Incommensurate sinusoidal oxygen modulations in layered manganites La(1-x)Sr(1+x)MnO4 (x≥0.5).

ABSTRACT

We have studied the incommensurate-ordered phase in overdoped La0.4Sr1.6MnO4 by resonant x-ray diffraction at the Mn K edge. Weak resonant superlattice (h±0.2 h±0.2 0) and (h±0.4 h±0.4 0) reflections of the tetragonal structure were found below ~240 K. The energy, azimuth angle, and polarization dependencies of the resonant scattering have revealed sinusoidal modulations of the oxygen motions that are transverse and longitudinal to the tetragonal [110] direction. This result discards (Mn(3+),Mn(4+))-like stripe-type order but point to a charge-density-modulation picture.