Measurement of the local Jahn-Teller distortion in LaMnO3.006

The atomic pair distribution function (PDF) of stoichiometric LaMnO3 has be en measured. This has been fit with a structural model to extract the local Jahn-Teller distortion for an ideal Mn3+O6 octahedron. These results are c ompared to Rietveld refinements of the same data which give the average str ucture. Since the local structure is being measured in the PDF there is no assumption of long-range orbital order and the real, local, Jahn-Teller dis tortion is measured directly. We find good agreement both with published cr ystallographic results and our own Rietveld refinements suggesting that in an accurately stoichiometric material there is long-range orbital order as expected. The local Jahn-Teller distortion has two short, two medium, and t wo long bonds. This implies that there is some mixing of the d(3z)(-r)(2)(2 ), and d(x)(-y)(2)(2) states and the occupied state is not pure d(3z)(-r)(2 )(2) symmetry. The Debye temperature of the Mn and O ions has also been cal culated as OD(Mn) = 1000 +/- 100 K, Theta(D)( O-apical) = 980 +/- 30 K, and Theta(D)(O-basal) = 601 +/- 8 K [S0163 -1829(99)05238-8].