  Understanding, creating, and manipulating spin polarization of
two-dimensional electron gases at complex oxide interfaces presents an
experimental challenge. For example, despite almost a decade long research
effort, the microscopic origin of ferromagnetism in LaAlO3/SrTiO3
heterojunction is still an open question. Here, by using a prototypical
two-dimensional electron gas (2DEG) which emerges at the interface between band
insulator SrTiO3 and antiferromagnetic Mott insulator LaTiO3 , the experiment
reveals the evidence for magnetic phase separation in hole-doped Ti d1 t2g
system resulting in spin-polarized 2DEG. The details of electronic and magnetic
properties of the 2DEG were investigated by temperature-dependent d.c.
transport, angle-dependent X-ray photoemission spectroscopy, and
temperature-dependent magnetoresistance. The observation of clear hysteresis in
magnetotransport at low magnetic fields implies spin-polarization from magnetic
islands in the hole rich LaTiO3 near the interface. These findings emphasize
the role of magnetic instabilities in doped Mott insulators thus providing
another path for designing all-oxide structures relevant to spintronics
applications.
