Mechanism of pinning state destruction in niobium films

Resistive measurements of critical current densities of niobium films prepared by an electron-beam evaporation in vacuum are carried out. The films of different thickness are found to have two types of relation between pinning volume force and reduced magnetic field. The observed effect is caused by a Lorenze force-induced change in the mechanism of pinning state destruction from the 'plastic' to an 'elastic' one with decrease in thickness of the films