Magnetoresistance of disordered ultrathin Pt wires

Abstract

We have measured the transverse magnetoresistance of heavily disordered ultrathin drawn Pt wires which show an unusually large low-temperature resistance increase in zero magnetic field $\frac{\ensuremath{\delta}R(T)}{R\ensuremath{\sim}{10}^{\ensuremath{-}3}\ensuremath{-}{10}^{\ensuremath{-}2}}$ at 1.5 K. An anomalous positive magnetoresistance $\frac{\ensuremath{\delta}R(H)}{R\ensuremath{\sim}{10}^{\ensuremath{-}4}\ensuremath{-}{10}^{\ensuremath{-}3}}$ is observed at moderate fields $H\ensuremath{\le}25$ kG at liquid-He temperatures in high-resistivity ($\ensuremath{\rho}>50$ \ensuremath{\mu}\ensuremath{\Omega} cm) wires. The magnitude of $\frac{\ensuremath{\delta}R(H)}{R}$ increases with resistivity, opposite to Kohler's rule, and increases at lower temperatures where $\ensuremath{\rho}$ remains essentially constant. No additional features in $\frac{\ensuremath{\delta}R(H)}{R}$ are observed to very high fields $H=140$ kG. Neither one- nor three-dimensional effects of electronic localization or interaction can account for both the magnetoresistance $\frac{\ensuremath{\delta}R(H)}{R}$ and the low-temperature resistance increase $\frac{\ensuremath{\delta}R(T)}{R}$.