Electronic density of states in amorphous zirconium alloys

Abstract

We have produced amorphous Zr-Rh, Zr-Ru, and Zr-Re films by means of rf diode cosputtering techniques. Measurements were made of the superconducting transition temperature $T_c$, the normal resistivity $\rho$, and upper critical field $H_{c2\mathrm{}}$. From $\rho$ and ${\left(\frac{d{H}_{c2\mathrm{}}}{\mathrm{dT}}\right)}_{T_c}$ we determined the dressed density of states at the Fermi level $N^{*}=N(1+\lambda )$, where $\lambda$ is the electron-phonon coupling constant and $N$ is the bare density of states. For Zr-Rh and Zr-Re, $N^{*}$ exhibited an approximately linear decrease as the Zr fraction decreased. For Zr-Ru alloys the behavior was more complex. Estimating $N$ for Zr-Rh alloys, we find it to be approximately the same in magnitude and composition dependence as the $N$ for Zr-Cu alloys. We calculate the magnitude and composition dependence of $N$ for Zr-Rh and Zr-Cu alloys with the use of a simple model and obtain good agreement with the experimental results.