Phase stability and low-temperature specific heat up to 14 T of BaCuO{sub {ital x}} as a function of oxygen stoichiometry
- Departement de Physique de la Matiere Condensee, Universite de Geneve, 24 quai Ernest-Ansermet, CH-1211 Geneve 4 (Switzerland)
The stability of the BaCuO{sub {ital x}} ({ital x}{ge}2) phase has been mapped over a wide range of temperature (300--1100 {degree}C) and oxygen pressure (10{sup {minus}5}--10{sup 3} bar). At ambient pressure and temperature, BaCuO{sub {ital x}} is found to be in a metastable state: long annealing at 450 {degree}C tends to decompose the phase into Ba{sub 2}Cu{sub 3}O{sub 5} and BaO{sub 2}. Having obtained the phase stability domain in the [{ital T},{ital p}(O){sub 2}] plane we were able to prepare single-phase samples of BaCuO{sub {ital x}} with different oxygen contents suitable for precise intrinsic thermodynamical measurements. We show that the behavior of the low-temperature specific heat (1.1{le}{ital T}{le}32 K) and its dependence on the magnetic field (0{le}{ital B}{le}14 T) may be understood by taking into account a many-level magnetic system directly related to the Cu{sub 6}O{sub 12} and Cu{sub 18}O{sub 24} structural blocks of BaCuO{sub {ital x}}. Depending on the oxygen concentration, competition between antiferromagnetic (AF) ordering and the many-level system is observed. With increasing oxygen content, the Neel temperature decreases whereas amplitude of the many-level system increases. The zero-field AF transition belongs to the three-dimensional isotropic Heisenberg universality class.
- OSTI ID:
- 122315
- Journal Information:
- Physical Review, B: Condensed Matter, Vol. 52, Issue 17; Other Information: PBD: 1 Nov 1995
- Country of Publication:
- United States
- Language:
- English
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