Phase transitions in frustrated ErBaCo4O7 + x (x = 0–0.06) cobaltites at a small deviation from stoichiometryстатья
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Дата последнего поиска статьи во внешних источниках: 12 января 2022 г.
Аннотация:The structural (lattice metric) and elastic characteristics of ErBaCo4O7 + x cobaltites, which aresubjected to different heat treatment and are characterized by a low excess oxygen content x, are experimentallystudied in the region of structural and magnetic phase transitions. During the structural transition in astoichiometric ErBaCo4O7 sample annealed in vacuum, parameter Δa/a does not exhibit specific featuresand parameters b and c undergo jumps of different signs and magnitudes, Δb/b ≈ 4 × 10–3 and Δc/c ≈ –5 ×10–3. This behavior leads to jumps in the anisotropic (orthorhombic, εo ≈ –4 × 10–3) and isotropic (volumetric,ΔV/V ≈ –1 × 10–3) deformations. At a slight deviation from oxygen stoichiometry, the character of structuraldistortion changes: the magnitude of the anisotropic deformation and the sign of the isotropic deformationchange. The structural distortion in the stoichiometric sample is accompanied by a sharp jump inYoung’s modulus (8 × 10–2), and the elastic anomalies in the TS range in weakly stoichiometric samples withx ~ 0.03 decrease by an order of magnitude. A comparison of the elastic anomalies in the magnetic phase transitiontemperature TN range for distorted samples with various deviations from stoichiometry indicates thatthe formation of a long-range magnetic order in the cobalt subsystem is likely to be influenced by both astructural distortion and the nonstoichiometric-oxygen-induced disorder.