Heavy-Electron Behavior and Structural Change in Ca1.7Sr0.3RuO4

R. Jin; J. R. Thompson; J. He; J. M. Farmer; N. Lowhorn; G. A. Lamberton,; T. M. Tritt; D. Mandrus

paper

Heavy-Electron Behavior and Structural Change in Ca1.7Sr0.3RuO4

arXiv:cond-mat/0112405

Abstract

Sr $_{2}$ RuO $_{4}$ is an unconventional superconductor with a tetragonal structure, whereas Ca $_{2}$ RuO $_{4}$ is a Mott insulator with orthorhombic symmetry. The substituted Ca $_{2 - x}$ Sr $_{x}$ RuO $_{4}$ has yielded a rich phase diagram that is just beginning to be explored in detail. Experimental investigation of the resistivity $ρ$ , susceptibility $χ$ , specific heat C $_{p}$ , Hall coefficient R $_{H}$ , and X-ray diffraction of Ca $_{1.7}$ Sr $_{0.3}$ RuO $_{4}$ reveals a structural phase transition near T $_{0}$ = 190 K and heavy-Fermion (HF) behavior below a coherence temperature T $^{*}$ $\sim$ 10 K, resembling that of the $f$ -electron HF compound UPt $_{3}$ . The observation of T $^{2}$ -dependence of $ρ$ below $\sim$ 0.5 K suggests a Fermi-liquid ground state. Based upon our data and theoretical calculations, we argue that the structural change at T $_{0}$ may be responsible for the formation of the HF state.

5 pages, 1 table, 4 figures

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