Investigation of anomalous thermodynamic and transport properties of Sr$_{1-x}$Ca$_x$RuO$_3$ ($x \geq 0.8$)

TL;DR

This study explores the complex thermodynamic and transport behaviors of Sr$_{1-x}$Ca$_x$RuO$_3$ with high calcium content, revealing both Fermi liquid and non-Fermi liquid regimes, and compares experimental results with theoretical models.

Contribution

The paper provides detailed experimental phase diagrams and demonstrates the applicability of SCR and hidden Fermi liquid theories to describe the observed properties.

Findings

Identification of Landau Fermi liquid and non-Fermi liquid behaviors.

Good agreement of $C/T$ and $ ho(T)$ with SCR theory up to 20 K and 5 K respectively.

Observation of Schottky anomaly due to ferromagnetic clusters in weak magnetic fields.

Abstract

Thermodynamic and transport properties of Sr$_{1-x}$Ca$_x$RuO$_3$ with a calcium concentration $x \geq 0.8$ were investigated at low temperatures and in external magnetic field. The investgations revealed a Landau Fermi liquid (LFL) behaviour characterized by specific heat $C/T = const$ and resistivity $\rho\sim T^2$ and an anomalous non-Fermi liquid (NFL) behaviour with $\rho \sim T^{5/3}$ and a quasi-logarithmic increase of $C/T$ with decreasing temperature. The $T$--$x$ and $T$--$B$ phase diagrams which separate both regions were prepared for the investigated materials. Then, the experimental behaviour of $C/T$ and $\rho(T)$ were compared with predictions of the self-consistent renormalization (SCR) theory of spin fluctuations. Within this approach, $C/T(T)$ was well described up to 20 K. The SCR parameters $y_0$, $y_1$ and $T_0$ inferred from specific heat analysis allowed to describe properly $\rho(T)$ up to approximately 5 K. In addition, the resistivity data were analysed within the `hidden Fermi liquid' theory of Anderson, obtaining very good descritption of the experimental behaviour up to about 25 K. An anomalous increase of the $C/T$ ratio already in the LFL region below 2 K in very weak magnetic fields (0.2--0.3 T) was identified as caused by the Schottky anomaly induced by ferromagnetic clusters embodied into the essentially paramagnetic materials.