Cluster-glass state in manganites induced byA-site cation-size disorder

• DOI: 10.1103/physrevb.73.134411
• Publication Date: 2006-04-11T22:50:19Z
• Authors: K. F. Wang; Y. Wang; L. F. Wang; S. Dong; D. Li; Z. D. Zhang; H. Yu; Q. C. Li; J.-M. Liu
• Keywords: Ionic radius; Lattice (music)

The dependence of magnetotransport behaviors on $A$-site disorder induced by cational size mismatch in ferromagnetic manganites is investigated characterizing a series samples with the same mean radius $⟨{r}_{A}⟩=1.20\phantom{\rule{0.3em}{0ex}}\mathrm{\AA{}}$ but different ionic radii variance ${\ensuremath{\sigma}}^{2}={\ensuremath{\sum}}_{i}{x}_{i}{r}_{i}^{2}\ensuremath{-}{⟨{r}_{A}⟩}^{2}$, where ${x}_{i}$ and ${r}_{i}$ are atomic fraction $i$-type ions at $A$-site, respectively. It revealed that ground state transits from metal to cluster-glass insulator upon increasing ${\ensuremath{\sigma}}^{2}$ 0.0003 for ${\mathrm{La}}_{0.55}{\mathrm{Ca}}_{0.45}\mathrm{Mn}{\mathrm{O}}_{3}$ 0.015 ${\mathrm{Sm}}_{0.55}{({\mathrm{Ca}}_{0.6}{\mathrm{Ba}}_{0.4})}_{0.45}\mathrm{Mn}{\mathrm{O}}_{3}$, while crystallographic structure lattice constants these remain unchanged. Nevertheless, believed enhance random local radial distortion $\mathrm{Mn}{\mathrm{O}}_{6}$ octahedra suppress long-range order. In high disorder, ordering completely melted into short-range magnetically ordered clusters then stepwise magnetization. With decreasing temperature, become frustrated frustrating point, below which transition occurs due weak intercluster interaction.