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Title: Structural and metal-insulator transitions in rhenium-based double perovskites via orbital ordering

Authors:
;
Publication Date:
Sponsoring Org.:
USDOE
OSTI Identifier:
1415530
Grant/Contract Number:
SC0016507; AC02-05CH11231
Resource Type:
Journal Article: Publisher's Accepted Manuscript
Journal Name:
Physical Review B
Additional Journal Information:
Journal Volume: 97; Journal Issue: 4; Related Information: CHORUS Timestamp: 2018-01-03 18:01:23; Journal ID: ISSN 2469-9950
Publisher:
American Physical Society
Country of Publication:
United States
Language:
English

Citation Formats

Lee, Alex Taekyung, and Marianetti, Chris A. Structural and metal-insulator transitions in rhenium-based double perovskites via orbital ordering. United States: N. p., 2018. Web. doi:10.1103/PhysRevB.97.045102.
Lee, Alex Taekyung, & Marianetti, Chris A. Structural and metal-insulator transitions in rhenium-based double perovskites via orbital ordering. United States. doi:10.1103/PhysRevB.97.045102.
Lee, Alex Taekyung, and Marianetti, Chris A. Wed . "Structural and metal-insulator transitions in rhenium-based double perovskites via orbital ordering". United States. doi:10.1103/PhysRevB.97.045102.
@article{osti_1415530,
title = {Structural and metal-insulator transitions in rhenium-based double perovskites via orbital ordering},
author = {Lee, Alex Taekyung and Marianetti, Chris A.},
abstractNote = {},
doi = {10.1103/PhysRevB.97.045102},
journal = {Physical Review B},
number = 4,
volume = 97,
place = {United States},
year = {Wed Jan 03 00:00:00 EST 2018},
month = {Wed Jan 03 00:00:00 EST 2018}
}

Journal Article:
Free Publicly Available Full Text
This content will become publicly available on January 3, 2019
Publisher's Accepted Manuscript

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  • RNiO{sub 3} nickelates have been prepared under high oxygen pressure (R = Sm, Eu, Gd) or high hydrostatic pressure (R = Dy, Ho, Y) in the presence of KClO{sub 4}. The samples have been investigated at room temperature (RT) by synchrotron X-ray powder diffraction to follow the evolution of the crystal structures and microstructures along the series. The distortion of the orthorhombic (space group Pbnm) perovskite progressively increases along the series, leading for the smallest Ho{sup 3+} and Y{sup 3+} cations to a subtle monoclinic distortion (space group P2{sub 1}/n) which implies the splitting of the Ni positions in themore » crystal. This symmetry was confirmed by neutron powder diffraction; the crystal structures for R = Ho and Y were refined simultaneously from RT synchrotron and neutron powder diffraction data. In both perovskites the oxygen octahedra around Ni1 and Ni2 positions are significantly distorted, suggesting the manifestation of Jahn-Teller effect, which is almost absent in the nickelates` of lighter rare earths. The very distinct mean Ni-O bond distances observed for Ni1 and Ni2 atoms at RT, in the insulating regime, suggest the presence of a charge disproportionation effect, considered as driving force for the splitting of the Ni positions. The metal-insulator (MI) transitions for RNiO{sub 3} (R = Gd, Dy, Ho, Y), above room temperature, have been characterized by DSC. The transition temperatures for Gd, Dy, Ho, and Y oxides in the heating runs are 510.7, 563.9, 572.7, and 581.9 K, respectively. The increasing rate of T{sub MI} for Dy, Ho, and Y materials is lower than that expected from the variation of T{sub MI} for the larger rare earth perovskites. This is probably related to the subtle monoclinic distortion found for Ho and Y nickelates. The high-resolution synchrotron X-ray powder patterns have revealed changes in the microstructure along the series. Powder patterns for orthorhombic RNiO{sub 3} (R = Sm, Eu, Gd, Dy) display asymmetric tails for some reflections which are due to structural mistakes such as stacking faults or regular intergrowths. These mistakes are not present in monoclinic RNiO{sub 3} (R = Ho, Y) nickelates.« less
  • (La{sub 1+x}Ca{sub 1-x})CoRuO{sub 6} double perovskites have been studied by neutron diffraction and x-ray absorption spectroscopy. The thermal evolution of the (LaCa)CoRuO{sub 6} structure has been investigated between 4 and 1073 K using neutron powder diffraction. The cell b axis shows a crossover from negative to positive thermal expansion at T{approx_equal}425 K, which is accompanied by a discontinuity in the c axis. This is shown to result from a partial orbital ordering of the Co{sup 2+} t{sub 2g} holes. Ru valence states of doped (La{sub 1+x}Ca{sub 1-x})CoRuO{sub 6} (-0.25{<=}x{<=}0.25) materials have been investigated using XANES spectroscopy. Electron-doping (x>0) leads tomore » reduction of Ru{sup 5+}{yields}Ru{sup 4+} while hole-doped x{<=}0 compositions have a constant Ru{sup 5+} state. These observations support a proposed asymmetric doping model.« less
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  • Structural characterization and electronic properties of the LaNi{sub 0.95}M{sub 0.05}O{sub 3} (M = Mo, W, Sb, Ti, Cu, Zn) perovskite-like system are reported. These compounds can be regarded as being derived from LaNiO{sub 3} by partial substitution of Ni{sup 3+} in this material by M{sup 6+}, M{sup 5+}, M{sup 4+}, or M{sup 2+} formal cations, with a partial reduction of Ni{sup 3+} to Ni{sup 2+} taking place. X-ray powder diffraction data were analyzed by means of the Rietveld method and show that all the title materials present perovskite-type structure with a rhombohedral (S.G. R{bar 3}c) or orthorhombic (S.G. Pbnm) symmetry,more » depending on the nature of the M cation. In all cases, Ni and M cations are placed at random in octahedral B-sites of perovskite structure. Electrical resistivity measurements (four probe method) show metal-to-insulator (M-I) transitions for M = Mo, W, Ti, Cu, Zn at temperatures of about 50K and a semiconductor behavior for the Sb sample in the whole temperature range explored. Magnetic susceptibility measurements show the presence of weak ferromagnetic interactions for M = Sb and Pauli paramagnetism for the remaining compounds.« less
  • Soft x-ray resonant scattering at the Ni L{sub 2,3} edges is used to test models of magnetic- and orbital-ordering below the metal-insulator transition in NdNiO{sub 3}. The large branching ratio of the L{sub 3} to L{sub 2} intensities of the (1/2 0 1/2) reflection and the observed azimuthal angle and polarization dependence originates from a noncollinear magnetic structure. The absence of an orbital signal and the noncollinear magnetic structure show that the nickelates are materials for which orbital ordering is absent at the metal-insulator transition.