Properties of the n=3 Ruddlesden-Popper Phases Sr4Mn3-xFexO10-delta (x= 1, 1.5, 2)

We have prepared a series of Fe-substituted Sr4Mn3-x FexO10-delta strontium manganates with x=1, 3/2, and 2. These compounds adopt the n=3 Ruddlesden-Popper structure (I4/mmm), unlike the parent compound Sr4Mn3O10, which contains a network of face-sharing MnO6 octahedra, with the larger Fe ion preferentially occupying the Mn/Fe (1) middle layer of the corner-sharing trioctahedra slabs. We have investigated their physical properties with X-ray diffraction, X-ray absorption near edge spectroscopy, M?ssbauer spectroscopy, variable temperature resistivity, and magnetic susceptibility. In addition, for the x=2 compound we preformed room temperature neutron diffraction experiments. These compounds need to be formed at high temperatures; as a consequence they are oxygen deficient and contain some Fe3+. They are insulators and exhibit spin-glass-like transitions at low temperature.