Electron-phonon scattering times in crystalline disordered titanium alloys between 3 and 15 K

Abstract

We have successfully fabricated bulk crystalline disordered titanium alloys (Ti1-xSnx, T1-xGex, and Ti0.97-xSn0.03Scx) with nominal concentration x of the order of a few at. %. The impurity atoms are gradually introduced into a titanium host to tune the degree of disorder, resulting in residual resistivities rho(0) varying from approximate to 40 to 160 mu Omega cm (corresponding to values of k(F)l approximate to 5-20, with k(F) being the Fermi wave number and l being the electron elastic mean free path). With this wide range of experimentally accessible rho(0), we are able to perform systematic studies of the disorder rho(0), or electron elastic mean free path l, behavior of the electron-phonon scattering time tau(ph). We have measured the magnetoresistivities of these alloys between 3 and 15 K, and compared our results with weak-localization theoretical predictions to extract tau(ph)(T,l) Unexpectedly, we obtain a rather diversified temperature dependence and disorder dependence of tau(ph) as follows. (a) In Ti1-xSnx alloys with rho(0) greater than or similar to 100 mu Omega cm we find 1/tau(ph)similar to T-2/l. (b) In Ti1-xSnx alloys with rho(0) less than or similar to 70 mu Omega cm we find 1/tau(ph)similar to T-3/l. (c) In Ti1-xGex alloys with 50 less than or similar to p(0) less than or similar to 130 mu Omega cm we find 1/tau(ph)similar to T-3 in some alloys and 1/tau(ph)similar to T-4 in others, while at a given temperature 1/tau(ph) is essentially independent of disorder. (d) In Ti0.97-xSn0.03Scx alloys with 55 less than or similar to rho(0) less than or similar to 75 mu Omega cm we obtain 1/tau(ph)similar to T-2. These experimental observations altogether imply that electron-phonon interactions in the presence of strong impurity scattering are very sensitive to the local material environment (the microscopic quality) of a particular sample system, which might be variously modulated with the doping of different kinds of impurity atoms. Our results are compared with existing theoretical predictions for electron-phonon scattering in disordered conductors.