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Phase stability and low-temperature specific heat up to 14 T of x as a function of oxygen stoichiometry

Published in Physical Review. B, Condensed Matter. 1995, vol. 52, no. 17, p. 12833-12843
Abstract The stability of the BaCuOx (x≥2) phase has been mapped over a wide range of temperature (300–1100 °C) and oxygen pressure (10−5–103 bar). At ambient pressure and temperature, BaCuOx is found to be in a metastable state: long annealing at 450 °C tends to decompose the phase into Ba2Cu3O5 and BaO2. Having obtained the phase stability domain in the [T,p(O)2] plane we were able to prepare single-phase samples of BaCuOx with different oxygen contents suitable for precise intrinsic thermodynamical measurements. We show that the behavior of the low-temperature specific heat (1.1≤T≤32 K) and its dependence on the magnetic field (0≤B≤14 T) may be understood by taking into account a many-level magnetic system directly related to the Cu6O12 and Cu18O24 structural blocks of BaCuOx. Depending on the oxygen concentration, competition between antiferromagnetic (AF) ordering and the many-level system is observed. With increasing oxygen content, the Néel temperature decreases whereas amplitude of the many-level system increases. The zero-field AF transition belongs to the three-dimensional isotropic Heisenberg universality class.
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GENOUD, Jean-Yves et al. Phase stability and low-temperature specific heat up to 14 T of x as a function of oxygen stoichiometry. In: Physical Review. B, Condensed Matter, 1995, vol. 52, n° 17, p. 12833-12843. https://archive-ouverte.unige.ch/unige:93834

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Deposited on : 2017-04-25

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