Rare-earth cobaltates Dy0.5-xErxBa0.5CoO3 (x=0, 0.03 and 0.05) have been systematically investigated to elucidate the effect of Er substitution on elastic as well as magnetic and transport properties. DC electrical resistance and AC susceptibility measurements showed that the x=0 sample exhibited an insulating behavior and an anti-ferromagnetic (AFM) transition, TN at 198 K as well as ferromagnetic (FM) transition, TC at 260 K. Increasing of Er content suppressed the FM and AFM state suggestively due to the increase in size disorder arising from the size mismatch between A-site cations as shown from our calculation of variance σ(2). On the other hand, both absolute longitudinal and shear velocities and related elastic moduli measured at 210 K decreased with Er content in conjunction with the declining in the FM domain indicating a weakening in elastic properties. A longitudinal velocity anomaly characterized by a drop in velocity upon cooling before hardening with further cooling was observed for all samples. This abnormal elastic anomaly can be attributed due to the Jahn-Teller (JT) distortion of intermediate-spin Co(3+) ions. Analysis of the elastic anomaly using the mean-field theory suggested that it is related to the JT effect which transformed from dynamic to static type with decreasing temperature. The elastic anomaly shifted to lower temperature from 129 K (x=0) to 124 K (x=0.05) with Er substitution indicating a weakening of the static JT effect.
In electronic applications, good dielectric permittivity material has huge potential in the capacitive energy storage devices. Herein, in the present work the dielectric study of SrLaLiTe1-xMnxO6 (x = 0.02, 0.04, 0.06, 0.08, and 0.10) double perovskites has been studied and discussed. These compounds were prepared through solid-state reaction method. All of the prepared compounds were confirmed to crystallized in monoclinic structure of P21/n space symmetry with better crystallization when dopant concentrations increased until x = 0.08. The formation of Li-O-Te/Mn bonds in octahedral structures in all compounds were confirmed in this study. The existence of peaks at specific wavenumbers indicated vibrations of B-site cations' bonds. When dopant amounts were increased from x = 0.02 to x = 0.08, there was an increasing trend of grains sizes formation in the compounds. The discussions on effects of grain sizes towards dielectric properties were included in this paper. Other important results and discussions comprised of the significant effects of dopant on the optical band gap (Eopt) and absorption frequencies of the compounds. The decreasing trend of Eopt towards semiconductor range indicated the compounds' promising potentials for optoelectronic device application.