Large magnetoresistance in spin- and carrier-doped SrTiO3

We studied SrTi O3 into which spins and carriers are doped by Cr substitution for Ti and La substitution for Sr, respectively. It was found that Weiss temperatures vary from negative to positive values with carrier doping, indicating the appearance of a ferromagnetic interaction between Cr spins via the conduction carriers. We also found negative magnetoresistance in these compounds, whose magnitude amounts to 70% at low temperatures. These results demonstrate that magnetic semiconductors with large magnetoresistance can be obtained based on conventional oxides, like SrTi O3, with independent doping of spins and carriers.