Study of magnetoresistance behavior near percolation threshold in CrO2/Fe3O4 binary half-metal composites

The electrical properties and magnetoresistance (MR) of CrO2/Fe3O4 composites with opposite spin polarization have been investigated as a function of CrO2 content. Experimental results indicate that the conductivity exhibits an abrupt increase when CrO2 volume fraction ϕ is close to 0.15, where a percolation behavior happens. Magnetoresistance measurement shows a minimum value in the vicinity of percolation threshold at a temperature of 77 K, while this phenomenon cannot be observed at 150 K. Due to spin-dependent tunneling through grain boundary, the reduction in MR at 77 K mainly results from the opposite sign of spin polarizations in the binary half-metal granular CrO2/Fe3O4 composite.