Monday, 23 May 2005

This presentation is part of: Solid State and Materials Chemistry Posters

SrFe1/4Re3/4O3: A metallic ferromagnetic double perovskite with an uncommon octahedral tilt as revealed by high-resolution synchrotron powder X-ray diffraction

Louis W. Whaley1, Martha Greenblatt1, Mark C. Croft2, and Kandalam V. Ramanujachary3. (1) Rutgers, The State University of New Jersey, Piscataway, NJ, (2) Rutgers University, Piscataway, NJ, (3) Rowan University, Glassboro, NJ

Structural, magnetic and transport characterization of a metallic, ferromagnetic double perovskite with 3d5d orbital interactions, nominally SrFe1/4Re3/4O3, has been performed. Synchrotron x-ray powder diffraction (SPXD) reveals an orthorhombic structure with an uncommon a+b+c+ Glazer octahedral tilt system (Pnnn, a = 7.87422(4); b = 7.87726(6); c = 7.89795(4); χ2 = 3.125%; Rwp = 8.06%; Rp = 6.47%; 35 variables), with a slight symmetry lowering distortion (P2nn,a = 7.87722(6) ; b = 7.87433(4); c = 7.89800(4); χ2 = 2.90; Rwp = 7.42; Rp = 6.10; 45 variables). Fe-K-edge and Re L3-edge XANES data support Fe(III) and mixed valent Re(IV/VI). Temperature-dependent magnetic susceptibility reveals ordering near 150 K and a hysteretic field-dependent magnetization indicates "ferromagnetism" (or ferrimagnetism but with a small, nearly vanishing contribution from the rhenium moment). Ordering of the B-site and the nearly linear B(Fe/Re)-O-B'(Re) bond angles (~170 ) apparently enhance magnetic exchange and (metallic) charge transport near room temperature (ρRT ≈ 2.5 mΩ-cm). A shallow resistivity minimum at 40 K (ρ40K ≈ 1.9 mΩ-cm) resembling a metal-semiconductor transition is attributed to weak localization.

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