Tunable Magnetic and Half-metallic Properties of the Two-dimensional Electron Gas in LaAlO3/SrTiO3 (111) Heterostructures

ABSTRACT: Half-metallic materials have gained a lot of attention because of their unique properties and their application in spintronic devices. Despite the fact that these materials have studied by several research groups there are very limited studies on heterostructure (HS) systems. In the current study we have investigated the electronic and magnetic properties of (LaAlO3)6.5/(SrTiO3)2.5 (111) HS using density functional theory (DFT) calculations. We demonstrate that the system exhibits a 100% spin-polarized two-dimensional electron gas (2DEG) which is extremely confined to the Ti 3d orbitals of the SrTiO3 layers. In particular, this system can keep its half-metallic properties under different in-plane strains from -3 to 2%. This property proves that this material has relatively stable half-metallic properties. In addition, the conducting and magnetic ground states of system also can be tailored by changing in-plane strain and interfacial cation intermixing of La and Sr (Sr/La intermixing). By increasing the in-plane lattice parameters, this system has the ability to be evolved from a nonmagnetic to ferromagnetic metal and then to half-metal and by further increasing the in-plane lattice parameter it becomes a ferromagnetic insulator. Sr/La intermixing can destroy the original half-metallic properties and the system exhibits an AFM Mott-type insulator phase. Our results demonstrate that the system has high potential for application in the field of spintronics, and open prospect of using LaAlO3/SrTiO3 (111) HSs to explore quantum phase transitions.