The effect of Ho-doping and Ho-adding on electronic transport and magnetic properties of La0.67Ca0.33MnO3

The effect of Ho-doping and Ho-adding on the electronic transport and magnetic properties of melt-processed La0.67Ca0.33MnO3 (LCMO) is investigated by resistivity and AC susceptibility measurement. For Ho-addition of 1 mol% LCMO sample (Ho-LCM), its magnetic transition temperature Tc and metal-insulator (M-I) transition temperature Tp are enhanced about 70 K compared with Ho-free LCMO sample. However, for Ho-doping of 3 mol% LCMO sample (Ho-doping LCM), both Tc and Tp are reduced about 35 K. We give a reasonable explanation in terms of structural changes (bond distance and bond angle) gained from the XRD refinement. The nanoscale Ho distribution is consistent with the magnetic inhomogeneity induced MR which is verified by the double peaks in AC susceptibility χ'' and the drop of χ'(T) curve below Tc. The mechanism of transport of all the samples is discussed