Dislocation resonance in superconducting tin

Ultrasonic attenuation in the superconducting state of strained samples of single crystals of tin shows a strong dependence on the dislocation density. The dislocation density is estimated with the help of a suitable etch pit method. The etch pits are square in shape and exhibit symmetric dislocation lines normal to the (100) planes. The number of etch pits reveals a direct dependence on the physical state of the specimen. The dislocation density estimated by this etch pit method can be related to the extra attenuation Δasub(s), shows a resonant behaviour and the resonance frequency is dependent on the dislocation density. It is also observed that the functional relationship between the resonance frequency and the dislocation density is different in different regions of the dislocation density. (author)