Dynamic and stimulated rf echo in high-Tc superconducting powders

Phonon echo in superconducting MgB 2

“…However, the amplitude does not follow the B 4 0 -dependence theoretically predicted in [10]. In most high-T c superconductors at fields below 0.5-0.7 T the amplitude obeys the B 2 0 law [13,14], but in higher fields the exponent becomes even smaller [15,16]. Most likely, the B 4 0 -dependence is inadequate because it follows from an oversimplified model, which does not take into account the nonlinear properties of the echo.…”

“…A constant external magnetic field for driving and registration of the mechanical vibrations is necessary in this case. When the high-T c superconductors appeared, the acoustic echo was also used [11][12][13][14][15][16][17] for investigations of their superconducting properties, such as superconducting band gap in YBa 2 Cu 3 O 7−δ [11] and YBa 2 Cu 3−x Fe x O 7−δ [17] samples.…”