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We demonstrate that a multiply connected superconducting structure in combination with a perpendicularly magnetized magnetic dot can be used as a current source for superconducting elements and as an external phase shifter. The concept has been tested by measuring the superconducting Tc(B) phase boundary and critical current of an Al superconducting loop placed on the top of a micron-sized Co/Pd magnetic dot. A pronounced asymmetry in the voltage–current characteristic of the loop with respect to the polarity of the external magnetic field, as well as a shift of the Tc(B) phase boundary along the field axis indicate the presence of a persistent current in the loop. [ABSTRACT FROM AUTHOR]

Nucleation of superconductivity and vortex patterns have been studied in mesoscopic samples providing the crossover between square and rectangular geometries. The measured nucleation line,Tc(H), has been analyzed in the framework of the linearized Ginzburg-Landau theory. A very good agreement has been found between the theoreticalTc(H) boundary and the experimental data for rectangles with different aspect ratios. The superconductor/ferromagnet hybrids, such as magnetic Co/Pd dot in a superconducting loop and the dot on top of a superconducting disk have also been investigated. Pronounced effects of the dot on theTc(H) boundary have been found, including strong asymmetry with respect to the field polarity. [ABSTRACT FROM AUTHOR]

Longitudinal and transversal permanent electric fields generated by an ac current through superconducting Pb and Nb thin strips have been studied as the function of the drive frequency (103≤f≤108 Hz), temperature, and magnetic field. At low frequencies (f<104 Hz) and below the critical temperature, the superconducting strips behave as one-dimensional rectifiers, whereas for higher drive frequencies (f>105 Hz) the rectification becomes two dimensional. The rectification strongly depends on the magnetic field, temperature and ac drive. The unusual dc electric field topology generated by the ac current in the superconducting strips can be explained by a local rectification due the oppositely directed asymmetric edge (Bean-Livingston type) barriers [ABSTRACT FROM AUTHOR]

By measuring the critical current versus the applied magnetic field Ic([uppercase_phi_synonym]) of an Al superconducting loop enclosing a soft Permalloy magnetic dot, we demonstrate that it is feasible to design a linear magnetic flux amplifier for applications in superconducting quantum interference devices. The selected dimensions of a single-domain Permalloy dot provide that the preferential orientation of the magnetization is rotated from the perpendicular direction. By increasing an applied magnetic field, the magnetization of the dot coherently rotates toward the out-of-plane direction, thus providing a flux gain and an enhancement of the sensitivity. As a result of a pronounced shape anisotropy, the flux gain generated by the dot can be tuned by adjusting the dimensions of the dot. [ABSTRACT FROM AUTHOR]

We have studied electromagnetic flux guidance and confinement effects in NiFe cores, interconnecting three Al rings, to form a mesoscopic transformer-like device. Applying ac signals (of low amplitude and kHz frequency) to the contact pads of a semiclosed ring induced time-varying magnetic fields, which could be transferred to a nearby, closed ring, via the aid of a NiFe core. Similarly, a second core carried the fields of this ring, resulting from the induced signals, over to a third, semiclosed ring where readouts were performed over an applied load, using a lock-in amplifier. Highly linear curves of output versus input signal at stable phase were obtained with effective mutual inductance in the μH regime, giving an improvement of the order of 106 on the free field. [ABSTRACT FROM AUTHOR]