Structural aspects of the phonon spectra ofLa1−xSrxMnO3

Abstract

The lightly doped ${\mathrm{La}}_{1-x}{\mathrm{Sr}}_x{\mathrm{MnO}}_3$ system was investigated using x-ray diffraction and far-infrared spectroscopy in the insulating range for $x⩽0.125$ on single crystalline samples. Special emphasis was set on the evolution of the Jahn-Teller (JT) distortion. With increasing doping concentration $x$ the optical phonon excitations broaden and merge into three groups, consistent with a weakening of the orthorhombic JT distortion. The temperature and doping dependence of the phonon anomalies are related to the complex phase diagram, which is governed by electronic, magnetic, and structural degrees of freedom. Indications for a magnon-phonon coupling are found for specific phonon modes.