Low‐frequency noise, electric and magnetic characteristics of Bi‐based thick films in the superconducting temperature region

The low‐frequency noise characteristics in Bi‐based superconductor thick films have been measured as a function of frequency, temperature, bias current, and applied magnetic field. These results have been compared with the resistance, temperature coefficient of the resistance dependences on temperature, and also with ones of Y‐based thick film superconductor. Our investigation shows that the peak of the voltage noise is not related with the peaks both of the temperature coefficient of the resistance and the voltage‐to‐flux transfer function. We suppose that voltage fluctuations are taking place at grain boundaries (weak Josephson links) between superconducting and normal grains, and that depend on the relative filling of the film by the superconducting grains. We represent a model that explains the resistance fluctuation peak in the superconducting transition temperature region.