Position and amplitude of proximity effect peaks in the magnetization curves of NbTi/Cu and NbTi/CuMn multifilamentary strands

The magnitude and position of proximity-effect-related magnetization peaks in the M-H loops of multifilamentary NbTi superconductive composites have been studied. M-H loops were taken at T=4.2 K as a function of field-sweep amplitude, H_M, for several specimens. Three regimes emerge: (i) low field, where proximity effects are mainly shielding in nature; (ii) high field, where there are anomalous trapping effects: and (iii) an intermediate-field region, corresponding to a crossover between these two regimes. Correlations are made between these regimes and the specimen parameters H_C1,NbTi and H_p,NbTi. A relationship is found between the magnitude of the maximum of the high-field magnetization and the breakdown field of the copper