Anomalously deep polarization in 
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 (001) interfaced with an epitaxial ultrathin manganite film

Wang, Zhen; Tao, Jing; Yu, Liping; Guo, Hangwen; Chen, Lina; Han, Myung‐Geun; Xin, Huolin L.; Kisslinger, Kim; Plummer, E. W.; Zhang, Jiandi; Zhu, Yimei

doi:10.1103/physrevb.94.155307

Cited by 18 publications

(15 citation statements)

References 53 publications

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“…1 A and B, respectively. The data show that, in this metallic thin film, there are no ferroelectric-like displacements in either of the two materials, as opposed to ultrathin insulating LSMO where strong ferroelectric-like displacements have been observed (34). The ABF−STEM image displays a zig-zag arrangement of Mn−O−Mn and Ti−O−Ti chains, due to tilts of the octahedra.…”

Section: Atomic-scale Structural Data and Formal Oxidation Statesmentioning

confidence: 77%

Atomic-scale determination of spontaneous magnetic reversal in oxide heterostructures

Saghayezhian

Kouser

Wang

et al. 2019

Proc. Natl. Acad. Sci. U.S.A.

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Interfaces between transition metal oxides are known to exhibit emerging electronic and magnetic properties. Here we report intriguing magnetic phenomena for La 2/3 Sr 1/3 MnO 3 films on an SrTiO 3 (001) substrate (LSMO/STO), where the interface governs the macroscopic properties of the entire monolithic thin film. The interface is characterized on the atomic level utilizing scanning transmission electron microscopy and electron energy loss spectroscopy (STEM-EELS), and density functional theory (DFT) is employed to elucidate the physics. STEM-EELS reveals mixed interfacial stoichiometry, subtle lattice distortions, and oxidation-state changes. Magnetic measurements combined with DFT calculations demonstrate that a unique form of antiferromagnetic exchange coupling appears at the interface, generating a novel exchange spring-type interaction that results in a remarkable spontaneous magnetic reversal of the entire ferromagnetic film, and an inverted magnetic hysteresis, persisting above room temperature. Formal oxidation states derived from electron spectroscopy data expose the fact that interfacial oxidation states are not consistent with nominal charge counting. The present work demonstrates the necessity of atomically resolved electron microscopy and spectroscopy for interface studies. Theory demonstrates that interfacial nonstoichiometry is an essential ingredient, responsible for the observed physical properties. The DFT-calculated electrostatic potential is flat in both the LSMO and STO sides (no internal electric field) for both Sr-rich and stoichiometric interfaces, while the DFT-calculated charge density reveals no charge transfer/ accumulation at the interface, indicating that oxidation-state changes do not necessarily reflect charge transfer and that the concept of polar mismatch is not applicable in metal−insulator polar−nonpolar interfaces. magnetism | thin films | electron microscopy | oxide interfaces | density functional theory T ransition metal oxides (TMOs) exhibit a wide range of electrical, magnetic, and optical properties largely because they can be easily alloyed and the 10 slots in the transition metal atom d orbitals allow for very diverse spin arrangements. Adding strong electron−lattice coupling and easily formed oxygen vacancies to this mix, the result is a large number of coupled degrees of freedom. Therefore, it is not surprising that TMO heterostructures exhibit highly unusual behavior, induced by interfaces between different oxides where symmetry discontinuities occur, leading to properties that are absent in bulk (1-5). A wellknown example is the LaAlO 3 /SrTiO 3 (001) heterostructure, where a 2D electron gas with high mobility forms at the interface between two insulating oxides (6), including the appearance of superconductivity (7) and background ferromagnetic (FM) ordering (8). In many cases, the symmetry discontinuity at the interface strongly modifies the transition metal−oxygen octahedra network, inducing changes in local structure (bond geometry) and local stoichiometry. Thes...

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Section: Atomic-scale Structural Data and Formal Oxidation Statesmentioning

confidence: 77%

Atomic-scale determination of spontaneous magnetic reversal in oxide heterostructures

Saghayezhian

Kouser

Wang

et al. 2019

Proc. Natl. Acad. Sci. U.S.A.

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“…Models proposed to explain the thickness-dependent transitions, including the interfacial/surface segregation of oxygen vacancies, interfacial chemical interdiffusion, charge transfer and unique strain driven interfacial orbital reconstructions. [8,[13][14][15][16][17] Like many complex oxide materials with the ABO3 perovskite crystal structure, LSMO films exhibit a polar stacking along the [001] growth direction and a polar discontinuity will exist at interfaces with non-polar substrates. [13,18,19] In similar polar systems , e.g.…”

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confidence: 99%

Structural distortions at polar manganite interfaces

et al. 2017

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Electronic, lattice, and spin interactions at the interfaces between crystalline complex transition metal oxides can give rise to a wide range of functional electronic and magnetic phenomena not found in bulk. At hetero-interfaces, these interactions may be enhanced by combining oxides where the polarity changes at the interface. The physical structure between non-polar SrTiO3 and polar La1-xSrxMnO3(x=0.2) is investigated using high resolution synchrotron x-ray diffraction to directly determine the role of structure in compensating the polar discontinuity. At both the oxideoxide interface and vacuum-oxide interfaces, the lattice is found to expand and rumple along the growth direction. The SrTiO3/La1-xSrxMnO3 interface also exhibits intermixing of La and Sr over a few unit cells.

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“…Cross-sectional TEM samples are prepared by focused ion beam with Ga + ions followed with gentle Ar + ion milling 38 . STEM/EELS experiments are performed on a double aberration-corrected microscope JEOL-ARM200F operating at 200 keV, with a dual energy-loss spectrometer and a cold-emission electron source.…”

Section: Methodsmentioning

confidence: 99%

Artificial two-dimensional polar metal at room temperature

et al. 2018

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Polar metals, commonly defined by the coexistence of polar crystal structure and metallicity, are thought to be scarce because the long-range electrostatic fields favoring the polar structure are expected to be fully screened by the conduction electrons of a metal. Moreover, reducing from three to two dimensions, it remains an open question whether a polar metal can exist. Here we report on the realization of a room temperature two-dimensional polar metal of the B-site type in tri-color (tri-layer) superlattices BaTiO3/SrTiO3/LaTiO3. A combination of atomic resolution scanning transmission electron microscopy with electron energy-loss spectroscopy, optical second harmonic generation, electrical transport, and first-principles calculations have revealed the microscopic mechanisms of periodic electric polarization, charge distribution, and orbital symmetry. Our results provide a route to creating all-oxide artificial non-centrosymmetric quasi-two-dimensional metals with exotic quantum states including coexisting ferroelectric, ferromagnetic, and superconducting phases.

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Anomalously deep polarization in SrTiO3 (001) interfaced with an epitaxial ultrathin manganite film

Cited by 18 publications

References 53 publications

Atomic-scale determination of spontaneous magnetic reversal in oxide heterostructures

Atomic-scale determination of spontaneous magnetic reversal in oxide heterostructures

Structural distortions at polar manganite interfaces

Artificial two-dimensional polar metal at room temperature

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