Unusual heavy-mass nearly ferromagnetic state with a surprisingly large Wilson ratio in the double layered ruthenates (Sr${}_{1-x}$Ca${}_x$)${}_3$Ru${}_2$O${}_7$

Abstract

We report an unusual nearly ferromagnetic, heavy-mass state with a surprisingly large Wilson ratio $R_{\text{w}}$ (e.g., $R_{\text{w}}\sim$ 700 for $x=$ 0.2) in double layered ruthenates (Sr${}_{1-x}$Ca${}_x$)${}_3$Ru${}_2$O${}_7$ with 0.08 $<x<$ 0.4. This state does not evolve into a long-range ferromagnetically ordered state despite considerably strong ferromagnetic correlations, but freezes into a cluster-spin-glass at low temperatures. In addition, evidence of non-Fermi liquid behavior is observed as the spin freezing temperature of the cluster-spin-glass approaches zero near $x\approx$ 0.1. We discuss the origin of this unique magnetic state from the Fermi surface information probed by Hall effect measurements.

4 pages, 4 figures; to be published in Physical Review B Rapid Communication; solve the problem with Fig.1