Further Ultrasonic Experiments in Superconducting Polycrystalline Tin

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Abstract
The effect of a longitudinal magnetic field on the sound absorption in a polycrystalline tin rod below and just above the superconducting transition has been studied. When the specimen is left with a frozen-in moment, the shape of the acoustic hysteresis loop is found to vary with change of path of the sound through the specimen. A reasonable qualitative explanation of this effect is given, but there is a shortage of information on other comparable phenomena in a rod of this shape and size; it does seem probable though that the core of the specimen remains largely normal in the intermediate state until an appreciable reverse field produces an escape of trapped flux.