Anomalies of Elastic Properties at Phase Transitions in Rare Earth Cobaltites RBaCo<sub>4</sub>O<sub>7</sub> (R = Y, Er - Lu)

Abstract

Elastic properties of rare-earth cobaltites RBaCo4O7 (R = Y, Er - Lu) are studied in the temperature range (4.2 - 300) K. Significant softening of Youngs modulus for Lu-and Yb-cobaltites is found at temperature decrease, showing an instability of the crystal structure and accompanying by a reverse jump at the structural phase transition. Softening and jump at phase transition decrease more than by the order of value, while the transition temperature Ts and hysteresis dTs enlarge from Lu-to Tm-and Er-compounds. Smooth and weak elastic anomaly at the magnetic phase transition is found resulting from low dimension and frustration of exchange interactions in the Co subsystem in most of the rare-earth cobaltites studied.