Valence-state reflectometry of complex oxide heterointerfaces

Hamann-Borrero, J. E.; Macke, S.; Choi, Woo Seok; Sutarto, Ronny; He, Feizhou; Radi, Abdullah; Elfimov, Ilya; Green, Robert J.; Haverkort, M. W.; Zabolotnyy, V. B.; Lee, Ho Nyung; Sawatzky, G. A.; Hinkov, V.

doi:10.1038/npjquantmats.2016.13

Cited by 26 publications

(22 citation statements)

References 53 publications

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“…The LCO films were subsequently capped with an ultrathin STO layer with a thickness of 5 u.c. to prevent the formation of nonstoichiometric surface due to oxygen vacancies ( 17 , 20 ). Results from x-ray diffraction (XRD) measurements confirm excellent epitaxial growth of all layers.…”

Section: Resultsmentioning

confidence: 99%

Nanoscale ferroelastic twins formed in strained LaCoO ₃ films

et al. 2019

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The coexistence and coupling of ferroelasticity and magnetic ordering in a single material offers a great opportunity to realize novel devices with multiple tuning knobs. Complex oxides are a particularly promising class of materials to find multiferroic interactions due to their rich phase diagrams, and are sensitive to external perturbations. Still, there are very few examples of these systems. Here, we report the observation of twin domains in ferroelastic LaCoO3 epitaxial films and their geometric control of structural symmetry intimately linked to the material’s electronic and magnetic states. A unidirectional structural modulation is achieved by selective choice of substrates having twofold rotational symmetry. This modulation perturbs the crystal field–splitting energy, leading to unexpected in-plane anisotropy of orbital configuration and magnetization. These findings demonstrate the use of structural modulation to control multiferroic interactions and may enable a great potential for stimulation of exotic phenomena through artificial domain engineering.

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Section: Resultsmentioning

confidence: 99%

Nanoscale ferroelastic twins formed in strained LaCoO ₃ films

et al. 2019

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“…The optical constants of the materials under study were constructed as described in refs 24,25,30 . First the measured XAS spectra are normalized to tabulated scattering factors 39 .…”

Section: Methodsmentioning

confidence: 99%

“…In this regard only few works have succeeded to extract information about orbital occupancies and reconstruction profiles from RXR 27–29 , showing RXR to be sensitive enough to resolve fine orbital changes of the order of ~3–5%. Recently, valence state profiles have also been determined 30 .…”

Section: Introductionmentioning

confidence: 99%

Site-selective spectroscopy with depth resolution using resonant x-ray reflectometry

Hamann-Borrero

Macke

Gray

et al. 2017

Sci Rep

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Combining dissimilar transition metal oxides (TMOs) into artificial heterostructures enables to create electronic interface systems with new electronic properties that do not exist in bulk. A detailed understanding of how such interfaces can be used to tailor physical properties requires characterization techniques capable to yield interface sensitive spectroscopic information with monolayer resolution. In this regard resonant x-ray reflectivity (RXR) provides a unique experimental tool to achieve exactly this. It yields the element specific electronic depth profiles in a non-destructive manner. Here, using a YBa2Cu3O7−δ (YBCO) thin film, we demonstrate that RXR is further capable to deliver site selectivity. By applying a new analysis scheme to RXR, which takes the atomic structure of the material into account, together with information of the local charge anisotropy of the resonant ions, we obtained spectroscopic information from the different Cu sites (e.g., chain and plane) throughout the film profile. While most of the film behaves bulk-like, we observe that the Cu-chains at the surface show characteristics of electron doping, whereas the Cu-planes closest to the surface exhibit an orbital reconstruction similar to that observed at La1−xCaxMnO3/YBCO interfaces.

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“…Remarkably, another fingerprint of these multivalent states is the prepeak centered at ≈777.4 eV, which is the characteristic for the Co 2+ ions. [ 36,38 ] Previously, Co 2+ ions are expected to generate due to the introduction of oxygen deficiency. [ 20,39 ] Note that our LCO films were grown under an oxygen rich atmosphere, oxygen vacancies should reduce to the minimum.…”

Section: Figurementioning

confidence: 99%

Charge‐Transfer‐Induced Multivalent States with Resultant Emergent Magnetism in Transition‐Metal Oxide Heterostructures

Niu

Fang

Zhang

et al. 2020

Adv Elect Materials

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Transition‐metal oxide (TMO) heterostructures provide fertile grounds for creating and manipulating intriguing properties and functionalities. At the interface of TMO heterostructures, electronic reconstructions generally occur via charge transfer and lead to an extraordinary spectrum of emergent phenomena but unattainable in their bulk constituents. However, the basic mechanism of charge transfer at the interface is not fully determined or even understood in heterostructures, which may hide the underlying mechanisms and intriguing physics. Herein, an intrinsic charge transfer and resultant exotic ferromagnetism are unambiguously observed in the heterostructures between the nonmagnetic LaCoO3 (LCO) and SrTiO3 (STO). Combining element‐specific X‐ray absorption spectroscopy and atomic multiplet fitting, direct evidence of charge transfer‐induced multivalence of cobalt ions, interactions of which would contribute to the novel magnetism beyond the intuition, in concert with first‐principles density‐functional‐theory calculations, is demonstrated. Beyond LCO/STO system, a more broadly applicable principle for the heterostructures between 3d TMO and STO where charge transfer and resultant multivalence or conducting interfaces are coexistent is establish. This study represents an advance that the electronic reconstruction and the multiple electron configurations of 3d transition metal ions will constitute a powerful tool for the designs of functional materials and creations of unconventional physical properties.

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Valence-state reflectometry of complex oxide heterointerfaces

Cited by 26 publications

References 53 publications

Nanoscale ferroelastic twins formed in strained LaCoO ₃ films

Nanoscale ferroelastic twins formed in strained LaCoO ₃ films

Site-selective spectroscopy with depth resolution using resonant x-ray reflectometry

Charge‐Transfer‐Induced Multivalent States with Resultant Emergent Magnetism in Transition‐Metal Oxide Heterostructures

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Valence-state reflectometry of complex oxide heterointerfaces

Cited by 26 publications

References 53 publications

Nanoscale ferroelastic twins formed in strained LaCoO 3 films

Nanoscale ferroelastic twins formed in strained LaCoO 3 films

Site-selective spectroscopy with depth resolution using resonant x-ray reflectometry

Charge‐Transfer‐Induced Multivalent States with Resultant Emergent Magnetism in Transition‐Metal Oxide Heterostructures

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Nanoscale ferroelastic twins formed in strained LaCoO ₃ films

Nanoscale ferroelastic twins formed in strained LaCoO ₃ films