Thickness Dependence of Magnetic Behavior of LaAlO3/SrTiO3 Heterostructures

Thickness dependence of magnetic properties of LaAlO3 (LAO)/SrTiO3 (STO) heterostructures is systematically studied. It is found that the magnetic moment is rather robust at elevated temperatures in the samples grown under ultralow P-O2 of 1 x 10(-8) Torr, indicating room-temperature ferromagnetism in the LaAlO3/SrTiO3 heterostructures. Spin-glass-like behavior is observed in the LAO/STO heterostructures with the LAO thickness ranging from 5 to 90 unit cells (2-35.2 nm). As the LAO layer becomes thicker, the blocking temperature of spin-glass-like behavior decreases and magnetic moment weakens, which may be related to the reduced density of oxygen vacancies at the interfacial TiO2 layer. It is believed that the well-controlled magnetism by tuning the LAO thickness may open an avenue for the potential application of spintronics with LaAlO3/SrTiO3 heterostructures.