Manipulating the Magnetic Characteristics of Defective SrTiO3 (001) Surfaces Through O2 Adsorption: An Investigation via Hybrid Functional Calculations

Abstract

The electronic and magnetic properties of defective SrTiO₃ (001) surfaces were examined through hybrid functional calculations, focusing on the impact of O₂ adsorption. Among the various vacancy types considered—oxygen vacancy (V_O), titanium vacancy (V_Ti), strontium vacancy (V_Sr), V_Ti + V_O complex (V_Ti-O), and V_Sr + V_O complex (V_Sr-O)—only V_O, V_Ti, and V_Ti-O exhibit magnetic moments. At low O₂ coverage, the adsorption of a single O₂ molecule onto each defective surface results in a reduction of the magnetic moments for surfaces with V_O, V_Ti, or V_Ti-O, potentially decreasing to zero. In contrast, the magnetic moment of surfaces with V_Sr-O increases from zero to 2 μ_B. Upon the addition of a second O₂ molecule at high O₂ coverage, the magnetic moments of surfaces with V_O and V_Ti are significantly enhanced, attributed to the polarization of the p electrons of the two adsorbed O₂ molecules. Surfaces with V_Ti-O or V_Sr-O complex defects do not adsorb additional O₂ molecules, and surfaces with V_Sr are unable to adsorb O₂ molecules. The variation in magnetic moments for the defective surfaces is correlated with the number of electrons acquired by the adsorbed O₂ molecules.