ferromagnetic resonance (FMR) technique at frequencies 7-38 GHz. The obtained magnetization curves and FMR spectra are analysed theoretically using numerical simulation on the basis of the effective field model. At every given temperature, both static and resonance experimental data can be approximated well within the proposed model.

Superconductivity in highly disordered NbN nanowires.

The topic of superconductivity in strongly disordered materials has attracted significant attention. These materials appear to be rather promising for fabrication of various nanoscale devices such as bolometers and transition edge sensors of electromagnetic radiation. The vividly debated subject of intrinsic spatial inhomogeneity responsible for the non-Bardeen-Cooper-Schrieffer relation between the superconducting gap and the pairing potential is crucial both for understanding the fundamental issues of superconductivity in highly disordered superconductors, and for the operation of corresponding nanoelectronic devices.

Formation of the S = 1 paramagnetic centers in the bond-diluted spin-gap magnet.

Electron spin resonance experiment reveals that non-magnetic bond doping of the spin-gap magnet (C4H12N2)Cu2Cl6 (abbreviated PHCC) results in the formation of S  =  1 paramagnetic centers that dominate low-temperature ESR response. We have followed evolution of this signal with doping impurity content and have found that the concentraion of these centers is quadratic over the impurity content. We also observe coexistence of the ESR responses from these local centers and from delocalized triplet excitations over a certain temperature range.

Chiral and collinear ordering in a distorted triangular antiferromagnet.

Magnetization, specific heat, and neutron diffraction measurements are used to map out the entire magnetic phase diagram of KFe(MoO4)2. This stacked triangular antiferromagnet is structurally similar to the famous multiferroic system RbFe(MoO4)2. Because of an additional small crystallographic distortion, it contains two sets of inequivalent distorted magnetic triangular lattices.

Field-controlled phase separation at the impurity-induced magnetic ordering in the spin-Peierls Magnet CuGeO3.

The paramagnetic fraction surviving at the impurity-induced antiferromagnetic phase transition in the spin-Peierls magnet CuGeO3 is found to increase with an external magnetic field. This effect is explained by the competition of the Zeeman interaction and of the exchange interaction of local antiferromagnetic clusters formed on the spin-gap background near impurities.