EPR Studies of Rare-Earth Manganites La0.7−xEuxSr0.3MnO3 (x = 0.1–0.7)

• Published in: Applied magnetic resonance Vol. 55; no. 9; pp. 1199 - 1219
• Main Authors: Yatsyk, I., Mamedov, D. V., Shestakov, A. V., Fazlizhanov, I. I., Eremina, R. M., Andronenko, S. I., Pyataev, A. V., Vadnala, S., Asthana, S., Misra, S. K.
• Format: Journal Article
• Language: English
• Published: Vienna Springer Vienna 01.09.2024; Springer Nature B.V
• Subjects: Atoms and Molecules in Strong Fields; Crystal structure; Curie temperature; Electron paramagnetic resonance; Electrons; Entropy; Europium; Ferromagnetic phases; Ferromagnetic resonance; Ferromagnetism; High temperature; Laser Matter Interaction; Magnetic fields; Manganites; Organic Chemistry; Original Paper; Perovskites; Phase transitions; Physical Chemistry; Physics; Physics and Astronomy; Rare earth elements; Room temperature; Solid State Physics; Spectroscopy/Spectrometry; Spectrum analysis; Superhigh frequencies; Working fluids
• ISSN: 0937-9347; 1613-7507
• DOI: 10.1007/s00723-024-01694-4

The Europium rare-earth manganites, La 0.7− x Eu x Sr 0.3 MnO 3 ( x  = 0.0–0.7), were investigated by the technique of X-band electron paramagnetic resonance (EPR) in the temperature range from 30 to 500 K. As the temperature was lowered, the various samples made transitions from paramagnetic to ferromagnetic phases. Furthermore, coexistence of anywhere from two to three ferromagnetic phases in the various samples was found. The third ferromagnetic phase was observed only in the samples with x  = 0.1, 0.2, 0.3. The Curie temperatures for the various samples were estimated from the characteristics of the variable-temperature EPR spectra. The EPR data indicated the presence of Griffiths phases in the samples with x  = 0.2, 0.3, 0.4, 0.5, 0.6, from which the respective Griffiths temperatures were determined. The activation energies were estimated here from the EPR data using the hopping model. The EPR linewidth behavior is found to be consistent with that predicted by the bottlenecked spin-relaxation model. The perovskite La 0.5 Eu 0.2 Sr 0.3 MnO 3 is potentially useful in the design of magnetocaloric refrigeration units as a working fluid, since its Curie temperature T C is found to be close to the room temperature. The various ferromagnetic components in the samples observed here have been resolved only by the technique of EPR, not possible by other techniques.