Insights into the structural, electronic, and magnetic properties of Fe2−x Ti x O3/Fe2O3 thin films with x = 0.44 grown on Al2O3 (0001)

Dennenwaldt, Teresa; Lübbe, M.; Winklhofer, Michael; Müller, Alexander; Döblinger, Markus; Nabi, Hasan Sadat; Gandman, M. G.; Cohen-Hyams, T.; Kaplan, Wayne D.; Moritz, Wolfgang; Scheu, Christina

doi:10.1007/s10853-014-8572-x

Cited by 5 publications

(4 citation statements)

References 59 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…In fact, the intensity ratio of the Fe L 3 /L 2 peaks can be used as an indicator of the Fe oxidation state. High ratios (5–7) indicate Fe in higher oxidation states (+II–+IV); low ratios (4 and below) reduced/metallic Fe. , The Fe L 3 /L 2 peak ratio along the profile is therefore highlighted in the right side of panel B. Oxidized iron is thus only found at the particle edges (and within the perovskite bulk), metallic iron in the rod center. Note that this can be also indirectly derived from the internal HAADF contrast of the iron rod: as the HAADF intensity is mostly dominated by the average atom number, oxygen-rich areas are darker than iron-rich ones, and in turn, the oxygen concentration is highest along the rod edge.…”

Section: Resultsmentioning

confidence: 99%

Exsolution of Fe and SrO Nanorods and Nanoparticles from Lanthanum Strontium Ferrite La_0.6Sr_0.4FeO_3−δ Materials by Hydrogen Reduction

et al. 2015

View full text Add to dashboard Cite

Formation of uniform Fe and SrO rods as well as nanoparticles following controlled reduction of La0.6Sr0.4FeO3−δ (LSF) and Ni-LSF samples in dry and moist hydrogen is studied by aberration-corrected electron microscopy. Metallic Fe and SrO precipitate from the perovskite lattice as rods of several tenths of nm and thicknesses up to 20 nm. Based on a model of Fe whisker growth following reduction of pure iron oxides, Fe rod exsolution from LSF proceeds via rate-limiting lattice oxygen removal. This favors the formation of single iron metal nuclei at the perovskite surface, subsequently growing as isolated rods. The latter is only possible upon efficient removal of reduction-induced water and, subsequently, reduction of Fe +III/+IV to Fe(0). If water remains in the system, no reduction or rod formation occurs. In contrast, formation of SrO rods following reduction in dry hydrogen is a catalytic process aided by Ni particles. It bears significant resemblance to surface diffusion-controlled carbon whisker growth on Ni, leading to similar extrusion rods and filaments. In addition to SrO rod growth, the exsolution of Fe nanoparticles and, subsequently, Ni–Fe alloy particles is observed. The latter have also been observed under static hydrogen reduction. Under strict control of the experimental parameters, the presented data therefore open an attractive chemically driven pathway to metal nanoarchitectures beyond the formation of “simple” nanoparticles.

show abstract

Section: Resultsmentioning

confidence: 99%

Exsolution of Fe and SrO Nanorods and Nanoparticles from Lanthanum Strontium Ferrite La_0.6Sr_0.4FeO_3−δ Materials by Hydrogen Reduction

et al. 2015

View full text Add to dashboard Cite

show abstract

“…The growth of corundum thin films on α-Al 2 O 3 (0001) has been reported in several experimental studies exploiting different techniques such as molecular beam epitaxy [49,50,51], pulsed laser deposition [52], helicon plasma- [53] or r.f. magnetron sputtering [54].…”

Section: Discussionmentioning

confidence: 99%

Interaction-driven spin-orbit effects and Chern insulating phases in corundum-based 4d and 5d oxide honeycomb lattices

Köksal

2019

Journal of Physics and Chemistry of Solids

Self Cite

View full text Add to dashboard Cite

Using density functional theory calculations with a Hubbard U , we explore topologically nontrivial phases in X 2 O 3 honeycomb layers with X = 4d and 5d cation inserted in the band insulator α-Al 2 O 3 along the [0001]direction. Several promising candidates for quantum anomalous Hall insulators (QAHI) are identified. In particular, for X = Tc and Pt spin-orbit coupling (SOC) opens a gap of 54 and 59 meV, respectively, leading to Chern insulators (CI) with C = -2 and -1. The nature of different Chern numbers is related to the corresponding spin textures. The Chern insulating phase is sensitive to the Coulomb repulsion strength: X = Tc undergoes a transition from a CI to a trivial metallic state beyond a critical strength of U c = 2.5 eV. A comparison between the isoelectronic metastable FM phases of X = Pd and Pt emphasizes the intricate balance between electronic correlations and SOC: while the former is a trivial insulator, the latter is a Chern insulator. In addition, X = Os turns out to be a FM Mott insulator with an unpaired electron in the t 2g manifold where SOC induces an unusually high orbital moment of 0.34 µ B along the z-axis. Parallels to the 3d honeycomb corundum cases are discussed.

show abstract

“…only X and Al ions, instead of three or four different cations in a perovskite superlattice). Several studies have reported the successful growth of corundum thin films on α-Al 2 O 3 (0001) using molecular beam epitaxy [53][54][55] , pulsed laser deposition 56 , helicon plasma-57 or r.f. magnetron sputtering 58 .…”

Section: Discussionmentioning

confidence: 99%

Confinement-driven electronic and topological phases in corundum-derived 3d -oxide honeycomb lattices

Köksal

Baidya

2018

Phys. Rev. B

Self Cite

View full text Add to dashboard Cite

Using density functional theory calculations including an on-site Coulomb term, we explore electronic and possibly topologically nontrivial phases in 3d transition metal oxide honeycomb layers confined in the corundum structure (α-Al2O3) along the [0001] direction. In most cases the ground state is a trivial antiferromagnetic Mott insulator, often with distinct orbital or spin states compared to the bulk phases. With imposed symmetry of the two sublattices the ferromagnetic phases of Ti, Mn, Co and Ni exhibit a characteristic set of four bands, two relatively flat and two with a Dirac crossing at K, associated with the single electron occupation of e g (Ti) or eg (Mn, Co, Ni) orbitals. Our results indicate that the Dirac point can be tuned to the Fermi level using strain. Applying spin-orbit coupling (SOC) leads to a substantial anomalous Hall conductivity with values up to 0.94 e 2 /h. Moreover, at a Al 2 O 3 = 4.81Å we identify a particularly strong effect of SOC with out-of-plane easy axis for (T i2O3)1/(Al2O3)5(0001) which stabilizes dynamically the system. Due to the unusually high orbital moment of -0.88µB that nearly compensates the spin moment of 1.01 µB, this system emerges as a candidate for the realization of the topological Haldane model of spinless fermions. Parallels to the perovskite analogs (LaXO3)2/(LaAlO3)4(111) are discussed.

show abstract

Insights into the structural, electronic, and magnetic properties of Fe2−x Ti x O3/Fe2O3 thin films with x = 0.44 grown on Al2O3 (0001)

Abstract: The interface between hematite (a-Fe 2 III

Cited by 5 publications

References 59 publications

Exsolution of Fe and SrO Nanorods and Nanoparticles from Lanthanum Strontium Ferrite La_0.6Sr_0.4FeO_3−δ Materials by Hydrogen Reduction

Exsolution of Fe and SrO Nanorods and Nanoparticles from Lanthanum Strontium Ferrite La_0.6Sr_0.4FeO_3−δ Materials by Hydrogen Reduction

Interaction-driven spin-orbit effects and Chern insulating phases in corundum-based 4d and 5d oxide honeycomb lattices

Confinement-driven electronic and topological phases in corundum-derived 3d -oxide honeycomb lattices

Contact Info

Product

Resources

About

Insights into the structural, electronic, and magnetic properties of Fe2−x Ti x O3/Fe2O3 thin films with x = 0.44 grown on Al2O3 (0001)

Abstract: The interface between hematite (a-Fe 2 III

Cited by 5 publications

References 59 publications

Exsolution of Fe and SrO Nanorods and Nanoparticles from Lanthanum Strontium Ferrite La0.6Sr0.4FeO3−δ Materials by Hydrogen Reduction

Exsolution of Fe and SrO Nanorods and Nanoparticles from Lanthanum Strontium Ferrite La0.6Sr0.4FeO3−δ Materials by Hydrogen Reduction

Interaction-driven spin-orbit effects and Chern insulating phases in corundum-based 4d and 5d oxide honeycomb lattices

Confinement-driven electronic and topological phases in corundum-derived 3d -oxide honeycomb lattices

Contact Info

Product

Resources

About

Exsolution of Fe and SrO Nanorods and Nanoparticles from Lanthanum Strontium Ferrite La_0.6Sr_0.4FeO_3−δ Materials by Hydrogen Reduction

Exsolution of Fe and SrO Nanorods and Nanoparticles from Lanthanum Strontium Ferrite La_0.6Sr_0.4FeO_3−δ Materials by Hydrogen Reduction