Carrier-Controlled Ferromagnetism in SrTiO_{3}

Magnetotransport and superconducting properties are investigated for uniformly La-doped SrTiO_{3} films and GdTiO_{3}/SrTiO_{3} heterostructures, respectively. GdTiO_{3}/SrTiO_{3} interfaces exhibit a high-density 2D electron gas on the SrTiO_{3} side of the interface, while, for the SrTiO_{3} films, carriers are provided by the dopant atoms. Both types of samples exhibit ferromagnetism at low temperatures, as evidenced by a hysteresis in the magnetoresistance. For the uniformly doped SrTiO_{3} films, the Curie temperature is found to increase with doping and to coexist with superconductivity for carrier concentrations on the high-density side of the superconducting dome. The Curie temperature of the GdTiO_{3}/SrTiO_{3} heterostructures scales with the thickness of the SrTiO_{3} quantum well. The results are used to construct a stability diagram for the ferromagnetic and superconducting phases of SrTiO_{3}.