Magnetic properties of La1−xCaxCoO3 (0.10 ≤x≤ 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 (TC), which indicates the presence of a ferromagnetic clustered state above TC. 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 TC 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 Co3+ 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.
@article{arxiv.1207.2818,
title = {Griffiths singularity and magnetic phase diagram of La1-xCaxCoO3},
author = {Shiming Zhou and Yuqiao Guo and Laifa He and Jiyin Zhao and Lei Shi},
journal= {arXiv preprint arXiv:1207.2818},
year = {2012}
}