Coexistence of spin-lattice and spin-spin relaxation mechanism in perovskite manganite (La0.5Pr0.5)0.67Ca0.33MnO3

Abstract

Electron paramagnetic resonance (EPR) was applied extensively to probe the phase separation and spin relaxation mechanism in the perovskite manganites. In this study, we conducted the measurement of EPR for the perovskite manganites (La0.5Pr0.5)0.67Ca0.33MnO3. We found that both paramagnetic and ferromagnetic resonance peaks simultaneously emerged on resonance spectrum near below TC, exhibiting a typical characteristic of phase separation. The linewidth of EPR spectrum progressively enlarged upon the rising of temperature in the temperature range of T>TC and a quasilinear variation of peak-peak width was observed at TC<T<500 K. In contrast to the usual beliefs that the variation of peak-peak linewidth can be understood either by spin-lattice relaxation or by spin-spin relaxation, however, the linewidth behavior observed here shows a coexistence of two spin relaxation mechanisms. We proposed that the inhomogeneous electronic phases due to the intrinsic self-organizing growth were responsible for the appearance of multiple spin exchange interactions and variational relaxation mechanism. This finding would be possible to pave a new way for further investigating magnetic correlations and spin dynamics in the paramagnetic hole-doped manganites.