High Field Properties of Nb_3Ge and NbN Films(Low-T_c Superconducting Materials Research)

概要

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Sputtered and CVD-prepared films of A15-type Nb_3Ge and sputtered films of B1-type NbN have been studied on their high field properties. Further, strain effects of critical current density J_c have been investigated on NbN. The J_c of sputtered Nb_3Ge films exceeds 1x10^5 A/cm^2 at fields up to 20 T. In CVD-prepared films, the J_c is somewhat lower in fields higher than 20 T and is highly affected by their deposition temperature. The upper critical field B_<c2> of two kinds of films is roughly proportional to their transition temperature T_c. NbN films have anisotropy in B_<c2>, which yields strong anisotropy in J_c with respect to the field orientation. The values of J_c are higher in the perpendicular field to a film plane and reach 1x10^5 A/cm^2 at 21 T. The B_<c2> increases with ρ_n. Little change in J_c has been observed under strains above 1 % at 9 T for NbN films on Hastelloy B tape.
東北大学の論文