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Title: A family of rare earth molybdenum bronzes: Oxides consisting of periodic arrays of interacting magnetic units

The family of rare earth molybdenum bronzes, reduced ternary molybdates of composition LnMo{sub 16}O{sub 44,} was synthesized and a detailed structural study carried out. Bond valence sum (BVS) calculations clearly show that the molybdenum ions in tetrahedral coordination are hexavalent while the electron count in the primitive unit cell is odd. Yet, measurements show that the phases are semiconductors. The temperature dependence of the magnetic susceptibility of samples containing several different rare earth elements was measured. These measurements verified the presence of a 6.5 K magnetic phase transition not arising from the rare earth constituent, but likely associated with the unique isolated ReO{sub 3}-type Mo{sub 8}O{sub 36} structural subunits in this phase. To better understand the behavior of these materials, electronic structure calculations were performed within density functional theory. Results suggest a magnetic state in which these structural moieties have an internal ferromagnetic arrangement, with small ~1/8 μ{sub B} moments on each Mo. We suggest that the Mo{sub 8}O{sub 36} units behave like pseudoatoms with spin 1/2 derived from a single hole distributed over the eight Mo atoms that are strongly hybridized with the O atoms of the subunit. Interestingly, while the compound is antiferromagnetic, our calculations suggest that amore » field-stabilized ferromagnetic state, if achievable, will be a narrow band half-metal. - Graphical abstract: LnMo{sub 16}O{sub 44} phases comprise corner sharing tetrahedral and octahedral molybdenum ions. The MoO{sub 6} octahedra form Mo{sub 8}O{sub 36} units that are well separated and act like pseudo-atoms, accommodating 11 electrons each. - Highlights: • Single crystal X-ray diffraction refinements of LnMo{sub 16}O{sub 44} single crystals for Ln=Ce, Pr, Nd, Tb, Dy and Ho. • DFT calculations based on LaMo{sub 16}O{sub 44}. • [Mo{sub 8}O{sub 36}] units behaving as superatoms with a net magnetic moment of 1 µ{sub B}. • Bronze structure containing equal number of molybdenum tetrahedra and octahedral.« less
Authors:
 [1] ;  [2] ;  [3] ;  [4] ;  [2] ;  [3] ;  [2] ;  [3] ;  [5]
  1. Department of Chemistry, Montclair State University, Montclair, NJ 07043 (United States)
  2. Department of Chemical and Biomedical Engineering, FAMU-FSU College of Engineering, Tallahassee, FL 32310 (United States)
  3. (United States)
  4. National High Magnetic Field Laboratory, Tallahassee, FL 32310 (United States)
  5. Materials Science and Technology Division, Oak Ridge National Laboratory, Oak Ridge, TN 37831-6056 (United States)
Publication Date:
OSTI Identifier:
22475696
Resource Type:
Journal Article
Resource Relation:
Journal Name: Journal of Solid State Chemistry; Journal Volume: 227; Other Information: Copyright (c) 2015 Elsevier Science B.V., Amsterdam, The Netherlands, All rights reserved.; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
37 INORGANIC, ORGANIC, PHYSICAL AND ANALYTICAL CHEMISTRY; ANTIFERROMAGNETISM; ATOMS; BRONZE; CRYSTAL STRUCTURE; DENSITY FUNCTIONAL METHOD; ELECTRONIC STRUCTURE; HOLES; LANTHANUM COMPOUNDS; MAGNETIC MOMENTS; MAGNETIC SUSCEPTIBILITY; MOLYBDATES; MOLYBDENUM IONS; MONOCRYSTALS; PHASE TRANSFORMATIONS; RHENIUM OXIDES; SEMICONDUCTOR MATERIALS; TEMPERATURE DEPENDENCE; VALENCE; X-RAY DIFFRACTION