Sr3Mn2O7:Mn4+ parent compound of the n=2 layered CMR manganites

We report the crystal and magnetic structures of the bilayer Ruddlesden-Popper phase Sr3Mn2O7-delta (delta=0.0, 0.45), The delta = 0.45 compound exhibits a large number of oxygen vacancies disordered in the MnO2 planes and is a nonmagnetic insulator. Sr3Mn2O7.0 (delta = 0) in an antiferromagnetic insulator whose magnetic structure is analogous to that of the related SrMnO3 perovskite, The stoichiometric layered material has a small distortion of its exclusively Mn4+O6 octahedra as a result of steric influence of the surrounding cations, Thus, it provides a baseline for structural distortions related to electronic and/or magnetic transitions in doped materials. (C) 1998 Academic Press.