Pouya Moetakef, James R. Williams, Daniel G. Ouellette, Adam Kajdos, David Goldhaber-Gordon, S. James Allen, Susanne Stemmer
Magnetotransport and superconducting properties are investigated for uniformly La-doped SrTiO3 films and GdTiO3/SrTiO3 heterostructures, respectively. GdTiO3/SrTiO3 interfaces exhibit a high-density two-dimensional electron gas on the SrTiO3-side of the interface, while for the SrTiO3 films carriers are provided by the dopant atoms. Both types of samples exhibit ferromagnetism at low temperatures, as evidenced by a pronounced hysteresis in the magnetoresistance. For the uniformly doped SrTiO3 films, the Curie temperature is found to increase with carrier concentration and to coexist with superconductivity for carrier concentrations on the high-density side of the superconducting dome. The Curie temperature of the GdTiO3/SrTiO3 heterostructures scales with the thickness of the SrTiO3 quantum well, which determines the three-dimensional carrier concentrations in the well. The results are used to construct a phase stability diagram for the ferromagnetic and superconducting phases of SrTiO3.
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http://arxiv.org/abs/1204.1081
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