Critical current densities of magnetron sputtered Nb3Ge films

Nb3Ge films fabricated by magnetron sputtering at substrate temperatures Ts, from 600 to 850°C and film thicknesses of 1 -5 μm have been analyzed with respect to transition temperature Tc, critical current density as a function of applied field Jc(H), and grain size. Jcat 5Tesla shows a strong dependence on Ts, decreasing by more than an order of magnitude as Tsincreases from 700 to 815°C. This decrease will be related to grain diameter D. Results will be presented which suggest a lower Jc(H) in thicker films prepared at a fixed Tsis caused by increased grain diameters as the films grow in thickness. Evidence will be presented showing these results to be consistent with grain boundaries being the dominant pinning mechanism in these films.