The elastic, magnetic, and electrical properties of Sr1–уYуCoO3–x cobaltites in the composition range 0.2 ≤ y ≤ 0.3

Abstract

Anion-deficient layered cobaltites Sr0.75Ln0.25CoO3–x (Ln is a lanthanide) have attracted the special attention of the scientists who study the nature of phase transformations in perovskite-like cobaltites, the anomalous behavior of the temperature magnetization of which is still the subject of scientific discussion. The purpose of this work is to investigate the regularity of changes in the elastic, magnetic, and electrical properties of layered cobaltites Sr1–уYуCoO3–x in the composition range 0.2 ≤ y ≤ 0.3 over a wide temperature range. The studied polycrystalline samples were obtained by the known ceramic technology in the air. Electron microscopic studies were performed on a LEO 1455 PV scanning electron microscope. The temperature dependence of the Young’s modulus was studied by the method of resonance vibrations in the frequency range 1000–6000 Hz and in the temperature range 100–450 K. X-ray phase analysis was performed on a DRON-3M diffractometer under Cu-Kα radiation. Magnetic measurements were performed using a physical property measurement system (Cryogenic Ltd.) in the temperature range 5–325 K. As a result of the studies, it was found that in the temperature range 25–300 K, Sr1–уYуCoO3–x solid solutions (0.2 ≤ y ≤ 0.3) are characterized by the semiconductor-like conductivity. No significant magnetoresistive effect was observed in this temperature range for the studied compositions. It was shown that the Sr1–уYуCoO3–x solid solution (у = 0.25) exhibits two magnetic phase transformations: low-temperature near 220 K and high-temperature at 350 K. The nearby compositions of the concentration range 0.2 ≤ y ≤ 0.3 exhibit magnetic phase transformations at temperatures above room temperature. No low-temperature phase transitions were detected in them. It has been established that magnetic phase transformations are accompanied by structural transitions at corresponding temperatures.