Violation of the Mott-Ioffe-Regel limit:: high-temperature resistivity of itinerant magnets Srn+1RunO3n+l (n=2, 3, ∞) and CaRuO3

Srn+1RunO3n+1 represents a class of layered materials whose physical properties are a strong function of the number of Ru-O layers per unit cell, n. These materials along with the paramagnetic CaRuO3 shares two major characteristics, namely, robust Fermi liquid behavior at low temperatures and anomalous transport behavior featured by linear temperature dependence of resistivity at high temperature. There is no crossover separating such two fundamentally different states. In this paper, we report results of our study that systematically addresses anisotropy and temperature dependence of resistivity as a function of n for the entire Srn+1RunO3n+1 series and CaRuO3 and for a wide temperature range of 1.7 K < T < 900 K. It is found that the anomalous transport behavior correlates with magnetic susceptibility and that the scattering mechanism(s) driving the anomalous transport behavior becomes stronger with reducing dimensionality. (C) 2004 Elsevier Ltd. All rights reserved.