Cooperative dynamics in doped manganite films: phonon anomalies in the ferromagnetic state

Abstract

We present optical measurements of phononic excitations in La${}_{2/3}$Ca${}_{1/3}$MnO${}_3$ (LCMO) and La${}_{2/3}$Sr${}_{1/3}$MnO${}_3$ (LSMO) thin films covering the full temperature range from the metallic ferromagnetic to the insulating paramagnetic phase. All eight phonons expected for the R$\bar{3}$c symmetry in LSMO and 17 out of the expected 25 phonons for the Pnma symmetry in LCMO have been determined. Close to the ferromagnetic-to-paramagnetic transition both compounds reveal an anomalous behavior but with different characteristics. Anomalies in the phononic spectra are a manifestation of the coupling of lattice degrees of freedom (DOF) to electronic DOF. Specifically, the low-frequency external group proves to be an indicator for lattice modifications induced by electronic correlations. The enhanced electron-phonon coupling in LCMO is responsible for Fano-like interference effects of distinct phonon modes with electronic continuum excitations: we observe asymmetric phonon line shapes, mode splitting and spectral weight transfer between modes.

arXiv comment10 pages, 10 figures

References in corpus (10)

• Double Exchange Alone Does Not Explain the Resistivity of $L{a}_{1-x}S{r}_{x}Mn{O}_3$
• Magnetism and Structural Distortion in the La0.7Sr0.3MnO3 Metallic Ferromagnet
• Orbital Liquid in Perovskite Transition-Metal Oxides
• Infrared spectroscopic study of phonons coupled to charge excitations in FeSi
• Optical conductivity of colossal magnetorestistance compounds: Role of orbital degeneracy in the ferromagnetic phase
• Evidence of magnetization-dependent polaron formation in La${}_{1-x}{A}_x$MnO${}_3$, $A$=Ca, Pb
• Infrared Studies of a La_{0.67}Ca_{0.33}MnO_3 Single Crystal: Optical Magnetoconductivity in a Half-Metallic Ferromagnet
• Physical origin of the buckling in CuO${}_2$: Electron-phonon coupling and Raman spectra
• Large and Small Polaron Excitations in La2/3(Sr/Ca)1/3MnO3 Films
• Fano effect in the $a-b$ plane of Nd${}_{1.96}$Ce${}_{0.04}$CuO${}_{4+y}$: evidence of phonon interaction with a polaronic background

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• Isotropic Kink and Quasiparticle Excitations in the Three-Dimensional Perovskite Manganite La${}_{0.6}$Sr${}_{0.4}$MnO${}_3$
• Phonon-Metamorphosis in Ferromagnetic Manganite Films: Probing the Evolution of an Inhomogeneous State
• Optical Evidence for Mixed Phase Behavior in Manganites
• Dynamic conductivity of semiconducting manganites approaching the metal-insulator transition