Magnetic Properties of the Fluorite-Related La3MO7 Phases, M=Ru and Os: Local Moment Magnetism, Short- and Long-Range Order in 4d and 5d Transition Metal Oxides
✍ Scribed by Robert Lam; Frederick Wiss; John E. Greedan
- Publisher
- Elsevier Science
- Year
- 2002
- Tongue
- English
- Weight
- 195 KB
- Volume
- 167
- Category
- Article
- ISSN
- 0022-4596
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✦ Synopsis
The oxide materials La 3 MO 7 , M=Ru and Os have been prepared, the Os phase for the first time. Both crystallize in a fluorite-related supercell with Cmcm symmetry with very similar lattice constants. A singular feature of this structure type is the presence of well-separated zig-zag chains of corner-sharing MO 6 octahedra parallel to one of the orthorhombic axes. Local moment magnetic behavior is observed for both on very different energy scales. In each case the materials exhibit Curie-Weiss paramagnetism at high temperatures with effective moments consistent with S ¼ 3 2 ; as expected for the 4d 3 and 5d 3 electronic configurations associated with oxidation state +5, thus providing evidence for local moment magnetism. At lower temperatures broad maxima occur near 20 K (Ru) and 110 K(Os) which can be attributed to intrachain magnetic correlations. Fits to an appropriate model yield J intra =k values of À2.9 K for Ru and À23.2(1) K for Os. This Beight-fold increase is attributed to the expanded radial extent of the d-orbitals in proceeding from the 4d to the 5d series. Evidence for long-range antiferromagnetic order is present in the form of sharp susceptibility maxima at 10 and 45 K for M=Ru and Os, respectively. # 2002 Elsevier Science (USA)