Experimental research of longitudinal ultrasound absorption in   intermediate state of high pure type I superconductor
  The experimental research of the longitudinal ultrasound absorption in an intermediate state of the high pure Ga single crystal at the frequencies of 30 - 130 MHz at the temperatures of 0.4 - 0.5 K, using the impulse method, is completed. The new effects in the absorption of ultrasound in an intermediate state of the high pure type I superconductor are discovered. The giant oscillations in the dependence of the ultrasound absorption on the magnetic field at the magnitudes below the critical magnetic field, H < Hc, in an intermediate state of the high pure Ga single crystal are experimentally observed The maximum of the monotonic part of the ultrasound absorption on the magnetic field is also obtained. The additional experimental results in the dependence of the ultrasound absorption on the frequency of longitudinal ultrasonic wave f and on the orientation of external magnetic field are reported. In the case of the high frequencies ultrasonic signal, the different behaviour of the monotonous part of the dependence of the ultrasound absorption on the magnetic field in an intermediate state, comparing to the theoretical prediction [10], is found. The anomalous distinction in the dependence of the ultrasound absorption on the orientation of magnetic field in an intermediate state of Ga in comparison with the dependence of the ultrasound absorption in a normal state of Ga at the same temperature and at the magnitude of magnetic field equal to the critical magnetic field, H = Hc, is observed. The possible theoretical mechanisms to explain the nature of big oscillations in the dependence in an intermediate state of the high pure type I superconductor are proposed. 
Anatoly G. Shepelev, Oleg P. Ledenyov and Genady D. Filimonov
cond-mat.supr-con cond-mat.mtrl-sci physics.ins-det