Research Update: Plentiful magnetic moments in oxygen deficient SrTiO3

Abstract

Correlated band theory is employed to investigate the magnetic and electronic properties of different arrangements of oxygen di-and tri-vacancy clusters in SrTiO3. Hole and electron doping of oxygen deficient SrTiO3 yields various degrees of magnetization as a result of the interaction between localized magnetic moments at the defected sites. Different kinds of Ti atomic orbital hybridization are described as a function of the doping level and defect geometry. We find that magnetism in SrTiO 3−δ is sensitive to the arrangement of neighbouring vacancy sites, charge carrier density, and vacancy-vacancy interaction. Permanent magnetic moments in the absence of vacancy doping electrons are observed. Our description of the charged clusters of oxygen vacancies widens the previous descriptions of mono and multi-vacancies and points out the importance of the controled formation at the atomic level of defects for the realization of transition metal oxide based devices with a desirable magnetic performance.

Emerging Diluted Ferromagnetism in High‐Tc Superconductors Driven by Point Defect Clusters

“…In addition, many superconducting materials have an anisotropic structure similar to YBCO and could therefore have similar complex point defects, opening up the possibility to search for the presence of magnetism in the vicinity of superconductivity in all those candidate materials. Our results may also be generalized to other defective perovskite‐based systems in which correlation effects between defect sites might bring new functionalities, as shown by a recent theoretical work on oxygen‐deficient SrTiO 3 , which predicts that different configuration of clustered oxygen vacancies may yield various degrees of magnetization as a result of the interaction between localized magnetic moments at the defect sites …”

“…Our results may also be generalized to other defective perovskite-based systems in which correlation effects between defect sites might bring new functionalities, as shown by a recent theoretical work on oxygen-defi cient SrTiO 3 , which predicts that different confi guration of clustered oxygen vacancies may yield various degrees of magnetization as a result of the interaction between localized magnetic moments at the defect sites. [ 35 ]…”

Interconversion of intrinsic defects in SrTiO3(001)

“…The lattice parameter was preoptimized for each value of U eff we considered (0 -8 eV), yielding a corresponding range of a 0 (3.89 -3.95 Å) and a 0 remained fixed while internal degrees of freedom were fully relaxed in all subsequent calculations. Most calculations were performed using U = 4 eV [34] and a supercell parameter of 15.69 Å, corresponding to the STO lattice parameter a 0 = 3.92 Å (less than 0.4% different from the experimental value of 3.905 Å). We found this approach to provide a reasonable compromise between PBEsol proper, which gives more accurate lattice parameters, and PBEsol + U (with U = 8 eV), which yields a more acccurate value of the band gap, but overestimates the lattice parameters by ~1.2%.…”

Interface Engineering and Emergent Phenomena in Oxide Heterostructures

“…This explains why the ferromagnetic behaviors are observed in the relatively insulating samples . The local magnetic moment may be arising from oxygen with unpaired electrons and/or localized states from Ti . The second category is labeled as “meta‐magnetic” phase, characterized by the anisotropic magnetoresistance (AMR) and anomalous Hall effect .…”