Possible manifestation of spin fluctuations in the temperature behavior of resistivity of Sm$_{1.85}$Ce$_{0.15}$CuO$_4$ thin films

A pronounced step-like (kink) behavior in the temperature dependence of resistivity $\rho (T)$ is observed in the optimally-doped $\mathrm{Sm_{1.85}Ce_{0.15}CuO_4}$ thin films around $T_{sf}=87\,$K and attributed to manifestation of strong spin fluctuations induced by $\mathrm{Sm^{3+}}$ moments with the energy $\hbar\omega_{sf}=k_BT_{sf}\simeq7\,$meV. In addition to fluctuation induced contribution $\rho_{sf}(T)$ due to thermal broadening effects (of the width $\omega_{sf}$), the experimental data are found to be well fitted accounting for residual (zero-temperature) $\rho_{\rm res}$, electron-phonon $\rho_{e-ph}(T)=AT$ and electron-electron $\rho_{e-e}(T)=BT^2$ contributions. The best fits produced $\omega_p=2.1\,$meV, $\tau_0^{-1}=9.5\cdot10^{-14}\,{\rm s}^{-1}$, $\lambda=1.2$, and $E_F=0.2\,$eV for estimates of the plasmon frequency, the impurity scattering rate, electron-phonon coupling constant, and the Fermi energy, respectively.