Evolution of ferrimagnetism against Griffiths singularity in Calcium Ruthenate

TL;DR

This study investigates how Cr doping influences the magnetic and electronic properties of CaRuO₃, revealing a transition from paramagnetic to ferrimagnetic states and the emergence of Griffiths singularity, with implications for understanding correlated metal magnetism.

Contribution

It uncovers the evolution of ferrimagnetism and Griffiths singularity in CaRuO₃ due to Cr doping, introducing a new phase diagram and explaining magnetic clustering mechanisms.

Findings

Tiny Cr doping induces ferrimagnetism in CaRuO₃.

Higher Cr doping leads to Griffiths singularity and magnetic clustering.

Cr doping causes a transition to non-metallic conduction, following Mott-VRH behavior.

Abstract

The magnetism in the correlated metal CaRuO$_3$ is enigmatic as it is poised near a triple point among the ferromagnetic, antiferromagnetic, and paramagnetic ground states. Here we report a detailed work on structural, spectroscopic, magnetic, and transport properties in CaRu$_{1-x}$Cr$_x$O$_3$. We find that Cr doping reduces the orthorhombicity in CaRuO$_3$. Surprisingly, a tiny (x = 0.01) amount of Cr-doping drives the magnetic ground state from \enquote{paramagnetic-like} to ferrimagnetic. Slightly higher Cr-doping (x = 0.05) results formation of magnetic clusters which gives rise to Griffiths singularity and power law divergence in magnetic susceptibility. The magnetism in CaRu$_{1-x}$Cr$_x$O$_3$ is explained in terms of \enquote{seven atom} ferrimagnetic clusters. Electrical transport shows a gradual evolution of a non-metallic state upon Cr-doping. In particular, for x $\geq$ 0.1, the temperature-dependent resistivity follows Mott-VRH conduction. The XPS study also supports significant role of disorder and electron correlation which effectively reduces the itinerant character of electrons. Finally, a new T-x phase diagram is constructed depicting the evolution of electronic and magnetic state in CaRu$_{1-x}$Cr$_x$O$_3$.