Behavior of cobalt and rare-earth subsystems in frustrated cobaltites DyBaCo$_{4}$O$_{7+x}$

Structural, elastic, and magnetic properties of cobaltites DyBaCo$_{4}$O$_{7+x}$ 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 $T_N$ 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 $T_N$ region smooth and disappear. The studies of DyBaCo$_{4}$O$_{7+x}$ 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 $T_N$, since cobalt subsystem ordering is not accompanied by the formation of a noticeable effective field on RE ions.