Griffiths singularity and magnetic phase diagram of La1-xCaxCoO3

TL;DR

This study investigates the magnetic properties of La$_{1-x}$Ca$_{x}$CoO$_{3}$, revealing a Griffiths phase above the ferromagnetic transition temperature and establishing a detailed magnetic phase diagram for Ca-doped cobaltites.

Contribution

It provides the first detailed analysis of Griffiths singularity in La$_{1-x}$Ca$_{x}$CoO$_{3}$ and compares it with other doped cobaltites, highlighting the role of dopant size in magnetic interactions.

Findings

Presence of Griffiths phase above $T_C$ in Ca-doped cobaltites

Distinct magnetic clustering behavior compared to Sr- and Ba-doped cobaltites

Proposed correlation between dopant size and magnetic interaction nature

Abstract

Magnetic properties of La$_{1-x}$Ca$_{x}$CoO$_{3}$ (0.10 $\leq x\leq$ 0.25) are systemically studied in this work. All the samples exhibits the ferromagnetic state at low temperatures. However, their inverse low-field magnetic susceptibilities shows a sharply downward deviation from high-temperature Curie-Weiss paramagnetic behavior well above the ferromagnetic transition temperature ($T_C$), which indicates the presence of a ferromagnetic clustered state above $T_C$. A detailed analysis on the susceptibilities reveals that the short-range state in these Ca-doped samples can be well described as the Griffiths phase. This characteristic is quite different from those of the clustered states above $T_C$ recently reported in Sr- and Ba-doped cobaltites, which are non-Griffith-like. It is proposed that this difference possibly arises from the unique dependence of magnetic interactions among Co$^{3+}$ ions on the size of the dopant in the doped cobaltites. Based on these results, the magnetic diagram of the Ca-doped cobaltites is established.