Experimental Contribution to the Summation Problem of Pinning Forces in Type-II Superconductors

Abstract

The pinning-force density $P_v$ in Nb single crystals containing platelike ${\mathrm{Nb}}_2$N precipitates shows a strong dependence on the orientation of the precipitates with respect to the fluxline direction. Using purely geometrical arguments this anisotropy can be quantitatively explained by assuming that $P_v\propto {K_0}^2$, where $K_0$ is the individual flux-line-defect interaction force. This points to a summation process which is governed by the elastic behavior of the flux lattice.