Peak effect in hydrogenated ReCr amorphous alloys

Pinning of flux line lattice has been studied in hydrogenated amorphous superconducting Re94Cr6 alloys at different hydrogen contents. Resistivity measurements in magnetic field were made. A change of pinning mechanism was observed from single to collective pinning, depending on the hydrogen content. A sharp peak of the volume pinning force was observed in the vicinity of the critical magnetic field, and explained as a result of the abrupt change in the state of the vortex lattice close to the defects.