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Large Positive Magnetoresistance of the Lightly Doped La_{2}CuO_{4} Mott Insulator

The in-plane and out-of-plane magnetoresistance (MR) of single crystals of La_2CuO_4, lightly doped (x=0.03) with either Sr (La_{2-x}Sr_xCuO_4) or Li (La_2Cu_{1-x}Li_xO_4), have been measured in the fields applied parallel and perpendicular to the CuO_2 planes. Both La_{1.97}Sr_{0.03}CuO_4 and La_2Cu_{0.97}Li_{0.03}O_4 exhibit the emergence of a positive MR at temperatures (T) well below the spin glass (SG) transition temperature T_{sg}, where charge dynamics is also glassy. This positive MR grows as T->0 and shows hysteresis and memory. In this regime, the in-plane resistance R_{ab}(T,B) is described by a scaling function, suggesting that short-range Coulomb repulsion between two holes in the same disorder-localized state plays a key role at low T. The results highlight similarities between this magnetic material and a broad class of well-studied, nonmagnetic disordered insulators.