Strain induced stabilization of a static Jahn-Teller distortion in the O\(^\)-phase of La\(_{7/8}\)Sr\(_{1/8}\)MnO\(_3\)

At room temperature, bulk La\(_{7/8}\)Sr\(_{1/8}\)MnO\(_3\) is in the dynamic Jahn--Teller O\(^*\) phase, but undergoes a transition to a static, magnetically ordered Jahn--Teller phase at lower temperatures. Here we study a \(6\) unit cells thin film of this compound grown on SrTiO\(_3\), resulting...

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Published inarXiv.org
Main Authors Dettbarn, Michael, Zabolotnyy, Volodymyr B, Tcakaev, Abdul V, Sutarto, Ronny, He, Feizhou, Chen, Yunzhong, Green, Robert J, Hinkov, Vladimir
Format Paper
LanguageEnglish
Published Ithaca Cornell University Library, arXiv.org 13.11.2020
Subjects
Compressive properties
Configurations
Field theory
Jahn-Teller effect
Ligands
Magnetic moments
Magnetic properties
Manganese oxides
Phase transitions
Room temperature
Spin transition
Strontium
Thin films
Wave functions
X ray absorption
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Summary:At room temperature, bulk La\(_{7/8}\)Sr\(_{1/8}\)MnO\(_3\) is in the dynamic Jahn--Teller O\(^*\) phase, but undergoes a transition to a static, magnetically ordered Jahn--Teller phase at lower temperatures. Here we study a \(6\) unit cells thin film of this compound grown on SrTiO\(_3\), resulting in small compressive strain due to a lattice mismatch of \(\lesssim 0.2\%\). We combine X-ray absorption spectroscopy with multiplet ligand field theory to study the local electronic and magnetic properties of Mn in the film. We determine the Mn \(d_{3z^2-r^2}\) orbital to be \(0.13\;\text{eV}\) lower in energy than the \(d_{x^2-y^2}\), which is a disproportionately large splitting given the small degree of compressive strain. We interpret this as resulting from the strain providing a preferential orientation for the MnO\(_6\) octahedra, which are strongly susceptible to such a deformation in the vicinity of the phase transition. Hence, they collectively elongate along the \(c\) axis into a static Jahn--Teller arrangement. Furthermore, we demonstrate the strongly covalent character of La\(_{7/8}\)Sr\(_{1/8}\)MnO\(_3\), with a contribution of nearly \(50\%\) of the one-ligand-hole configuration \(d^{5} \underline{L}^1\) to the ground state wavefunction. Finally, we find the system to be in a high-spin configuration, with the projection of the local magnetic moment on the quantization axis being about \(3.7\;\mu_{\text{B}}/\text{Mn}\). We show, however, that the system is close to a high-spin--low-spin transition, which might be triggered by crystal field effects.
ISSN:2331-8422