Physics

Intrinsic Origins

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Science  20 Jul 2012:
Vol. 337, Issue 6092, pp. 271
DOI: 10.1126/science.337.6092.271-a

Interfacing two unlike materials may give rise to unexpected properties resulting from the asymmetry of the structure. Such is the case in two-dimensional interfaces of perovskite oxide films; in the best-known example of the LaAlO3/SrTiO3 (LAO/STO) interface, ferromagnetism has been observed even though neither of the two materials is magnetic in the bulk. This and other interface effects are thought to originate from STO, but whether they are an intrinsic property of the electron liquid in STO is not known. Moetakef et al. study the magnetism in STO using two systems: GdTiO3/STO heterostructures and La-doped STO films; in both cases, STO is doped with carriers, from the interface or the La dopants, respectively. The authors observe ferromagnetism in both systems, and superconductivity coexisting with magnetism in the doped films. The ferromagnetic Curie temperature increases strongly with the carrier density measured through the Hall effect, and the data from the two systems fall onto the same curve, indicating universal dependence and an intrinsic mechanism.

Phys. Rev. X 2, 021014 (2012).

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