Jahn-Teller transition inLa1−xSrxMnO3in the low-doping region(0<x<~0.1)

Abstract

We have investigated the Jahn-Teller transition in ${\mathrm{La}}_{1\ensuremath{-}x}{\mathrm{Sr}}_{x}{\mathrm{MnO}}_{3}$ by high-temperature powder neutron diffraction in the low-doping region $(0lxl~0.1).$ The Jahn-Teller transition temperature which is about ${T}_{\mathrm{JT}}\ensuremath{\approx}750\mathrm{K}$ for stoichiometric ${\mathrm{LaMnO}}_{3}$ is drastically reduced on doping with Sr, becoming ${T}_{\mathrm{JT}}\ensuremath{\approx}475\mathrm{K}$ for $x=0.10.$ The previously identified metrically cubic orthorhombic O phase (Pmnb) for $x=0$ becomes clearly (also metrically) orthorhombic for small doping $x=0.05$ and remains so in the doping range investigated. The Jahn-Teller transition is accompanied only by the partial reduction of the distortion of the ${\mathrm{MnO}}_{6}$ octahedra. From the distortion of the ${\mathrm{MnO}}_{6}$ octahedra we have determined the orbital mixing coefficients.