Measurement of the local Jahn-Teller distortion in LaMnO 3.006

The atomic pair distribution function (PDF) of stoichiometric LaMnO{sub 3} has been measured. This has been fit with a structural model to extract the {ital local} Jahn-Teller distortion for an ideal Mn{sup 3+}O{sub 6} octahedron. These results are compared to Rietveld refinements of the same data which give the {ital average} structure. Since the {ital local} structure is being measured in the PDF there is no assumption of long-range orbital order and the real, local, Jahn-Teller distortion is measured directly. We find good agreement both with published crystallographic 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 two long bonds. This implies that there is some mixing of the d{sub 3z{sup 2}{minus}r{sup 2}} and d{sub x{sup 2}{minus}y{sup 2}} states and the occupied state is not pure d{sub 3z{sup 2}{minus}r{sup 2}} symmetry. The Debye temperature of the Mn and O ions has also been calculated as {Theta}{sub D}(Mn)=1000{plus_minus}100hK, {Theta}{sub D}(O{sub apical})=980{plus_minus}30hK, and {Theta}{sub D}(O{sub basal})=601{plus_minus}8hK. {copyright} {ital 1999} {ital The American Physical Society}