Temperature dependence of the conductance and magnetoresistance of CrO2 powder compacts -: art. no. 064410

CrO2 cold-pressed powder compacts show different electronic transport property than the single crystals. We have analyzed the temperature dependence of the conductance and magnetoresistance (MR) of cold-pressed compacts of CrO2 powders. Our results show that there exist two channels of the conductance G. One is the inter-granular spin-dependent tunneling conductance (G(SDT)), which is found proportional to exp(-1/T-1/2). The other is a spin-independent channel (G(SI)) due to the higher-order inelastic hopping through the localized states due to imperfections in the barrier. G(SI) is found to follow the power law T-gamma and gamma is related to the number of localized states in the barrier. At low temperatures the conductance is determined essentially by the SDT channel. As the temperature increases, the hopping channel becomes dominant. This spin-independent inelastic hopping conductance is one of the main reasons for the rapid decrease of MR with increasing temperature.