Considerable spin asymmetry of deep valence states induced by partial neutralization of charged SrTiO3(011) surfaces

Abstract

Recently, spin asymmetry in O 2p related deep valence states was evidenced in SrTiO3(001) [Popescu et al., Phys. Scr. 99(10), 105925 (2024)]. In this work, we report the detection of a much higher (about four times) spin asymmetry in SrTiO3(011) by spin resolved photoelectron spectroscopy, with samples characterized also by core level x-ray photoelectron spectroscopy and low energy electron diffraction. The explanation of a so important spin asymmetry is related to the partial neutralization of O2(4−) or SrTiO(4+) end layers. Missing electrons from O 2p states in the case of O2 terminations enable robust atomic spins, according to Hund’s rule. The parallel analysis of core level shifts for surface atoms and the amplitude of spin asymmetry suggests that 50% of the oxygens from the surface SrO layer of SrTiO3(001) have a 2p5 configuration with an unpaired electron (the rest are in a 2p6 configuration), while in the case of O2 terminated SrTiO3(011), about 50% of surface oxygens have a 2p5 configuration and 50% of surface oxygens are neutral (2p4), yielding a net charge per O2 surface unit cell of (−1) instead of (−4). The magnetization is oriented along the rows formed by the (4 × 1) reconstruction in the 01̄1 in-plane direction.