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

Lynn Schneemeyer, T. Siegrist, T. Besara, M. Lundberg, J. Sun, D. J. Singh

Research output: Contribution to journalArticle

2 Citations (Scopus)

Abstract

The family of rare earth molybdenum bronzes, reduced ternary molybdates of composition LnMo16O44, 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 ReO3-type Mo8O36 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 μB moments on each Mo. We suggest that the Mo8O36 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 a field-stabilized ferromagnetic state, if achievable, will be a narrow band half-metal.

Original languageEnglish
Pages (from-to)178-185
Number of pages8
JournalJournal of Solid State Chemistry
Volume227
DOIs
StatePublished - 1 Jul 2015

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Molybdenum
Bronze
bronzes
Oxides
Rare earths
molybdenum
rare earth elements
oxides
Atoms
molybdates
Rare earth elements
Magnetic susceptibility
Electronic structure
Density functional theory
atoms
narrowband
Phase transitions
Metals
Ions
Semiconductor materials

Keywords

  • Crystallographic structure
  • DFT calculations
  • Magnetism
  • Mo<inf>8</inf>O<inf>36</inf> units
  • Molybdenum bronzes

Cite this

Schneemeyer, Lynn ; Siegrist, T. ; Besara, T. ; Lundberg, M. ; Sun, J. ; Singh, D. J. / A family of rare earth molybdenum bronzes : Oxides consisting of periodic arrays of interacting magnetic units. In: Journal of Solid State Chemistry. 2015 ; Vol. 227. pp. 178-185.
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A family of rare earth molybdenum bronzes : Oxides consisting of periodic arrays of interacting magnetic units. / Schneemeyer, Lynn; Siegrist, T.; Besara, T.; Lundberg, M.; Sun, J.; Singh, D. J.

In: Journal of Solid State Chemistry, Vol. 227, 01.07.2015, p. 178-185.

Research output: Contribution to journalArticle

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AB - The family of rare earth molybdenum bronzes, reduced ternary molybdates of composition LnMo16O44, 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 ReO3-type Mo8O36 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 μB moments on each Mo. We suggest that the Mo8O36 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 a field-stabilized ferromagnetic state, if achievable, will be a narrow band half-metal.

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