Electron Spin Resonance Study on Room-Temperature Ferromagnetic La0.9Sr0.1MnO3 Nanoparticles.

Temperature-dependent electron spin resonance (ESR) is applied to investigate La0.9Sr0.1MnO3 nanoparticles incorporating with magnetization and electrical transport measurements. Ferromagnetism is observed at room temperature which is much higher than the TC value for bulk samples ( $\sim $ 150 K). The ESR analysis confirms the coexistence of multiple magnetic phases consistent with the field-dependent magnetization-temperature curves. By fitting ESR spectra, the room-temperature multiphases are identified as the mixture of ferromagnetic and paramagnetic states, similar to the Griffiths phase observed in bulk samples. The field-dependent resistivity shows colossal magnetoresistance effect up to room temperature. Based on our analysis, the size-effect-induced room-temperature ferromagnetism is strongly correlated with the enhancement of the Griffith phase separation temperature. [ABSTRACT FROM AUTHOR]