Behavior of Cobalt and Rare-Earth Subsystems in Frustrated Cobaltites DyBaCo4O7 + x
Structural, elastic, and magnetic properties of cobaltites DyBaCo4O7 + x produced by various technologies and distinguished by oxygen excess x are experimentally studied. It was found that rhombic distortion of the crystal structure of annealed stoichiometric samples with x = 0 results in frustration removal and elastic property anomalies in the TN region, caused by cobalt subsystem ordering. At an insignificant oxygen nonstoichiometry, no structural distortions occur in quenched samples, and anomalies in elastic characteristics in the TN region smooth and disappear. The studies of DyBaCo4O7 + x magnetic properties show that the rare-earth (RE) subsystem remains paramagnetic and its contribution exceeds the contribution of the Co-subsystem with strong antiferromagnetic couplings by an order of magnitude. The magnetic susceptibility of the stoichiometric sample does not exhibit an appreciable anomaly at TN, since cobalt subsystem ordering is not accompanied by the formation of a noticeable effective field on RE ions.
This study was supported in part by the grant of the Institute of Inorganic Chemistry within the State contract of the Federal Agency for Scientific Organizations of the Russian Federation (subject 45.22 no. 0082-2018-0003, АААА-А18-118012390045-2).