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Title: Nature of lattice distortions in the cubic double perovskite Ba 2 NaOsO 6

In this paper, we present detailed calculations of the electric field gradient (EFG) using a point charge approximation in $${\mathrm{Ba}}_{2}{\mathrm{NaOsO}}_{6}$$, a Mott insulator with strong spin-orbit interaction. Recent $$^{23}\mathrm{Na}$$ nuclear magnetic resonance (NMR) measurements found that the onset of local point symmetry breaking, likely caused by the formation of quadrupolar order [Chen, Pereira, and Balents, Phys. Rev. B 82, 174440 (2010)], precedes the formation of long range magnetic order in this compound [Lu et al., Nat. Commun. 8, 14407 (2017); Liu et al., Physica B 536, 863 (2018)]. An extension of the static $$^{23}\mathrm{Na}$$ NMR measurements as a function of the orientation of a 15 T applied magnetic field at 8 K in the magnetically ordered phase is reported. Broken local cubic symmetry induces a nonspherical electronic charge distribution around the Na site and thus finite EFG, affecting the NMR spectral shape. We combine the spectral analysis as a function of the orientation of the magnetic field with calculations of the EFG to determine the exact microscopic nature of the lattice distortions present in low temperature phases of this material. Finally, we establish that orthorhombic distortions, constrained along the cubic axes of the perovskite reference unit cell, of oxygen octahedra surrounding Na nuclei are present in the magnetic phase. Other common types of distortions often observed in oxide structures are considered as well.
Authors:
 [1] ;  [1] ;  [2] ;  [3] ;  [1]
  1. Brown Univ., Providence, RI (United States). Dept. of Physics
  2. National High Magnetic Field Lab., Tallahassee, FL (United States)
  3. Stanford Univ., CA (United States). Dept. of Applied Physics. Geballe Lab. for Advanced Materials; SLAC National Accelerator Lab., Menlo Park, CA (United States). Stanford Inst. for Materials and Energy Sciences
Publication Date:
Grant/Contract Number:
AC02-76SF00515; DMR-1608760; DMR95-27035
Type:
Accepted Manuscript
Journal Name:
Physical Review B
Additional Journal Information:
Journal Volume: 97; Journal Issue: 22; Journal ID: ISSN 2469-9950
Publisher:
American Physical Society (APS)
Research Org:
SLAC National Accelerator Lab., Menlo Park, CA (United States); Brown Univ., Providence, RI (United States); National High Magnetic Field Lab., Tallahassee, FL (United States); Stanford Univ., CA (United States)
Sponsoring Org:
USDOE Office of Science (SC), Basic Energy Sciences (BES) (SC-22); National Science Foundation (NSF)
Country of Publication:
United States
Language:
English
Subject:
36 MATERIALS SCIENCE; crystal phenomena; magnetic anisotropy; phase transitions; phase transitions by order; spin-orbit coupling; structural properties
OSTI Identifier:
1457776