Glassy ferromagnetism in La0.75Sr0.25-xKxCoO3 polycrystalline perovskite cobaltites

• Published in: Journal of electroceramics 2014-05, Vol.32 (2-3), p.224-229
• Main Authors: Mahfoudh, N., Koubaa, M., Cheikhrouhou-Koubaa, W., Cheikhrouhou, A.
• Format: Article
• Language: English
• Subjects: Ceramics; Characterization and Evaluation of Materials; Chemistry and Materials Science; Composites; Crystallography and Scattering Methods; Electrochemistry; Glass; Materials Science; Natural Materials; Optical and Electronic Materials
• ISSN: 1385-3449; 1573-8663
• DOI: 10.1007/s10832-013-9877-x

In this paper, the structural and magnetic properties of La 0.75 Sr 0.25-x K x CoO 3 (0≤x≤0.15) powder samples are reported. X-ray diffraction analysis using Rietveld refinement show that all our samples crystallize in the rhombohedral structure with R 3 ¯ c space group. At low temperatures, with increasing K amount, the samples change from ferromagnetic like behavior ( x  = 0, 0.05 and 0.1) to spin glass one ( x  = 0.15). The ferromagnetic-paramagnetic transition temperature decreases with increasing K amount from 235K ( x  = 0) to 200K ( x  = 0.1). In the paramagnetic phase, all our synthesized samples obey the Curie-Weiss law. In the vicinity of T C , the magnetic entropy change | ΔS M | for La 0.75 Sr 0.2 K 0.05 CoO 3 sample reached maximum values of 0.47Jkg/K and 2.27Jkg/K under magnetic field variation in the range 1T and 7T, respectively. The magnetization hysteresis loops demonstrate a weakening the ferromagnetism with increasing K content.