The temperature T and magnetic field H dependence of the resistivity $\rho$ has been measured for ${\mathrm{La}}_{0.8-y}{\mathrm{Sr}}_{0.2}{\mathrm{MnO}}_3$ $(y=0\mathrm{}$ and 0.128) films grown on (100) ${\mathrm{SrTiO}}_3$ substrates. The low-temperature $\rho$ in the ferromagnetic metallic region follows well $\rho \mathrm{}(H,T)={\rho }_0\mathrm{}\left(H\right)+A\left(H\right)\mathrm{}{\omega }_s/\sinh (ħ{\omega }_s{/2k}_B{T)+B(H)T}^{7/2}$ with ${\rho }_0$ being the residual resistivity. We attribute the second and third term to small-polaron and spin-wave scattering, respectively. Our analysis based on these scattering mechanisms also gives the observed difference between the metal-insulator transition temperatures of the films studied. Transport measurements in applied magnetic field further indicate that spin-wave scattering is a key transport mechanism at low temperatures.

• Received 1 November 2002

DOI:https://doi.org/10.1103/PhysRevB.67.134405