{'fraction_non_alphanumeric': 0.07402234636871509, 'fraction_numerical': 0.02653631284916201, 'mean_word_length': 5.230434782608696, 'pattern_counts': {'":': 0, '<': 0, '<?xml version=': 0, '>': 0, 'https://': 0, 'lorem ipsum': 0, 'www.': 0, 'xml': 0}, 'pii_count': 0, 'substrings_counts': 0, 'word_list_counts': {'cursed_substrings.json': 0, 'profanity_word_list.json': 0, 'sexual_word_list.json': 0, 'zh_pornsignals.json': 0}}
Phase stability and low-temperature specific heat up to 14 T of BaCuOx as a function of oxygen stoichiometry.

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.