Nanometer size effects on magnetic order in La1−xCaxMnO3 (x = 0.5 and 0.6) manganites, probed by ferromagnetic resonance

The data on X-band ferromagnetic resonance (FMR) in the half and electron-doped La0.5Ca0.5MnO3 (Ca0.5) and La0.4Ca0.6MnO3 (Ca0.6) nano-crystals and bulk ceramics are reported. The FMR data for considered nano-samples appeared to be strongly different, reflecting a difference in their magnetic/electronic order. An enhancement of the FMR signal intensities is observed in both nano Ca0.5 and Ca0.6 as compared to those in bulk. The peak intensity of such signal in nano Ca0.5 exceeds about two orders of magnitude the corresponding value in nano Ca0.6. This finding evidences on the respective ferromagnetic like and charge ordered antiferromagnetic ground states in Ca0.5 and Ca0.6.