Effect of LaAlO$_{3}$ Stoichiometry on Magneto- Transport Properties of LaAlO$_{3}$/SrTiO$_{3}$ heterostructure*

The formation of 2DEG in the interface of two insulators, LaAlO$_{3}$ (LAO) and SrTiO$_{3}$ (STO), has stimulated intense research on its origin and applications. We present our low temperature magneto-transport studies on series of high quality LaAlO$_{3}$/SrTiO$_{3}$ hetero-structure samples with different growth and treatment conditions. Parameters that affect interface properties, such as substrate orientation, deposition oxygen partial pressure and the related oxygen vacancies, LaAlO$_{3}$ layer thickness, and LaAlO$_{3}$~stoichiometry, are controlled through processing modifications and post-processing treatments. By looking at the feature of anisotropic magnetoresistance in different samples, the critical effect of LaAlO$_{3}$ stoichiometry is identified, indicating possible candidates that give raise to the magnetism. The authors thank Air Force Office of Scientific Research (grant {\#}FA9550-12-1-0441) for funding support.