Normal State Magnetoresistance of Sr₂RuO₄

We report measurements of the in-plane and out-of-plane magnetoresistance (MR) of single crystals of the layered perovskite superconductor Sr2RuO4 (T-c approximate to 1 K) The transverse c-axis MR Delta rho(c)/rho(c)(B) (I parallel to c,B parallel to 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. Delta rho(c)/rho(c)(T) shows a striking temperature dependence which arises from the competing effects of two separate MR contributions. At low temperatures, ap,lp, is large and positive due to the orbital magnetoresistance of the carriers. At high temperatures, however, Delta rho(c)/rho(c) is dominated by a negative MR term that is associated with the nonmetallic out-of-plane resistivity p(c)(T). We argue that the two contributions to Delta rho(c)/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 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.