Pressure-Induced Negative-Positive Magnetoresistance Crossover Near Metal-Insulator Transition in La_{0.8}Ag_{0.1}MnO_{3}

We investigated the effect of high pressure on the field dependences of magnetoresistance (MR) in La_{0.8}Ag_{0.1}MnO_{3} near the metal-insulator transition temperature. Our results showed that an increase in pressure results in a decrease in the magnitude of negative MR. At pressures $P\geqslant5.6$ GPa and magnetic fields up to 4 kOe, we observed a positive MR. However, with a further increase in magnetic field (>4 kOe), the MR again became negative. Therefore, we discovered a "negative-positive" MR crossover induced by high pressure near the transition temperature. We supported our experimental findings with a qualitative theoretical interpretation using the electron-hole model of MR. This theory explains observed the MR sign change.