Crystal structures, frustrated magnetism, and chemical pressure in Sr-doped Ba3NiSb2O9 perovskites

Mélanie Viaud, Catherine Guillot-Deudon, Eric Gautron, Maria Teresa Caldes, Guido Berlanda, Philippe Deniard, Philippe Boullay, Florence Porcher, Carole La, Céline Darie, A. Zorko, A. Ozarowski, Fabrice Bert, Philippe Mendels, and Christophe Payen
Phys. Rev. Materials 6, 124408 – Published 20 December 2022

Abstract

The effects of chemical pressure on the structural and magnetic properties of the triple perovskite Ba3NiSb2O9 are investigated by substituting Sr2+ ions for Ba2+ ions. Two Ba3xSrxNiSb2O9 phases could be stabilized via a solid-state reaction at ambient pressure (AP) in air. The 6H with Sb2O9 pairs (x=0)6H with NiSbO9 pairs (x=0.5)3C (cubic with corner-sharing octahedral, x=1.25) sequence of structural phases occurs with increasing Sr content, i.e., chemical pressure, which is like that previously reported for pure samples of Ba3NiSb2O9 obtained under increasing high physical pressure (HP). For the 6H Ba2.5Sr0.5NiSb2O9 (x=0.5) phase, using combined Rietveld refinements of powder x-ray and neutron diffraction patterns, precession electron diffraction tomography data collected on thin crystals, aberration-corrected high-angle annular dark field scanning transmission electron microscopy coupled to energy dispersive x-ray spectroscopy mapping, we reach the conclusion that the structure features corner-sharing SbO6 octahedra and NiSbO9 pairs of face-shared octahedra (or Ni-Sb dumbbells) with either a random orientation of the Ni-Sb dumbbells or nanosized chemical correlations for the dumbbell arrangement. As observed in HP Ba3NiSb2O9 produced through synthesis at 9 GPa, AP Ba1.75Sr1.25NiSb2O9 (x=1.25) crystallizes in a 3C double perovskite A2BBO6 cubic structure where A, B, and B sites are occupied by (Ba + Sr), Sb, and (23Ni+13Sb) atoms, respectively. The B sites, which are randomly occupied by spin-1 Ni2+ and diamagnetic Sb5+, form a face-centered-cubic (FCC) sublattice where the Ni2+ amount stays above the site percolation threshold. Weiss temperatures (65 and 213 K for Ba2.5Sr0.5NiSb2O9 and Ba1.75Sr1.25NiSb2O9, respectively) indicate that dominant magnetic interactions between Ni2+ spins are antiferromagnetic with magnitudes like those observed in the corresponding HP phases of pure Ba3NiSb2O9. As for the 6H HP Ba3NiSb2O9 compound, in 6H Ba2.5Sr0.5NiSb2O9, muon spin relaxation (μSR) measurements identify a dynamic magnetic state down to the base temperature (95 mK), consistent with a previously published inelastic neutron scattering study. For 3C Ba1.75Sr1.25NiSb2O9, μSR and Sb121 nuclear magnetic resonance measurements both indicate the presence of a transition to a static magnetic state below 11(1) K with a significant amount of disorder in this frozen state, in contrast to the spin-liquid state previously suggested for the 3C HP phase of Ba3NiSb2O9. Consistently, a broad maximum is observed in the specific heat at the same temperature. Building on the structural data, the magnetic properties of HP 6H Ba3NiSb2O9 and AP 6H Ba2.5Sr0.5NiSb2O9 are discussed in light of recent works on triangular and J1J2 honeycomb systems with or without quenched disorder. We are led to the conclusion that the driving force toward a spin-liquid-like state is quenched disorder which needs to be incorporated in J1J2 honeycomb models. Our evidence of a magnetic transition to a frozen magnetic ground state for the AP Sr-doped 3C phase is in line with models for geometrically frustrated FCC antiferromagnets. This calls for a better experimental and possibly theoretical understanding of the HP 3C phase.

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  • Received 3 June 2022
  • Accepted 16 November 2022

DOI:https://doi.org/10.1103/PhysRevMaterials.6.124408

©2022 American Physical Society

Physics Subject Headings (PhySH)

Condensed Matter, Materials & Applied Physics

Authors & Affiliations

Mélanie Viaud1, Catherine Guillot-Deudon1, Eric Gautron1, Maria Teresa Caldes1, Guido Berlanda2, Philippe Deniard1, Philippe Boullay3, Florence Porcher4, Carole La5, Céline Darie6, A. Zorko7,8, A. Ozarowski9, Fabrice Bert2, Philippe Mendels2,*, and Christophe Payen1,†

  • 1Nantes Université, CNRS, Institut des Matériaux de Nantes Jean Rouxel, IMN, F-44000 Nantes, France
  • 2Laboratoire de Physique des Solides, Université Paris-Saclay, CNRS, 91405 Orsay, France
  • 3CRISMAT laboratory, UMR6508, Normandie University, ENSICAEN, UNICAEN, CNRS, Caen 14050 France
  • 4Laboratoire Léon Brillouin, CEA Saclay, CNRS UMR12, F-91191 Gif-sur-Yvette, France
  • 5Nantes Université, CNRS, UMR 6112, Laboratoire de Planétologie et Géosciences, F-44000 Nantes, France
  • 6Université Grenoble Alpes, CNRS, Grenoble INP, Institut Néel, 38000 Grenoble, France
  • 7Jožef Stefan Institute, Jamova c. 39, 1000 Ljubljana, Slovenia
  • 8Faculty of Mathematics and Physics, University of Ljubljana, Jadranska u. 19, 1000 Ljubljana, Slovenia
  • 9National High Magnetic Field Laboratory, Florida State University, Tallahassee, Florida 32310, USA

  • *philippe.mendels@universite-paris-saclay.fr
  • christophe.payen@cnrs-imn.fr

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Vol. 6, Iss. 12 — December 2022

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