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$_{7}$

TL;DR

This study uncovers a nearly ferromagnetic, heavy-mass state with an exceptionally large Wilson ratio in double layered ruthenates, which exhibits spin-glass behavior and non-Fermi liquid characteristics near a critical composition.

Contribution

It reveals a novel magnetic state with an enormous Wilson ratio and spin-glass behavior in ruthenates, providing insights into correlated electron phenomena in layered materials.

Findings

Large Wilson ratio (~700 at x=0.2) indicating strong ferromagnetic correlations.

Absence of long-range ferromagnetic order despite strong correlations.

Emergence of non-Fermi liquid behavior near x ≈ 0.1.

Abstract

We report an unusual nearly ferromagnetic, heavy-mass state with a surprisingly large Wilson ratio $R_{\textrm{w}}$ (e.g., $R_{\textrm{w}}\sim$ 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.