W0022

Incommensurate Jahn-Teller Polaron Correlations in Bilayered Colossal Magnetoresistive Manganite La_1.2Sr_1.8Mn₂O_7. Branton J. Campbell^1,2*, Ray Osborn², Dimitri N. Argyriou^3,2*, John F. Mitchell², Lida Vasiliu-Doloc⁴, Uta Ruett⁴, Zahir Islam⁴, Chris D. Ling², Sunil K. Sinha^5,4*; ¹Dept. of Physics & Astronomy, Brigham Young U.; ²Materials Science Div., Argonne National Laboratory; ³Hahn-Meitner Institute, Berlin Germany; ⁴Advanced Photon Source, Argonne National Laboratory; ⁵Dept. of Physics, U.C. San Diego. * Indicates a previous affiliation.

Evidence of short-range polaron correlations have been observed in the layered perovskite manganite La_1.2Sr_1.8Mn₂O_7, where weak diffuse satellites were observed at positions separated from strong Bragg reflections by q _ (0.3,0,_1). Here, the intensities of 109 of these diffuse satellites have been determined from high-energy x-ray scattering measurements and used to perform a crystallographic analysis of the associated atomic displacements. The resulting structure is a one-dimensional modulation of the parent I/4mmm structure along (100) that is primarily longitudinal in character, but which also possesses a transverse (001) component. These displacements reveal a nanoscale ordering (_~25Å) of the e_g electrons into d(3x²-r²) orbitals that forms a “striped” arrangement of Jahn-Teller distorted octahedra. The two 90-degree twin orientations were observed in equal proportions. A least-squares refinement of this model using the JANA software package yields a weighted residual factor of 13.5% (12 parameters and 109 observations). This work was supported by U.S. DOE Office of Science (W-31-109-ENG-38).