Electronic structure of oxygen vacancies in<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:msub><mml:mrow><mml:mi mathvariant="normal">SrTiO</mml:mi></mml:mrow><mml:mn>3</mml:mn></mml:msub></mml:math>and<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:msub><mml:mrow><mml:mi mathvariant="normal">LaAlO</mml:mi></mml:mrow><mml:mn>3</mml:mn></mml:msub></mml:math>

Mitra, Chandrima; Lin, Chungwei; Robertson, John; Demkov, Alexander A.

doi:10.1103/physrevb.86.155105

Cited by 163 publications

(140 citation statements)

References 49 publications

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“…The neighboring Ti atom, labeled A in the figure, moves away from the vacancy site by 0.07 Å relative to its ideal position in an unrelaxed supercell. This is in contrast to what is observed in Ti-OV-Ti, in the absence of Co, where the two Ti atoms are actually found to move closer to the vacancy site [38]. We do not find any displacement of Co from its ideal position.…”

Section: Vcontrasting

confidence: 56%

“…A plausible source of extrinsic carriers is oxygen vacancies (OV), which are commonly occurring defects in oxides, especially thin films. Creation of an OV in STO results in two additional electrons that can potentially convert Co from a +4 to a +2 valence state [37,38,39]. Hence understanding the role of oxygen vacancies in the observed magnetism in this system (which henceforth would be denoted as SrTi 1-x Co x O 3-δ ) is crucial.…”

Section: IVmentioning

confidence: 99%

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Role of oxygen vacancies in room-temperature ferromagnetism in cobalt-substitutedSrTiO3

et al. 2014

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Ferromagnetic insulating behaviour has recently been demonstrated in cobalt-substituted SrTiO 3 at room temperature [1]. Experimentally, it was found that a well-defined hysteresis loop only occurs at high Co concentrations of 30-40%. X-ray photoelectron spectroscopy also indicated that Co substitutes for Ti with Co being in high-spin +2 oxidation state. In this work, we employ density-functional theory to explain the experimentally observed properties of cobalt-substituted SrTiO 3 . We examine in detail the role of oxygen vacancy (OV) defects and their formation of defect complexes with the Co ions as the origin of the ferromagnetic insulating behaviour. Our first-principles thermodynamic calculations indicate that OV defects are much more likely to occur next to Co atoms where their formation energies could be reduced by as much as 1.28 eV compared to that in bulk SrTiO 3 . We also find that Co in these Co-OV complexes occurs in the high-spin state in agreement with core level spectroscopy, and identify a linear arrangement of the Co-OV defect complexes to be the most energetically favourable structure. These defect complexes are also shown to interact ferromagnetically and that their magnetic interaction is found to be short-ranged, consistent with the relatively high Co concentrations needed experimentally for ferromagnetism to be observed in cobalt-substituted SrTiO 3 . I.Introduction The discovery of room-temperature ferromagnetism in doped transition metal oxides by Matsumoto et al. [2] has initiated many theoretical and experimental studies, owing to potential applications of these materials in spintronics. For example, , SnO 2 [5-6], In 2 O 3 [7][8] and TiO 2 [9][10], have all been reported to show room-temperature ferromagnetism when doped with magnetic ions. Increasing the Curie temperature and being able to control the spin degrees of freedom remain major challenges in this field. In this respect, defects in these materials, both intrinsic and extrinsic, play an important role. Defects provide additional carriers to the system (electrons or holes) which could significantly alter magnetic interactions and the Curie temperature in these materials.

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Section: Vcontrasting

confidence: 56%

Section: IVmentioning

confidence: 99%

Role of oxygen vacancies in room-temperature ferromagnetism in cobalt-substitutedSrTiO3

et al. 2014

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“…However, oxide interfaces also bring along many challenges. Ionic defects such as oxygen vacancies might play an important role in determining the electronic structure [8][9][10][11][12][13]. Understanding and controlling these material-physics issues-and the effect they have on the properties-is essential to fully explore the new functionalities that these fascinating compounds might bring along [14].…”

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Competition between Covalent Bonding and Charge Transfer at Complex-Oxide Interfaces

et al. 2014

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Here we study the electronic properties of cuprate-manganite interfaces. By means of atomic resolution electron microscopy and spectroscopy, we produce a subnanometer scale map of the transition metal oxidation state profile across the interface between the high Tc superconductor YBa 2 Cu 3 O 7−δ and the colossal magnetoresistance compound (La,Ca)MnO 3 . A net transfer of electrons from manganite to cuprate with a peculiar nonmonotonic charge profile is observed. Model calculations rationalize the profile in terms of the competition between standard charge transfer tendencies (due to band mismatch), strong chemical bonding effects across the interface, and Cu substitution into the Mn lattice, with different characteristic length scales. DOI: 10.1103/PhysRevLett.112.196802 PACS numbers: 73.20.-r, 74.20.-z, 74.78.Fk A detailed understanding of the charge transfer that occurs across semiconductor interfaces has led to the development of two-dimensional electron gases [1], as well as the integer and fractional quantum Hall effect [2][3][4]. Interfaces between transition-metal oxides (TMOs) have the potential for even richer physics, due to the presence of several competing interactions with similar characteristic energies. The competition between electrostatic effects-similar to those at work in semiconductor heterostructures-and orbital physics characteristic of TMOs can give rise to exotic electronic reconstructions and novel physical behaviors. In heterostructures of LaAlO 3 =SrTiO 3 , the observation of a metalinsulator transition at the interface of these nonmagnetic (bulk) insulators [5] along with superconductivity [6] and magnetism [7]) sparked considerable interest. However, oxide interfaces also bring along many challenges. Ionic defects such as oxygen vacancies might play an important role in determining the electronic structure [8][9][10][11][12][13]. Understanding and controlling these material-physics issues-and the effect they have on the properties-is essential to fully explore the new functionalities that these fascinating compounds might bring along [14].Ferromagnetic-superconducting interfaces of La 2=3 Ca 1=3 MnO 3 =YBa 2 Cu 3 O 7−δ (LCMO/YBCO) have attracted much attention. This system is a paradigmatic example of competition between strongly correlated systems with different ground states. It has been proposed, based on the difference between chemical potentials, that electronic charge would be transferred from the manganite to the cuprate [15,16]. This mechanism, however, does not consider the details of the interface. The interfacial electronic structure depends on other details, such as the atomic termination [17] for each material. At the LCMO/YBCO interface both a change in the orbital occupation and a net magnetic moment are induced in the cuprate [18,19]. Model calculations [20] were able to explain different experimental results regarding the competition between ferromagnetism and superconductivity [21]. However, the effect of charge transfer was not studied. Very recently, cross-se...

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“…Compared to the neutral vacancy formation energy in undoped STO, which is about 6.5eV [51], the presence of a Co atom substantially (~2 eV) lowers the formation energy, because Co provides empty low energy states for the two extra electrons associated with the vacancy to occupy. From this point on, we assume that the vacancy is adjacent to substitutional Co.…”

Section: F Role Of Oxygen Vacanciesmentioning

confidence: 99%

Oxygen vacancy-mediated room-temperature ferromagnetism in insulating cobalt-substituted SrTiO3epitaxially integrated with silicon

et al. 2013

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Electronic structure of oxygen vacancies inSrTiO3andLaAlO3

Abstract: The electronic structure of oxygen vacancies in bulk perovskite oxides SrTiO 3 and LaAlO 3 is studied using the Heyd, Scuseria, Ernzerhof (HSE) hybrid density functional. In SrTiO 3 the oxygen vacancy defect introduces a localized state comprised of

Cited by 163 publications

References 49 publications

Role of oxygen vacancies in room-temperature ferromagnetism in cobalt-substitutedSrTiO3

Role of oxygen vacancies in room-temperature ferromagnetism in cobalt-substitutedSrTiO3

Competition between Covalent Bonding and Charge Transfer at Complex-Oxide Interfaces

Oxygen vacancy-mediated room-temperature ferromagnetism in insulating cobalt-substituted SrTiO3epitaxially integrated with silicon

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