Quadrupolar effect in the perovskite manganiteLa1−xSrxMnO3
| Autor: | Hirofumi Hazama, Terutaka Goto, Yoshinori Tokura, Yasuhide Tomioka, Yuichi Nemoto, Atsushi Asamitsu |
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| Rok vydání: | 2000 |
| Předmět: | |
| Zdroj: | Physical Review B. 62:15012-15020 |
| ISSN: | 1095-3795 0163-1829 |
| Popis: | Elastic properties of the perovskite manganite ${\mathrm{La}}_{1\ensuremath{-}x}{\mathrm{Sr}}_{x}{\mathrm{MnO}}_{3}(x=0.12,0.165,0.3)$ with both orbital and charge degrees of freedom have been investigated by means of ultrasonic measurements. Above the structural phase transition point ${T}_{s}=290\mathrm{K}$ for $x=0.12$ and ${T}_{s}=310\mathrm{K}$ for $x=0.165,$ the transverse ${(C}_{11}\ensuremath{-}{C}_{12})/2$ mode with the elastic strain of ${E}_{g}$ symmetry exhibits a pronounced softening, while the ${C}_{44}$ mode with strain of ${T}_{2g}$ symmetry shows a monotonous increase in lowering temperature. The softening of ${(C}_{11}\ensuremath{-}{C}_{12})/2$ is described in terms of the quadrupolar susceptibility for the coupling between the quadrupolar moment, ${O}_{2}^{0}{=(2l}_{z}^{2}\ensuremath{-}{l}_{x}^{2}\ensuremath{-}{l}_{y}^{2})/\sqrt{3}$ and ${O}_{2}^{2}{=l}_{x}^{2}\ensuremath{-}{l}_{y}^{2},$ of the $d\ensuremath{\gamma}$ doublet of the ${\mathrm{Mn}}^{3+}$ ion and the appropriate elastic strain with ${E}_{g}$ symmetry. Elastic softenings of ${(C}_{11}\ensuremath{-}{C}_{12})/2$ and ${C}_{44}$ modes above ${T}_{\mathrm{co}}=145\mathrm{K}$ of $x=0.12$ are responsible for the symmetry breaking character of the charge ordering, while a round minimum of the bulk modulus ${C}_{B}$ around ${T}_{\mathrm{co}}=100\mathrm{K}$ of $x=0.165$ indicates a glass state in charge ordering. The disappearance of the ultrasonic echo signal below ${T}_{\mathrm{co}}=145\mathrm{K}$ for $x=0.12$ is ascribed to a considerable sound wave scattering by elastic domains in the triclinic structure. |
| Databáze: | OpenAIRE |
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