Magnetotunneling properties are investigated by the research group of Prof. Suman Datta (Penn State) for a heterostructure tunnel junction between a Mott insulator (GdTiO₃) with ferromagnetic behavior and a nonferromagnetic band insulator (SrTiO₃). The complex-oxide heterostructure was synthesized using hybrid MBE by Prof. Susanne Stemmer’s group (UC Santa Barbara). The high density 2-D electron gas (2DEG) formed at the heterojunction shows ferromagnetic behavior at low temperature as evidenced by the hysteresis in the magnetotunneling current across the junction. A tunnel magnetoresistance of ~18% is achieved at 4K. Atomistic first-principles calculations by Prof. Datta’s group predict ferromagnetic behavior in the first interfacial monolayer of the 2DEG due to electron correlation.  A bias dependence, different from conventional ferromagnet / tunnel barrier / ferromagnet tunnel junctions, is shown to emerge from the energy dependent spin polarization of the 2DEG and could be the key to functionality not realizable in metallic or half-metallic oxide-based devices.