Structural properties and high-temperature spin and electronic transitions in GdCoO3: Experiment and theory

Тип публикации: статья из журнала

Год издания: 2013

Идентификатор DOI: 10.1103/PhysRevB.88.235105

Аннотация: We have investigated the x-ray diffraction (XRD) structure, magnetic susceptibility, and heat capacity of GdCoO3 in a wide temperature range. A model of phase separation of the low-spin (LS) and high-spin (HS) states has been proposed based on the analysis of XRD peak shape anomalies in the temperature range 200-800 K. From magnetic measurements we separated the HS Co3+ contribution and fitted it with the temperature-dependent spin gap. We found a smooth LS-HS crossover at T = 800 K. The possible contribution of the intermediate spin (IS) state to the thermodynamics is excluded by the calculation IS-LS excitation energy within the modified crystal-field approach. In the two-phase model, with HS/LS probabilities calculated from the found spin gap and the LS and HS volumes calculated by the DFT-GGA method, we were able to reproduce the temperature dependence of the unit-cell volume and thermal expansion. Thus, we conclude that in GdCoO3 the main mechanism of the lattice expansion is not the conventional lattice anharmonicity, but the HS/LS fluctuations. The electronic structure has been calculated by the LDA+GTB method. At zero temperature, we have obtained the charge-transfer insulator with the charge gap E-g = 0.5 eV. The thermal population of the HS term results in the in-gap band formation inside the insulator gap and smooth insulator-metal transition at T-IMT = 780 K. Heat-capacity measurements revealed a smooth maximum near the T-IMT.

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Издание

Журнал: PHYSICAL REVIEW B

Выпуск журнала: Vol. 88, Is. 23

ISSN журнала: 10980121

Место издания: COLLEGE PK

Издатель: AMER PHYSICAL SOC

Авторы

  • Orlov Y.S. (Siberian Federal University)
  • Vereshchagin S.N. (Institute of Chemistry and Chemical Technology,Siberian Branch,Russian Academy of Sciences)
  • Shishkina N.N. (Institute of Chemistry and Chemical Technology,Siberian Branch,Russian Academy of Sciences)
  • Perov N.S. (Faculty of Physics,M.V. Lomonosov Moscow State University)
  • Lamonova K.V. (O.O. Galkin Donetsk Institute for Physics and Engineering,National Academy of Sciences of Ukraine)
  • Babkin R.Y. (O.O. Galkin Donetsk Institute for Physics and Engineering,National Academy of Sciences of Ukraine)
  • Pashkevich Y.G. (O.O. Galkin Donetsk Institute for Physics and Engineering,National Academy of Sciences of Ukraine)
  • Dudnikov V.A. (L.V. Kirensky Institute of Physics,Siberian Branch,Russian Academy of Sciences)
  • Fedorov A.S. (Siberian Federal University)
  • Kazak N.V. (L.V. Kirensky Institute of Physics,Siberian Branch,Russian Academy of Sciences)
  • Voronov V.N. (L.V. Kirensky Institute of Physics,Siberian Branch,Russian Academy of Sciences)
  • Ovchinnikov S.G. (M.F. Reshetnev Siberian State Aerospace University)
  • Kuzubov A.A. (Siberian Federal University)
  • Anshits A.G. (Institute of Chemistry and Chemical Technology,Siberian Branch,Russian Academy of Sciences)
  • Solovyov L.A. (Institute of Chemistry and Chemical Technology,Siberian Branch,Russian Academy of Sciences)

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