Visualizing high-temperature spin dynamics in La_1−xCa_xMnO₃from a mapping of EPR linewidth andg-factor

Abstract

We report the measurements of electron paramagnetic resonance (EPR) on powder samples of La 1-x Ca x MnO 3 at the commensurate carrier concentrations of x = N/8 (N = 1, 2, 3, 4, 5, 6, and 7) within temperature range 100K 450K T ≤ ≤. It is suggested that the mapping of EPR linewidth and g factor is a useful way to reveal the high-temperature spin dynamics in La 1-x Ca x MnO 3 . An electron-hole asymmetry can be clearly observed in the mapping of g factor. The linewidth ∆H as a function of x drops at x = 3/8 due to the mechanism of exchange narrowing. The activation energy ΔE obtained by fitting the intensity I to an Arrhenius law displays a sharp peak at x = 3/8, suggesting a strong ferromagnetic coupling. Our results convince that the spin-only relaxation mechanism should dominate the high-temperature paramagnetic regime in colossal magnetoresistance (CMR) manganites. PACS number(s): 75.47. Lx, 71.38.Ht

Ag-SiO2-Er2O3 Nanocomposites: Highly Effective Upconversion Luminescence at High Power Excitation and High Temperature

“…It can be seen that in bulk Er 2 O 3 , the EPR signal was not observed, while in Er 2 O 3 NPs, a EPR signal was detected in the range of 880–5580 Gauss with g factor about 1.9951. In general, when the actual measured g factor is lower than the free electron g factor (g free = 2.0023), the EPR signal represents the electron trap32. In other words, the EPR signal in Er 2 O 3 NPs is assigned to the oxygen defects.…”

Antiferromagnetic rare region effect in Pr0.5Ca0.5MnO3

“…1C, D). In order to understand the nature of these resonance peaks and to accurately calculate corresponding intensities, linewidth and resonance fields, we have fitted the ESR signals by the following equation [33,34]-…”

Comment on ‘Visualizing high-temperature spin dynamics in La1−xCaxMnO3from a mapping of EPR linewidth andgfactor’

“…A possible reason for this invalid conclusion may be an inadequate method of PM g factor extraction used by the authors. Thus, it seems useful to comment on this and some other points of [1].…”

“…Liu et al reported in their recent paper [1] data on electron paramagnetic resonance (EPR) measured for polycrystalline La 1−x Ca x MnO 3 (LCMO) manganites at the commensurate carrier concentrations of x = N/8 (N = 1, 2, 3, 4, 5, 6, and 7). Using numerical fittings of the EPR spectra (dP/dH ), where P is a microwave energy absorbed by the sample and H is an external magnetic field, they extracted the temperature (T ) and concentration dependences of the EPR signal linewidth H pp and g factor within the interval 100 K T 450 K. The temperature dependences of H pp and the EPR signal intensity (I ) were further discussed by the authors in the framework of known models [2][3][4][5][6] and they claimed, as a result of this analysis, that 'An electron-hole asymmetry can be clearly observed in the mapping of the g factor and linewidth H '.…”