Magnetic properties of superconductors studied by neutron depolarization

A new method is described which allows the study of the magnetic properties of superconductors. Measurements on various niobium and lead samples were taken to study the influence of surface conditions and lattice defects on the formation of the mixed and intermediate states. A strong dependence of flux penetration on surface conditions is found. AboveH _C1 the results indicate the formation of a disturbed flux line lattice. The influence of external fields present when the superconductor is cooled throughT _c is discussed and evidence for the intermediate state of type II superconductors is presented. Finally a simple model is used to evaluate the mean angle of deviation from the ideal lattice.