Electron spin resonance analysis of magnetic structures in La2/3Ca1/3MnO3

Measurements of electron spin resonance (ESR) of La2/3Ca1/3MnO3 (LCMO) in the ferromagnetic and paramagnetic phases were carried out. Phase transition and temperature dependence of the peak-to-peak ESR linewidth were determined. The transition temperature between ferromagnetic and paramagnetic phases was observed at 265 K. A prominent increase of the peak-to-peak linewidth with decreasing temperature below Tc was observed. Using the dynamic scale theory and block spin transformation in critical phenomenon, the quantitative calculation of peak-to-peak linewidth at near Tc was made, which was in good agreement with the experimental data. It was believed that the long interactions between the ferromagnetic microregions for LCMO played a key role in determining the ESR linewidth.