Investigation of the ferromagnetic transition in the correlated 4d perovskites SrRu$_{1-x}$Rh$_x$O$_3$

TL;DR

This study investigates how substituting Rh for Ru in SrRuO$_3$ affects ferromagnetism and electronic properties, revealing a gradual suppression of ferromagnetic order and unusual specific heat behavior near critical compositions.

Contribution

It provides a comprehensive experimental analysis of the magnetic and electronic phase transitions in SrRu$_{1-x}$Rh$_x$O$_3$, highlighting novel anomalies near critical Rh concentrations.

Findings

Ferromagnetic order vanishes at x ~ 0.6

Unusual specific heat behavior near x ~ 0.6

Additional anomaly observed at x ~ 0.9

Abstract

The solid-solution SrRu$_{1-x}$Rh$_x$O$_3$ ($0\le x \le1$) is a variable-electron-configuration system forming in the nearly-cubic-perovskite basis, ranging from the ferromagnetic 4$d^4$ to the enhanced paramagnetic 4$d^5$. Polycrystalline single-phase samples were obtained over the whole composition range by a high-pressure-heating technique, followed by measurements of magnetic susceptibility, magnetization, specific heat, thermopower, and electrical resistivity. The ferromagnetic order in long range is gradually suppressed by the Rh substitution and vanishes at $x \sim 0.6$. The electronic term of specific-heat shows unusual behavior near the critical Rh concentration; the feature does not match even qualitatively with what was reported for the related perovskites (Sr,Ca)RuO$_3$. Furthermore, another anomaly in the specific heat was observed at $x \sim 0.9$.