Large positive magnetoresistance of the lightly doped La2CuO4 Mott insulator

The in-plane and out-of-plane magnetoresistance (MR) of single crystals of La2CuO4, lightly doped (x=0.03) with either Sr (La2-xSrxCuO4) or Li (La(2)Cu(1-x)LixO(4)), have been measured in the fields applied parallel and perpendicular to the CuO2 planes. Both La1.97Sr0.03CuO4 and La2Cu0.97Li0.03O4 exhibit the emergence of a positive MR at temperatures (T) well below the spin glass 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.