Tl_(2)Ba_(2)CaCu_(2)O_(x) Bicrystal Junction DC-SQUID Magnetometers Operating in Unshielded Environment

We fabricated direct-current superconducting quantum interference device magnetometers with single layer epi-taxial Tl_(2)Ba_(2)CaCu_(2)O_(x) films on 36.8° SrTiO_(3) bicrystal substrates.The white Aux noise and the field-flux transformation coefficient of the devices are 1.5 × 10^(-5)Φ0/√Hz and 40 nT/Φ0,respectively.The magnetometers can work in unshielded environment.

Characteristics of Off-Chip Millimeter-Wave Radiation from Serial Josephson Junction Arrays

We investigate the self-emissions from serial high-temperature superconductor bicrystal Josephson junction arrays embedded in a quasi-optical resonator.A bicrystal substrate is used as a dielectric resonator antenna,which increases the coupling strength between the junction array and the electromagnetic(EM)wave.Both three-dimension(3D)electromagnetic simulations and experiments are performed.Strong off-chip radiations are measured from the junction array at 78 GHz and 78 K.The proposed method and the experimental results are important for millimeter wave applications in junction arrays.

Coupling of a T12Ba2CaCu2O8 Thin Film Intrinsic Josephson Junction and a Fabry-Perot Resonator

We study the electromagnetic coupling mechanism of a T1_(2)Ba_(2)CaCu_(2)O_(8)(TI-2212)thin film intrinsic Josephson junction to a hemispherical Fabry-Perot resonator.An effective model to analyze coupling mechanism is put forward.The dielectric substrate is used as a dielectric resonator antenna and the Josephson junction,and a superconducting film is used as the feed line to excite a resonance mode inside the dielectric resonator antenna.To confirm this method,two Josephson junction samples with different dimensions of substrate and shapes of superconducting film are fabricated and tested under microwave irradiations.At the same time,numerical simulations of the antenna characteristics and the field distribution of these samples are performed by numerical simulation.The different coupling intensities of the two samples with the Fabry Perot resonator fit well with the numerical simulation results.The proposed model is important for Josephson junctions used in the microwave field.

Influence of Weak Self-Field Effect on Calculated Activation Energy for Superconducting Thin Film

When the applied field Ba=μ0 H_(a)(H_(a)>H_(p))is perpendicular to the surface of a disk-shaped superconducting thin film with the full penetrated field H_(p),the radius R,and the thickness d,a quantitative relation between the average fieldand the magnetization M is described by=μ_(0)[H_(a)+(0.81 d/R)M]for R»d,where the termμ0(0.81 d/R)M also is the average self-field of the film.Combining this relation with the magnetic flux conservation equation and the Arrhenius relation,the effective activation energy is extracted from the experimental magnetization relaxation and the dynamic magnetization relaxation,respectively.

Field and Current Distribution in Superconducting Film Under Partial Field Penetration

Using finite-element analysis in a self-consistent way with the self-field of the current considered for superconducting thin film,the field and current distributions under partial field penetration are calculated based on the field dependent critical current density function.The field penetrated depth is non-linear with the applied field.Due to the limited resolution of the vibrating sample magnetometer(VSM),the full penetrated field measured by VSM may be much smaller than its actual value.