Magnetic switching of FSF bridges at low temperatures

The voltage–current characteristics of planar Pd$_{0.99}$Fe$_{0.01}$–Nb–Pd$_{0.99}$Fe$_{0.01}$ microbridges at temperatures significantly lower than the critical one are studied experimentally. It has been found that a magnetic memory effect, which is manifested in the dependence of the shape of the voltage–current characteristics on the mutual orientation of the magnetizations of the F layers, is observed even at such low temperatures. It has been shown that the studied sample can serve as a magnetic switch with a voltage distinction of more than 600 $\mu$V, which corresponds to a characteristic frequency of about $300$ GHz if such bridges are used as memory elements in rapid single-flux quantum logic devices. These characteristics are obtained at a temperature of $0.93T_c$, which is the minimum operating temperature of the implemented memory element. A low-voltage mode of operation of the sample is discovered, characterized by a wide range of permissible bias currents.