Electron paramagnetic resonance study of (La0.33Sm0.67)0.67Sr0.33−xBaxMnO3 (x<0.1): Griffiths phase

Manganite compounds (La0.33Sm0.67)0.67Sr0.33−xBaxMnO3 with light Ba doping (x=0.01-0.09) have been investigated by electron paramagnetic resonance over the temperature range 110-450 K. It was found that the EPR linewidth behavior changed drastically in samples with these low Ba concentrations. For all the samples there was observed coexistence of paramagnetic and ferromagnetic phases below the phase-transition (Curie) temperature. EPR signals characteristic of a Griffiths phase were observed in the samples with x=0.03, 0.06, and 0.09. The temperature dependence of EPR linewidth in the paramagnetic phase was analyzed on the basis of the variable-range-hopping model, which explained the observed data.