Temperature dependence performances of fully integrated DC SQUID magnetometers

Temperature dependence of the main characteristics of integrated dc superconducting quantum interference device magnetometers based on niobium technology including an additional positive feedback circuit is reported. Temperatures above 4.2 K have been considered. A nonlinear temperature dependence of the spectral density of the field noise has been observed. The reported measurements show a slow increasing of the field noise up to temperatures of about 5 K, giving a considerable tolerance of the working temperature of niobium magnetometers in some innovative multichannel systems for magnetoencephalography.