Visualizing high-temperature spin dynamics in La1−xCaxMnO3 from a mapping of EPR linewidth and g-factor

• Published in: Journal of physics. Condensed matter Vol. 19; no. 19; pp. 196213 - 196213 (12)
• Main Authors: Liu, Y, Wan, S L, Li, X G
• Format: Journal Article
• Language: English
• Published: Bristol IOP Publishing 16.05.2007; Institute of Physics
• Subjects: Condensed matter: electronic structure, electrical, magnetic, and optical properties; Electron paramagnetic resonance and relaxation; Exact sciences and technology; Magnetic properties and materials; Magnetic resonances and relaxations in condensed matter, mössbauer effect; Magnetotransport phenomena, materials for magnetotransport; Manganites; Physics; Phase diagrams; Commensurate phases; Line widths; Magnetic transitions; Small polaron; g-factor; Spin dynamics; High spin states; Ferromagnetism; Electron paramagnetic resonance; Carrier density; Exchange interactions; Manganites
• ISSN: 0953-8984; 1361-648X
• DOI: 10.1088/0953-8984/19/19/196213

We report the measurements of electron paramagnetic resonance (EPR) on powder samples of La1-xCaxMnO3 (LCMO) at the commensurate carrier concentrations of x = N/8 (N = 1,2,3,4,5,6, and 7) within the temperature range 100 K < =T < =450 K. It is found that the mapping of the EPR linewidth DeltaH and the g-factor shows an electron-hole asymmetry in the paramagnetic insulating regime of the LCMO phase diagram. The drop of linewidth DeltaH with decreasing temperature in the mapping resembles the contour of the ferromagnetic transition curve in the LCMO phase diagram, while the isothermal DeltaH becomes narrowest at x = 3/8 due to the predominant double exchange interaction. By comparing the small-polaron model with spin-spin relaxation mechanism, we demonstrate that the latter should dominate the paramagnetic insulating regime of the LCMO phase diagram.