Electron spin resonance study of colossal magnetoresistive materials La 0.7Ba 0.3Mn 1- xFe xO 3 ( x=0.08-0.2)

Electron spin resonance (ESR) was carried out on the La _0.7Ba _0.3Mn _{1- x}Fe _xO ₃ ( x=0.08-0.2) compounds over the temperature range of 100-300 K. We observed that the temperature dependence of the EPR spectra has a phase separation phenomenon below T_C for x=0.08-0.15 samples. Phase transition and temperature dependence of ESR, g_eff value, linewidth, and intensity were determined. The g-value increases gradually with decrease in temperature in the paramagnetic state. The activation energies obtained from the temperature dependence of resonance intensity and linewidth are smaller in the Fe-doped sample. The ferromagnetic spin correlations would be significantly weakened by partially substituting the Mn with Fe.