## Superconducting flux-flow type ultrasensitive magnetic sensors    [PDF]

Roberto Monaco
Based on recent works[1-3], with this note I present a new class of superconducting ultrasensitive wideband high-dynamics magnetometers based on the magnetic field dependence of the Eck step voltage in long Josephson tunnel junctions (LJTJs). The sensor principle is to capture the flux related to the field to be measured by means of a superconducting loop, perpendicular to the applied field. Then a shielding current circulates in the loop to conserve the flux. If this loop has a narrow constriction, the circulating current density will become relatively high and will locally create a magnetic field large enough to bring a biased LJTJ in the flux flow state, i.e., at a finite voltage. It turned out that the performances of such sensor, among which a magnetic spectral density $S_B^{1/2}= O(fT/\sqrt{Hz})$, despite its simplicity, are comparable to those of the best present-day dc-SQUIDs.
View original: http://arxiv.org/abs/1304.5761