We discovered nanoscale patches of magnetism coexisting with superconductivity at the interface between two non-magnetic insulating oxides, specifically LaAlO3 (LAO) grown on a SrTiO3 (STO) substrate. Both of these materials are band insulators and do not conduct electricity, but when LAO is grown on an STO substrate the interface where the two layers meet becomes metallic and even goes superconducting, allowing current to flow with no resistance, at temperatures lower than one tenth of a kelvin. The discovery of magnetism in these materials was surprising not only because the parent compounds are nonmagnetic, but also because magnetic fields do not usually coexist with superconductivity. The presence of magnetism in these complex oxide heterostructures opens exciting possibilities for engineering new materials as well as studying the interplay of the normally incompatible states of superconductivity and magnetism.

The image shows the ferromagnetic domains we discovered in this material.

Julie A. Bert, Beena Kalisky, Christopher Bell, Minu Kim, Yasuyuki Hikita, Harold Y. Hwang, and Kathryn A. Moler, Nature Physics 7 2079 (2011). Full Text

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