Generation of coherent electromagnetic radiation by superconducting films at liquid-nitrogen temperatures

Generation of coherent electromagnetic radiation by GdBa$_2$Cu$_3$O$_{7-x}$ superconducting films is observed in the frequency range $1$–$10$ MHz at the temperature of boiling liquid nitrogen. The generation is caused by the feedback synchronization of the jumps of Abrikosov vortices produced by a low-frequency external magnetic field. This offers new possibilities for the application of high-$T_c$ superconductors in superconducting electronics.