Enhanced metal–insulator transition and magnetoresistance in melt-processed La0.67Ca0.33MnO3 and Ho-doped manganites

Abstract

We report significant enhancement of magnetoresistance (MR) in melt-processed La0.67Ca0.33MnO3 (LCM) and in Ho-doped LCM samples. The LCM system exhibits surprising enhancement of metal–insulator transition (TIM) that coincides with the Curie transition temperature (Tc), TIM≈Tc, illustrating the enhanced percolative transport and spin-polarization through grain boundaries. Surprisingly, 1 mol % of addition of Ho enhances Tc of ∼70 K with remarkable colossal MR. The nanoscale Ho distribution is consistent with the magnetic inhomogeneity-induced MR due to phase segregation in Ho-doped sample whereas charge-segregation picture is valid for undoped LCM.