Normal-state magnetoresistance ofSr2RuO4

Abstract

We report measurements of the in-plane and out-of-plane magnetoresistance (MR) of single crystals of the layered perovskite superconductor ${\mathrm{Sr}}_{2}{\mathrm{RuO}}_{4}$ ${(T}_{c}\ensuremath{\approx}1\mathrm{K}).$ The transverse $c$-axis MR $\ensuremath{\Delta}{\ensuremath{\rho}}_{c}/{\ensuremath{\rho}}_{c}(B)$ $(I\ensuremath{\parallel}c,B\ensuremath{\parallel}ab)$ varies linearly with field at low temperatures consistent with the behavior expected for a quasi-two-dimensional Fermi surface in the intermediate-field regime. $\ensuremath{\Delta}{\ensuremath{\rho}}_{c}/{\ensuremath{\rho}}_{c}(T)$ shows a striking temperature dependence which arises from the competing effects of two separate MR contributions. At low temperatures, $\ensuremath{\Delta}{\ensuremath{\rho}}_{c}/{\ensuremath{\rho}}_{c}$ is large and positive due to the orbital magnetoresistance of the carriers. At high temperatures, however, $\ensuremath{\Delta}{\ensuremath{\rho}}_{c}/{\ensuremath{\rho}}_{c}$ is dominated by a negative MR term that is associated with the nonmetallic out-of-plane resistivity ${\ensuremath{\rho}}_{c}(T).$ We argue that the two contributions to $\ensuremath{\Delta}{\ensuremath{\rho}}_{c}/{\ensuremath{\rho}}_{c}(B,T)$ originate from separate conduction channels along the $c$ axis and that the competition between the metallic and nonmetallic channels is responsible for the unusual temperature dependence of ${\ensuremath{\rho}}_{c}(T).$ Finally, we discuss the relevance of these findings to our current understanding of the unusual magnetoresistance of the high-${T}_{c}$ cuprates.