Structurally modulated magnetic properties in the A3MnRu2O9 phases (A = Ba, Ca): the role of metal-metal bonding in perovskite-related oxides

Serpil Gonen, Z. ; Gopalakrishnan, J. ; Eichhorn, B. W. ; Greene, Richard L. (2001) Structurally modulated magnetic properties in the A3MnRu2O9 phases (A = Ba, Ca): the role of metal-metal bonding in perovskite-related oxides Inorganic Chemistry, 40 (19). pp. 4996-5000. ISSN 0020-1669

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Official URL: http://pubs.acs.org/doi/abs/10.1021/ic0013431

Related URL: http://dx.doi.org/10.1021/ic0013431

Abstract

Ca3MnRu2O9 and Ba3MnRu2O9 were synthesized from transition metal dioxides and alkaline earth metal carbonates at 1100-1300°C. Ca3MnRu2O9 adopts the prototypical GdFeO3-type perovskite structure with Mn and Ru statistically disordered over the single metal atom site. The susceptibility shows Curie-Weiss behavior above 240 K with μeff = 3.14 μB/metal atom, which is in excellent agreement with the expected spin-only moment of 3.20 μB. Below 150 K, the compound shows spin-glass-like short-range ferrimagnetic correlations. The high-temperature region of the electrical resistivity reveals a small activation energy of 17(1) meV whereas the low-temperature region is nonlinear and does not fit a variable range hopping model. Ba3MnRu2O9 crystallizes in the 9-layer BaRuO3-type structure containing M3O12 face-shared trioctahedral clusters in which Mn and Ru are statistically disordered. Ba3MnRu2O9 shows nonlinear reciprocal susceptibility at all temperatures and is described by a variable-spin cluster model with an S = ½ ground state with thermally populated excited states. The low spin value of this system (S = ½) is attributed to direct metal-metal bonding. Below 30 K, the compound shows short-range magnetic correlations and spin-glass-like behavior. The high-temperature region of the electrical resistivity indicates a small activation energy of 8.8(1) meV whereas the low-temperature region is nonlinear. The importance of metal-metal bonding and the relationships to other related compounds are discussed.

Item Type:Article
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ID Code:12978
Deposited On:11 Nov 2010 08:17
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