Local lattice distortions inLa1−xSrxMnO3studied by pulsed neutron scattering

Abstract

Pulsed neutron-diffraction measurements were carried out on powder samples of ${\mathrm{La}}_{1\ensuremath{-}x}{\mathrm{Sr}}_{x}{\mathrm{MnO}}_{3}$ $(0l~xl~0.5)$ in order to study the local atomic structure of this system known for its colossal magnetoresistance phenomenon. The results are analyzed in terms of the atomic pair-density function to elucidate the role of local lattice distortion in the magnetic and charge transport properties. It is shown that the Jahn-Teller (JT) distortions are locally present even when the crystallographic structure suggests otherwise, and indicate the formation of small lattice polarons in the insulating phase. Local JT distortions are observed even in the metallic phase up to $x=0.35,$ suggesting that the charge distribution in the metallic phase just above the metal-insulator transition may not be spatially uniform. It is possible that charges are partially confined by spin and lattice resulting in microscopic separation of the charge-rich and charge-poor regions.