Critical currents and scaling laws in sputtered copper molybdenum sulfide

We have measured critical current densities J/sub c/, of superconducting copper molybdenum sulfide prepared by sputtering onto heated sapphire substrates. In addition, we have examined the samples with SEM, TEM, electron microprobe, and x-ray diffraction techniques. Critical currents were measured as a function of external magnetic field and as a function of temperature and sample preparation conditions. We find that a scaling law PP=CB/sup n//sub c2/f(b) describes our results, where P is the pinning force per unit volume, B/sub c2/ is the upper critical field, b is the reduced field bequivalentB.B/sub c2/,f(b) is a function of b only, and C is a constant of proportionality. Our results fit the flux shearing model of Kramer from relatively low b(approx. =0.5) to b=1. Furthermore, applying this model to PbMo/sub 6/S/sub 8/, we estimate the critical current density as a function magnetic field. For examole, we predict J/sub c/> or approx. =10/sup 8/ A/m/sup 2/ at 26 T. From analysis of all experimental data on our samples, we conclude that flux pinning is mainly on excess Mo metal. Th Mo is present as a second phase in the predominantly Chevrel-phase Cu/sub x/Mo/sub 6/S/sub 8/, while all the Cu metal is included in the Chevrel phase.