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Title: The frustrated fcc antiferromagnet Ba 2 YOsO 6: Structural characterization, magnetic properties and neutron scattering studies

Here we report the crystal structure, magnetization, and neutron scattering measurements on the double perovskite Ba 2 YOsO 6. The Fm$$\bar{3}$$m space group is found both at 290 K and 3.5 K with cell constants a 0=8.3541(4) Å and 8.3435(4) Å, respectively. Os 5+ (5d 3) ions occupy a nondistorted, geometrically frustrated face-centered-cubic (fcc) lattice. A Curie-Weiss temperature θ ~₋700 K suggests the presence of a large antiferromagnetic interaction and a high degree of magnetic frustration. A magnetic transition to long-range antiferromagnetic order, consistent with a type-I fcc state below T N~69 K, is revealed by magnetization, Fisher heat capacity, and elastic neutron scattering, with an ordered moment of 1.65(6) μ B on Os 5+. The ordered moment is much reduced from either the expected spin-only value of ~3 μ B or the value appropriate to 4d 3 Ru 5+ in isostructural Ba 2 YRuO 6 of 2.2(1) μ B, suggesting a role for spin-orbit coupling (SOC). Triple-axis neutron scattering measurements of the order parameter suggest an additional first-order transition at T=67.45 K, and the existence of a second-ordered state. We find time-of-flight inelastic neutron results reveal a large spin gap Δ~17 meV, unexpected for an orbitally quenched, d 3 electronic configuration. In conclusion, we discuss this in the context of the ~5 meV spin gap observed in the related Ru 5+,4d 3 cubic double perovskite Ba 2YRuO 6, and attribute the ~3 times larger gap to stronger SOC present in this heavier, 5d, osmate system.
Authors:
 [1] ;  [2] ;  [3] ;  [1] ;  [4] ;  [4] ;  [5] ;  [6] ;  [6] ;  [7] ;  [8]
  1. McMaster Univ., Hamilton, ON (Canada). Dept. of Physics and Astronomy
  2. McMaster Univ., Hamilton, ON (Canada). Dept. of Physics and Astronom
  3. McMaster Univ., Hamilton, ON (Canada). Dept. of Chemistry
  4. Univ. of Manitoba, Winnipeg, MB (Canada)
  5. Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States). Neutron Data Analysis and Visualization Division
  6. Atomic Energy of Canada (AECL), Limited, Chalk River, ON (Canada). Canadian Neutron Beam Centre
  7. McMaster Univ., Hamilton, ON (Canada). Dept. of Physics and Astronomy; Brockhouse Inst. for Materials Research, Hamilton, ON (Canada); Canadian Inst. for Advanced Research, Toronto, ON (Canada)
  8. McMaster University
Publication Date:
Grant/Contract Number:
AC05-00OR22725
Type:
Accepted Manuscript
Journal Name:
Physical Review. B, Condensed Matter and Materials Physics
Additional Journal Information:
Journal Volume: 91; Journal Issue: 7; Journal ID: ISSN 1098-0121
Publisher:
American Physical Society (APS)
Research Org:
Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States). Spallation Neutron Source (SNS)
Sponsoring Org:
USDOE Office of Science (SC), Basic Energy Sciences (BES) (SC-22)
Country of Publication:
United States
Language:
English
Subject:
36 MATERIALS SCIENCE
OSTI Identifier:
1185738
Alternate Identifier(s):
OSTI ID: 1180011