Time relaxation of microwave second order response of superconductors in   the critical state
  Relaxation of the microwave second order response of YBa2Cu3O7 and Ba0.6K0.4BiO3 crystals in the critical state is studied. The samples are exposed to static and pulsed microwave magnetic fields. The second harmonic signals decay during the time in which the microwave pulse endures. The decay times depend on the supercon-ductor investigated and on the way the value of the static field has been reached. 
A. Agliolo Gallitto, M. Guccione, and M. Li Vigni