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

J.-Y. Genoud, A. Mirmelstein, G. Triscone, A. Junod, and J. Muller
Phys. Rev. B 52, 12833 – Published 1 November 1995
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Abstract

The stability of the BaCuOx (x≥2) phase has been mapped over a wide range of temperature (300–1100 °C) and oxygen pressure (105103 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.

  • Received 8 May 1995

DOI:https://doi.org/10.1103/PhysRevB.52.12833

©1995 American Physical Society

Authors & Affiliations

J.-Y. Genoud, A. Mirmelstein, G. Triscone, A. Junod, and J. Muller

  • Département de Physique de la Matiére Condensée, Université de Genève, 24 quai Ernest-Ansermet, CH-1211 Genève 4, Switzerland

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Vol. 52, Iss. 17 — 1 November 1995

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