Flux pinning by precipitates

Measurements of pinning forces in two model system superconductors containing either incoherent normal-conducting or coherent superconducting precipitates are reported. An analysis of the bulk pinning forces shows that in both cases the statistical summation of basic interaction forces is appropriate. Furthermore, from the magnitude and the temperature dependence of these basic interaction forces we conclude that in both systems the core pinning interaction, i.e. the gain of condensation energy upon moving the flux line core onto the precipitate, is responsible for pinning. (author)