  In this paper we present the results of a high temperature (300 K<T<800 K)
neutron powder diffraction study of the La1.4Sr1.6Mn2O7 bilayered manganite. An
unusual trend of the <Mn-Oapical>/Mn-Oequatorial parameter was found: it first
decreases up to 500 K and then increases up to the highest T measured. At the
same time, a significant shortening of the apical Mn-O(2) bond is observed in
the range where the J-T distortion is reduced. The overall data gained by this
study may suggest a shift of electronic density from axial to planar eg
orbitals with T. This trend is explained considering of the presence of short
range magnetic interaction well above TC.
