Noise properties and epitaxial quality in low-noise integrated $YBa2Cu3O7$ magnetometers Available to Purchase

Temperature dependent flux-locked loop noise measurements have been performed on low-noise integrated multiloop pickup coil magnetometers using ramp-type Josephson junctions with $PrBa2Cu3O7$ barriers. We show that the noise properties of such multilayer devices depend on the epitaxy of the $YBa2Cu3O7$ top film as analyzed by micro-Raman spectroscopy. At high epitaxial film quality the low-frequency noise is dominated solely by fluctuations of the critical currents of the Josephson junctions and is suppressible by additional bias-current modulation. The noise and the epitaxial properties of different samples are correlated to details in the laser-deposition process of the insulating $SrTiO3$ layer.