Synthesis and effect of Bi and ag substitutions on resistivity and magnetoresistance of (Lai.xBix)i.yAgyMn03 / Enera Entik David

The compound (Lai.xBix)i.yAgyMn03 (y=0.30, x = 0.05,0.10,0.20) was synthesized using solid state reaction technique. The transition from metallic behavior (T<Tmi) to insulating behavior (T>Tm) of resistivity as a function of temperature has been observed. When H=0T, the substitutions of Bi and Ag caused the peak resistivity p (0, TM1) to be decreased for jc=0.05-0.10. However, at x=0.20, the peak resistivity p(0, TMl) increased. This is probably due to increase in electrons localization as a result of Jahn-Teller effect. Under H=0.7T, the resistivity p (0.7, T) of all samples decreased if compared to at H=0T. This may due to spin of electrons are more aligned due to the external magnetic field. The highest MR of 28.5% was observed at x=0.05. The metallic part of resistivity region (T<Tmi) was best fitted to the model of electron-magnon scattering while the insulating region (7>7m) was fitted to the small polaron hopping model. The activation energy of 22 meV was obtained for all samples