Inverse magnetoresistance in half-metallic granular mixture

The magnetoresistance (MR) of A/B granular mixture is investigated as a function of B content. A and B are both half-metallic materials, but have opposite spin polarization. The correlation of the angles between magnetic moments of neighboring grains is taken into account. Using Monte Carlo simulations, we model the granular mixture as a random resistor network. The variation of magnetoresistance with B content is calculated. The appearance of MR valley may be attributed to two kinds of materials with the opposite sign of spin polarizations. But in a granular mixture, little inverse magnetoresistance could be observed. Calculated results are consistent with the experiment as well. When there is a large difference between resistances of distinct contact barriers, a weak peak will appear in the magnetoresistance curve. Percolation effect is the probable origin of this weak peak.