Effect of oxygen nonstoichiometry on magnetic phase transitions in frustrated cobaltites YB_aCo₄O_7+x (x = 0, 0.1, 0.2)

Abstract

Experimental studies were carried out for structural and elastic properties of cobaltites YBaCo4O7+x (x = 0, 0.1, 0.2) obtained by various technologies and distinguished by oxygen content. Correlation was revealed between the structure distortion at room temperature and a hysteresis in a ΔE(T)/T0 curve in the temperature range 80 – 280 K, as well as the anomaly value in the region of TN. It was found, that small deviations from stoichiometry (x = 0.1, 0.2) result in suppression of structural transition, reduce a hysteresis, quickly smooth out and reduce anomalies of the Young’s modulus ΔE(T)/T0 in the range of magnetic phase transition. This behavior indicates that structural and magnetic transitions are suppressed in nonstoichiometric samples and only short range correlations of order parameters are retained