Magnetoresistance in thin palladium-carbon mixture films

We report magnetoresistance measurements on thin granular ${\mathrm{Pd}}_{\mathrm{x}}$ ${\mathrm{C}}_{1\mathrm{-}\mathrm{x}}$ films with various compositions (0.45<x<1) which have been prepared by codeposition of pure palladium and high-purity carbon onto quartz crystal substrates at room temperature. The localization-induced magnetoresistance is found to be positive for all ${\mathrm{Pd}}_{\mathrm{x}}$ ${\mathrm{C}}_{1\mathrm{-}\mathrm{x}}$ films investigated, which gives evidence of the presence of strong spin-orbit coupling. Electron-electron interaction effects on the resistance behavior are also observed, but only in high magnetic fields (B>3 T). The phase-breaking time ${\tau }_{\Phi }$ is obtained from the magnetoresistance measurements for temperatures between 1.7 and 20 K, showing a power-law dependence with p=1 below 5 K and with p=2 above. For temperatures T>20 K the inelastic scattering time ${\tau }_i$ is found to be proportional to $T^{\mathrm{-}3}$ ($T^{\mathrm{-}1}$ at high temperatures) as revealed by the $R_{\square }$(T) behavior of the various ${\mathrm{Pd}}_{\mathrm{x}}$ ${\mathrm{C}}_{1\mathrm{-}\mathrm{x}}$ films. We find that ${\tau }_{\Phi }$ coincides with ${\tau }_i$ at appropriate temperatures, which experimentally proves that ${\tau }_i$(T) is a continuously varying function in the whole temperature range (1.7<T<300 K) investigated. The results are compared with theoretical predictions as well as with recent measurements on pure Pd and Pd-Au films by other authors.