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- Films (6)
- Heterostructures (5)
- Interface (5)
- Oxide interfaces (5)
- Magnetoresistance (4)
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- Spin polarization (4)
- Augmented-wave method (3)
- Electroresistance (3)
- Magnetic tunnel junctions (3)
- Magnetocrystalline anisotropy (3)
- Polarization (3)
- Spin-orbit coupling (3)
- Spintronics (3)
- Thin-films (3)
- Antiferromagnetic (2)
- Antiperovskite (2)
- BaTiO3 (2)
- Band structure (2)
- Density functional theory (2)
- Dielectric polarisation (2)
- Electronic structure (2)
- Enhancement (2)
- Ferroelectric (2)
- Ferroelectric tunnel junctions (2)
- Ferroelectricity (2)
- First-principles (2)
- HfO2 (2)
- Insulators (2)
- Laalo3/Srtio3 interface (2)
- Magnetic anisotropy (2)
Articles 61 - 90 of 118
Full-Text Articles in Condensed Matter Physics
Emergent Vortices At A Ferromagnetic Superconducting Oxide Interface, Alexander Paul Petrović, A. Paré, Tula R. Paudel, K. Lee, S. Holmes, Crispin H. W. Barnes, A. David, T. Wu, Evgeny Y. Tsymbal, C. Panagopoulos
Emergent Vortices At A Ferromagnetic Superconducting Oxide Interface, Alexander Paul Petrović, A. Paré, Tula R. Paudel, K. Lee, S. Holmes, Crispin H. W. Barnes, A. David, T. Wu, Evgeny Y. Tsymbal, C. Panagopoulos
Evgeny Tsymbal Publications
Understanding the cohabitation arrangements of ferromagnetism and superconductivity at the LaAlO3/SrTiO3 interface remains an open challenge. Probing this coexistence with sub-Kelvin magnetotransport experiments, we demonstrate that a hysteretic in-plane magnetoresistance develops below the superconducting transition for H < 0.15 T, independently of the carrier density or oxygen annealing. This hysteresis is argued to arise from vortex depinning within a thin (< 20 nm) superconducting layer, mediated by discrete ferromagnetic dipoles located solely above the layer. The pinning strength may be modified by varying the superconducting channel thickness via electric field-effect doping. No evidence is found for bulk magnetism or finite-momentum pairing, and we conclude that ferromagnetism is strictly confined to the interface, where it competes with superconductivity. Our work indicates that oxide interfaces are ideal candidate materials for the growth and analysis of nanoscale superconductor/ferromagnet hybrids.
Chemically Induced Jahn–Teller Ordering On Manganite Surfaces, Zheng Gai, Wenzhi Lin, John D. Burton, K. Fuchigami, Paul C. Snijders, T. Z. Ward, Evgeny Y. Tsymbal, J. Shen, Stephen Jesse, Sergei V. Kalinin, Arthur P. Baddorf
Chemically Induced Jahn–Teller Ordering On Manganite Surfaces, Zheng Gai, Wenzhi Lin, John D. Burton, K. Fuchigami, Paul C. Snijders, T. Z. Ward, Evgeny Y. Tsymbal, J. Shen, Stephen Jesse, Sergei V. Kalinin, Arthur P. Baddorf
Evgeny Tsymbal Publications
Physical and electrochemical phenomena at the surfaces of transition metal oxides and their coupling to local functionality remains one of the enigmas of condensed matter physics. Understanding the emergent physical phenomena at surfaces requires the capability to probe the local composition, map order parameter fields and establish their coupling to electronic properties. Here we demonstrate that measuring the sub-30-pm displacements of atoms from high-symmetry positions in the atomically resolved scanning tunnelling microscopy allows the physical order parameter fields to be visualized in real space on the single-atom level. Here, this local crystallographic analysis is applied to the in-situ-grown manganite surfaces. …
Long-Range Electronic Reconstruction To A Dxz,Yz-Dominated Fermi Surface Below The Laalo3/Srtio3 Interface, Alexander Paul Petrović, A. Pare, Tula R. Paudel, K. Lee, S. Holmes, Crispin H. W. Barnes, A. David, T. Wu, Evgeny Y. Tsymbal, C. Panagopoulos
Long-Range Electronic Reconstruction To A Dxz,Yz-Dominated Fermi Surface Below The Laalo3/Srtio3 Interface, Alexander Paul Petrović, A. Pare, Tula R. Paudel, K. Lee, S. Holmes, Crispin H. W. Barnes, A. David, T. Wu, Evgeny Y. Tsymbal, C. Panagopoulos
Evgeny Tsymbal Publications
Low dimensionality, broken symmetry and easily-modulated carrier concentrations provoke novel electronic phase emergence at oxide interfaces. However, the spatial extent of such reconstructions - i.e. the interfacial ‘‘depth’’ - remains unclear. Examining LaAlO3/SrTiO3 heterostructures at previously unexplored carrier densities n2D 14 cm-2 , we observe a Shubnikov-de Haas effect for small in-plane fields, characteristic of an anisotropic 3D Fermi surface with preferential dxz,yz orbital occupancy extending over at least 100 nm perpendicular to the interface. Quantum oscillations from the 3D Fermi surface of bulk doped SrTiO3 emerge simultaneously at higher n2D. …
Interface States In Cofe2O4 Spin-Filter Tunnel Junctions, Pavel V. Lukashev, John D. Burton, Alexander Smogunov, Julian P. Velev, Evgeny Y. Tsymbal
Interface States In Cofe2O4 Spin-Filter Tunnel Junctions, Pavel V. Lukashev, John D. Burton, Alexander Smogunov, Julian P. Velev, Evgeny Y. Tsymbal
Evgeny Tsymbal Publications
Spin-filter tunneling is a promising way to generate highly spin-polarized current, a key component for spintronics applications. In this paper we explore the tunneling conductance across the spin-filter material CoFe2O4 interfaced with Au electrodes, a geometry which provides nearly perfect lattice matching at the CoFe2O4/Au(001) interface. Using density functional theory calculations we demonstrate that interface states play a decisive role in controlling the transport spin polarization in this tunnel junction. For a realistic CoFe2O4 barrier thickness, we predict a tunneling spin polarization of about −60%. We show that this value …
Polarization-Controlled Ohmic To Schottky Transition At A Metal/Ferroelectric Interface, Xiaohui Liu, Yong Wang, John D. Burton, Evgeny Y. Tsymbal
Polarization-Controlled Ohmic To Schottky Transition At A Metal/Ferroelectric Interface, Xiaohui Liu, Yong Wang, John D. Burton, Evgeny Y. Tsymbal
Evgeny Tsymbal Publications
Ferroelectric polar displacements have recently been observed in conducting electron-doped BaTiO3 (n-BTO). The coexistence of a ferroelectric phase and conductivity opens the door to new functionalities that may provide a unique route for novel device applications. Using first-principles methods and electrostatic modeling, we explore the effect that the switchable polarization of n-BTO has on the electronic properties of the SrRuO3/n-BTO (001) interface. Ferroelectric polarization controls the accumulation or depletion of electron charge at the interface, and the associated bending of the n-BTO conduction band determines the transport regime across the interface. The …
Polarization Discontinuity Induced Two-Dimensional Electron Gas At Zno/Zn(Mg)O Interfaces: A First-Principles Study, Jesuan Betancourt, J. J. Saavedra-Arias, John D. Burton, Yasuyuki Ishikawa, Evgeny Y. Tsymbal, Julian P. Velev
Polarization Discontinuity Induced Two-Dimensional Electron Gas At Zno/Zn(Mg)O Interfaces: A First-Principles Study, Jesuan Betancourt, J. J. Saavedra-Arias, John D. Burton, Yasuyuki Ishikawa, Evgeny Y. Tsymbal, Julian P. Velev
Evgeny Tsymbal Publications
The discovery of a high-mobility two-dimensional electron gas (2DEG) in wurtzite ZnO/Zn(Mg)O heterostructures is promising for applications due to the high mobility of the carriers. In this paper, we study the formation and properties of the 2DEG at ZnO/Zn(Mg)O interfaces using first-principles calculations based on hybrid density functional theory. The 2DEG arises from the polarization discontinuity at the interface between the two materials. The uncompensated bound charge at the interface gives rise to an electric field in the bulk of ZnO which confines free carriers close to the interface. We find that the type of the confined carriers is determined …
Anomalous And Spin Hall Effects In A Magnetic Tunnel Junction With Rashba Spin-Orbit Coupling, A. V. Vedyayev, M. S. Titova, N. V. Ryzhanova, M. Ye. Zhuravlev, Evgeny Y. Tsymbal
Anomalous And Spin Hall Effects In A Magnetic Tunnel Junction With Rashba Spin-Orbit Coupling, A. V. Vedyayev, M. S. Titova, N. V. Ryzhanova, M. Ye. Zhuravlev, Evgeny Y. Tsymbal
Evgeny Tsymbal Publications
Anomalous and spin Hall effects are investigated theoretically for a magnetic tunnel junction where the applied voltage produces a Rashba spin-orbit coupling within the tunneling barrier layer. The ferromagnetic electrodes are the source of the spin-polarized current. The tunneling electrons experience a spin-orbit coupling inside the barrier due to the applied electrical field. Charge and spin Hall currents are calculated as functions of the position inside the barrier and the angle between the magnetizations of the electrodes. We find that both charge and spin Hall currents are located inside the barrier near the interfaces. The dependence of the currents on …
Hydroxyl-Decorated Graphene Systems As Candidates For Organic Metal-Free Ferroelectrics, Multiferroics, And High-Performance Proton Battery Cathode Materials, Menghao Wu, John D. Burton, Evgeny Y. Tsymbal, Xiao Cheng Zeng, Purusottam Jena
Hydroxyl-Decorated Graphene Systems As Candidates For Organic Metal-Free Ferroelectrics, Multiferroics, And High-Performance Proton Battery Cathode Materials, Menghao Wu, John D. Burton, Evgeny Y. Tsymbal, Xiao Cheng Zeng, Purusottam Jena
Evgeny Tsymbal Publications
Using a first-principles method we show that graphene based materials, functionalized with hydroxyl groups, constitute a class of multifunctional, lightweight, and nontoxic organic materials with functional properties such as ferroelectricity, multiferroicity, and can be used as proton battery cathode materials. For example, the polarizations of semihydroxylized graphane and graphone, as well as fully hydroxylized graphane, are much higher than any organic ferroelectric materials known to date. Further, hydroxylized graphene nanoribbons with proton vacancies at the end can have much larger dipole moments. They may also be applied as high-capacity cathode materials with a specific capacity that is six times larger …
Ferroelectric Instability Under Screened Coulomb Interactions, Yong Wang, Xiaohui Liu, John D. Burton, Sitaram S. Jaswal, Evgeny Y. Tsymbal
Ferroelectric Instability Under Screened Coulomb Interactions, Yong Wang, Xiaohui Liu, John D. Burton, Sitaram S. Jaswal, Evgeny Y. Tsymbal
Evgeny Tsymbal Publications
We explore the effect of charge carrier doping on ferroelectricity using density functional calculations and phenomenological modeling. By considering a prototypical ferroelectric material, BaTiO3, we demonstrate that ferroelectric displacements are sustained up to the critical concentration of 0.11 electron per unit cell volume. This result is consistent with experimental observations and reveals that the ferroelectric phase and conductivity can coexist. Our investigations show that the ferroelectric instability requires only a short-range portion of the Coulomb force with an interaction range of the order of the lattice constant. These results provide a new insight into the origin of ferroelectricity …
New View Of The Occupied Band Structure Of Mo(112), Keisuke Fukutani, Hirokazu Hayashi, I. N. Yakovkin, Tula R. Paudel, Takafumi Habuchi, Daisuke Hirayama, Jian Jiang, Hideaki Iwasawa, Kenya Shimada, Ning Wu, Evgeny Y. Tsymbal, Yaroslav B. Losovyj, Peter A. Dowben
New View Of The Occupied Band Structure Of Mo(112), Keisuke Fukutani, Hirokazu Hayashi, I. N. Yakovkin, Tula R. Paudel, Takafumi Habuchi, Daisuke Hirayama, Jian Jiang, Hideaki Iwasawa, Kenya Shimada, Ning Wu, Evgeny Y. Tsymbal, Yaroslav B. Losovyj, Peter A. Dowben
Evgeny Tsymbal Publications
We present a comprehensive examination of the occupied surface-weighted band structure of Mo(112) along the two high-symmetry directions of the surface Brillouin zone, both from theoretical and experimental perspectives. The band structures are found to be significantly different for the states along the two high-symmetry directions and for the states with even and odd reflection parities with respect to the mirror planes. The present study suggests the existence of a number of surface-weighted bands along both high-symmetry directions. The complexity of the band structure near the Fermi level may impose potential difficulties in experimental determination of the electronphonon coupling parameters …
Ferroelectric And Multiferroic Tunnel Junctions, Evgeny Y. Tsymbal, Alexei Gruverman, Vincent Garcia, Manuel Bibes, A. Barthélémy
Ferroelectric And Multiferroic Tunnel Junctions, Evgeny Y. Tsymbal, Alexei Gruverman, Vincent Garcia, Manuel Bibes, A. Barthélémy
Evgeny Tsymbal Publications
The phenomenon of electron tunneling has been known since the advent of quantum mechanics, but continues to enrich our understanding of many fields of physics, as well as creating subfields on its own. Spin-dependent tunneling in magnetic tunnel junctions has aroused considerable interest and development. In parallel with this endeavor, recent advances in thin-film ferroelectrics have demonstrated the possibility of achieving stable and switchable ferroelectric polarization in nanometer-thick films. This discovery opened the possibility of using thin-film ferroelectrics as barriers in magnetic tunnel junctions, thus merging the fields of magnetism, ferroelectricity, and spin-polarized transport into an exciting and promising area …
Magnetic And Superconducting Phases At The Laalo3/Srtio3 Interface: The Role Of Interfacial Ti 3D Electrons, N. Pavlenko, Thilo Kopp, Evgeny Y. Tsymbal, George A. Sawatzky, Jochen Mannhart
Magnetic And Superconducting Phases At The Laalo3/Srtio3 Interface: The Role Of Interfacial Ti 3D Electrons, N. Pavlenko, Thilo Kopp, Evgeny Y. Tsymbal, George A. Sawatzky, Jochen Mannhart
Evgeny Tsymbal Publications
Ferromagnetism and superconductivity are, in most cases, adverse. However, recent experiments reveal that they coexist at interfaces of LaAlO3 and SrTiO3. We analyze the magnetic state within density functional theory and provide evidence that magnetism is not an intrinsic property of the two-dimensional electron liquid at the interface. We demonstrate that the robust ferromagnetic state is induced by the oxygen vacancies in SrTiO3 or in the LaAlO3 layer. This allows for the notion that areas with increased density of oxygen vacancies produce ferromagnetic puddles and account for the previous observation of a superparamagnetic behavior in …
Multiferroic Tunnel Junctions With Poly(Vinylidene Fluoride), Julian P. Velev, Juan M. López-Encarnación, John D. Burton, Evgeny Y. Tsymbal
Multiferroic Tunnel Junctions With Poly(Vinylidene Fluoride), Julian P. Velev, Juan M. López-Encarnación, John D. Burton, Evgeny Y. Tsymbal
Evgeny Tsymbal Publications
We perform first-principles calculations based on density functional theory of the spin-resolved conductance of poly(vinylidene fluoride)- (PVDF) based multiferroic tunnel junctions (MFTJs).We consider Co/PVDF/O/Co (0001) MFTJs with one oxidized interface, representing the different experimental growth conditions for the two interfaces. We demonstrate that this natural asymmetry leads to multiple resistance states associated with different magnetization configurations of the electrodes and ferroelectric polarization orientations of the barrier. Our results indicate very high tunability of the tunneling magnetoresistance and electroresistance effects, which could be useful for logic and memory applications.
Interface Dipole Effect On Thin Film Ferroelectric Stability: First-Principles And Phenomenological Modeling, Xiaohui Liu, Yong Wang, Pavel V. Lukashev, John D. Burton, Evgeny Y. Tsymbal
Interface Dipole Effect On Thin Film Ferroelectric Stability: First-Principles And Phenomenological Modeling, Xiaohui Liu, Yong Wang, Pavel V. Lukashev, John D. Burton, Evgeny Y. Tsymbal
Evgeny Tsymbal Publications
Utilization of the switchable spontaneous polarization of ferroelectric materials offers a promising avenue for the future of nanoelectronic memories and logic devices provided that nanoscale metal-ferroelectric-metal heterostructures can be engineered to maintain a bi-stable polarization switchable by an applied electric field. The most challenging aspect of this approach is to overcome the deleterious interface effects which tend to render ferroelectric polarization either unstable or unswitchable and which become ever more important as ferroelectric materials are produced thinner and thinner. Here we use first-principles density functional calculations and phenomenological modeling to demonstrate that a BaO/RuO2 interface termination sequence in SrRuO …
Coherent Potential Approximation As A Voltage Probe, Mikhail Ye. Zhuravlev, A. V. Vedyayev, Kirill D. Belashchenko, Evgeny Y. Tsymbal
Coherent Potential Approximation As A Voltage Probe, Mikhail Ye. Zhuravlev, A. V. Vedyayev, Kirill D. Belashchenko, Evgeny Y. Tsymbal
Evgeny Tsymbal Publications
Coherent potential approximation (CPA) haswidely been used for studying the residual resistivity of bulk alloys and electrical conductivity in systems with structural disorder. Here, we revisit the single-site CPA within the Landauer-Büttiker approach applied to the electronic transport in layered structures and show that thismethod can be interpreted in terms of the B¨uttiker voltage-probe model that has been developed for treating phase-breaking scattering in mesoscopic systems. We demonstrate that the on-site vertex function, which appears within the single-site CPA formalism, plays the role of the local chemical potential within the voltage-probe approach. This interpretation allows the determination of the chemical …
Intrinsic Defects In Multiferroic Bifeo3 And Their Effect On Magnetism, Tula R. Paudel, Sitaram S. Jaswal, Evgeny Y. Tsymbal
Intrinsic Defects In Multiferroic Bifeo3 And Their Effect On Magnetism, Tula R. Paudel, Sitaram S. Jaswal, Evgeny Y. Tsymbal
Evgeny Tsymbal Publications
We investigate the energetics of the intrinsic defects in bulk multiferroic BiFeO3 and explore their implication for magnetization using a first-principles approach based on density functional theory. We find that the dominant defects in oxidizing (oxygen-rich) conditions are Bi and Fe vacancies and in reducing (oxygen-poor) conditions are O and Bi vacancies. The calculated carrier concentration shows that the BiFeO3 grown in oxidizing conditions has p-type conductivity. The conductivity decreases with oxygen partial pressure, and the material becomes insulating with a tendency for n-type conductivity. We find that the Bi and Fe vacancies produce a magnetic …
Highly Spin-Polarized Conducting State At The Interface Between Nonmagnetic Band Insulators: Laalo3/Fes2 (001), John D. Burton, Evgeny Y. Tsymbal
Highly Spin-Polarized Conducting State At The Interface Between Nonmagnetic Band Insulators: Laalo3/Fes2 (001), John D. Burton, Evgeny Y. Tsymbal
Evgeny Tsymbal Publications
First-principles density functional calculations demonstrate that a spin-polarized two-dimensional conducting state can be realized at the interface between two nonmagnetic band insulators. The (001) surface of the diamagnetic insulator FeS2 (pyrite) supports a localized surface state deriving from Fe d orbitals near the conduction band minimum. The deposition of a few unit cells of the polar perovskite oxide LaAlO3 leads to electron transfer into these surface bands, thereby creating a conducting interface. The occupation of these narrow bands leads to an exchange splitting between the spin subbands, yielding a highly spin-polarized conducting state distinct from the rest of …
Tailoring A Two-Dimensional Electron Gas At The Laalo3 ∕ Srtio3 (001) Interface By Epitaxial Strain, C. W. Bark, D. A. Felker, Yong Wang, H. W. Jang, C. M. Folkman, J. W. Park, S. H. Baek, H. Zhou, D. D. Fong, X. Q. Pan, Evgeny Y. Tsymbal, M. S. Rzchowski, Chang-Beom Eom
Tailoring A Two-Dimensional Electron Gas At The Laalo3 ∕ Srtio3 (001) Interface By Epitaxial Strain, C. W. Bark, D. A. Felker, Yong Wang, H. W. Jang, C. M. Folkman, J. W. Park, S. H. Baek, H. Zhou, D. D. Fong, X. Q. Pan, Evgeny Y. Tsymbal, M. S. Rzchowski, Chang-Beom Eom
Evgeny Tsymbal Publications
Recently a metallic state was discovered at the interface between insulating oxides, most notably LaAlO3 and SrTiO3. Properties of this two-dimensional electron gas (2DEG) have attracted significant interest due to its potential applications in nanoelectronics. Control over this carrier density and mobility of the 2DEG is essential for applications of these unique systems, and may be achieved by epitaxial strain. However, despite the rich nature of strain effects on oxide materials properties, such as ferroelectricity, magnetism, and superconductivity, the relationship between the strain and electrical properties of the 2DEG at the LaAlO3∕SrTiO3 heterointerface remains …
Metallic And Insulating Oxide Interfaces Controlled By Electronic Correlations, H. W. Jang, D. A. Felker, C. W. Bark, Y. Wang, Manish K. Niranjan, C. T. Nelson, Y. Zhang, D. Su, C. M. Folkman, S. H. Baek, S. Lee, K. Janicka, Y. Zhu, X. Q. Pan, D. D. Fong, Evgeny Y. Tsymbal, M. S. Rzchowski, Chang-Beom Eom
Metallic And Insulating Oxide Interfaces Controlled By Electronic Correlations, H. W. Jang, D. A. Felker, C. W. Bark, Y. Wang, Manish K. Niranjan, C. T. Nelson, Y. Zhang, D. Su, C. M. Folkman, S. H. Baek, S. Lee, K. Janicka, Y. Zhu, X. Q. Pan, D. D. Fong, Evgeny Y. Tsymbal, M. S. Rzchowski, Chang-Beom Eom
Evgeny Tsymbal Publications
The formation of two-dimensional electron gases (2DEGs) at complex oxide interfaces is directly influenced by the oxide electronic properties. We investigated how local electron correlations control the 2DEG by inserting a single atomic layer of a rare-earth oxide (RO) [(R is lanthanum (La), praseodymium (Pr), neodymium (Nd), samarium (Sm), or yttrium (Y)] into an epitaxial strontium titanate oxide (SrTiO3) matrix using pulsed-laser deposition with atomic layer control. We find that structures with La, Pr, and Nd ions result in conducting 2DEGs at the inserted layer, whereas the structures with Sm or Y ions are insulating. Our local …
Transport Spin Polarization Of High-Curie Temperature Mnbi Films, Parashu Kharel, P. Thapa, Pavel V. Lukashev, Renat F. Sabirianov, Evgeny Y. Tsymbal, D. J. Sellmyer, Boris Nadgorny
Transport Spin Polarization Of High-Curie Temperature Mnbi Films, Parashu Kharel, P. Thapa, Pavel V. Lukashev, Renat F. Sabirianov, Evgeny Y. Tsymbal, D. J. Sellmyer, Boris Nadgorny
Evgeny Tsymbal Publications
We report on the study of the structural, magnetic, and transport properties of highly textured MnBi films with the Curie temperature of 628 K. In addition to detailed measurements of resistivity and magnetization, we measure transport spin polarization of MnBi by Andreev reflection spectroscopy and perform fully relativistic band-structure calculations of MnBi. A spin polarization from 51% ± 1% to 63% ± 1% is observed, consistent with the calculations and with an observation of a large magnetoresistance in MnBi contacts. The band-structure calculations indicate that in spite of almost identical densities of states at the Fermi energy, the large disparity …
A Giant Tunneling Electroresistance Effect Driven By Electrically Controlled Spin Valve At A Complex Oxide Interface, John D. Burton, Evgeny Y. Tsymbal
A Giant Tunneling Electroresistance Effect Driven By Electrically Controlled Spin Valve At A Complex Oxide Interface, John D. Burton, Evgeny Y. Tsymbal
Evgeny Tsymbal Publications
A giant tunneling electroresistance effect may be achieved in a ferroelectric tunnel junction by exploiting the magnetoelectric effect at the interface between the ferroelectric barrier and a magnetic La1-xSrxMnO3 electrode. Using first-principles density-functional theory we demonstrate that a few magnetic monolayers of La1-xSrxMnO3 near the interface act, in response to ferroelectric polarization reversal, as an atomic-scale spin valve by filtering spin-dependent current. This produces more than an order of magnitude change in conductance, and thus constitutes a giant resistive switching effect.
Interlayer Exchange Coupling Across A Ferroelectric Barrier, M. Ye. Zhuravlev, A. V. Vedyayev, Evgeny Y. Tsymbal
Interlayer Exchange Coupling Across A Ferroelectric Barrier, M. Ye. Zhuravlev, A. V. Vedyayev, Evgeny Y. Tsymbal
Evgeny Tsymbal Publications
A new magnetoelectric effect is predicted originating from the interlayer exchange coupling between two ferromagnetic layers separated by an ultrathin ferroelectric barrier. It is demonstrated that ferroelectric polarization switching driven by an external electric field leads to a sizable change in the interlayer exchange coupling. The effect occurs in asymmetric ferromagnet/ferroelectric/ferromagnet junctions due to a change in the electrostatic potential profile across the junction affecting the interlayer coupling. The predicted phenomenon indicates the possibility of switching the magnetic configuration by reversing the polarization of the ferroelectric barrier layer.
Electrically Driven Magnetism On A Pd Thin Film, Y. Sun, John D. Burton, Evgeny Y. Tsymbal
Electrically Driven Magnetism On A Pd Thin Film, Y. Sun, John D. Burton, Evgeny Y. Tsymbal
Evgeny Tsymbal Publications
Using first-principles density-functional calculations, we demonstrate that ferromagnetism can be induced and modulated on an otherwise paramagnetic Pd metal thin-film surface through application of an external electric field. As free charges are either accumulated or depleted at the Pd surface to screen the applied electric field, there is a corresponding change in the surface density of states. This change can be made sufficient for the Fermi-level density of states to satisfy the Stoner criterion, driving a transition locally at the surface from a paramagnetic state to an itinerant ferromagnetic state above a critical applied electric field, Ec. Furthermore, …
Effect Of Spin-Dependent Screening On Tunneling Electroresistance And Tunneling Magnetoresistance In Multiferroic Tunnel Junctions, M. Ye. Zhuravlev, S. Maekawa, Evgeny Y. Tsymbal
Effect Of Spin-Dependent Screening On Tunneling Electroresistance And Tunneling Magnetoresistance In Multiferroic Tunnel Junctions, M. Ye. Zhuravlev, S. Maekawa, Evgeny Y. Tsymbal
Evgeny Tsymbal Publications
Using a ferroelectric barrier as a functional material in a (magnetic) tunnel junction has recently attracted significant interest due to new functionalities not available in conventional tunnel junctions. Switching a ferroelectric polarization of the barrier alters conductance resulting in a tunneling electroresistance (TER) effect. Using a ferroelectric barrier in a magnetic tunnel junction makes it mutiferroic where TER coexists with tunneling magnetoresistance (TMR). Here we develop a simple model for a multiferroic tunnel junction (MFTJ) which consists of two ferromagnetic electrodes separated by a ferroelectric barrier layer. The model explicitly includes the spin-dependent screening potential and thus extends previously developed …
Ferroelectric Dead Layer Driven By A Polar Interface, Y. Wang, Manish K. Niranjan, K. Janicka, Julian P. Velev, Mikhail Ye Zhuravlev, Sitaram S. Jaswal, Evgeny Y. Tsymbal
Ferroelectric Dead Layer Driven By A Polar Interface, Y. Wang, Manish K. Niranjan, K. Janicka, Julian P. Velev, Mikhail Ye Zhuravlev, Sitaram S. Jaswal, Evgeny Y. Tsymbal
Evgeny Tsymbal Publications
Based on first-principles and model calculations we investigate the effect of polar interfaces on the ferroelectric stability of thin-film ferroelectrics. As a representative model, we consider a TiO2 -terminated BaTiO3 film with LaO monolayers at the two interfaces that serve as doping layers. We find that the polar interfaces create an intrinsic electric field that is screened by the electron charge leaking into the BaTiO3 layer. The amount of the leaking charge is controlled by the boundary conditions which are different for three heterostructures considered, namely, vacuum/LaO/BaTiO3 /LaO, LaO/BaTiO3 , and SrRuO3 /LaO/BaTiO3 …
Evolution Of The Band Alignment At Polar Oxide Interfaces, John D. Burton, Evgeny Y. Tsymbal
Evolution Of The Band Alignment At Polar Oxide Interfaces, John D. Burton, Evgeny Y. Tsymbal
Evgeny Tsymbal Publications
First-principles calculations demonstrate the evolution of the band alignment at La0.7A0.3MnO3 / La1−xAxO / TiO2 / SrTiO3 (001) heterointerfaces, where A=Ca, Sr, or Ba, as the interfacial A-site composition, La1−xAx, is varied from x=0.5 to x=1.0. This variation leads to a linear change in the SrTiO3 valence-band offset with respect to the Fermi level of the La0.7A0.3MnO3 metal electrode and hence to a linear change in the Schottky barrier height at this interface. The effect arises due to electrostatic …
Magnetoelectric Effect At The Srruo3/Batio3 (001) Interface: An Ab Initio Study, Manish K. Niranjan, John D. Burton, Julian P. Velev, Sitaram S. Jaswal, Evgeny Y. Tsymbal
Magnetoelectric Effect At The Srruo3/Batio3 (001) Interface: An Ab Initio Study, Manish K. Niranjan, John D. Burton, Julian P. Velev, Sitaram S. Jaswal, Evgeny Y. Tsymbal
Evgeny Tsymbal Publications
Ferromagnet/ferroelectric interface materials have emerged as structures with strong magnetoelectric coupling that may exist due to unconventional physical mechanisms. Here we present a first-principles study of the magnetoelectric effect at the ferromagnet/ferroelectric SrRuO3 /BaTiO3 (001) interface. We find that the exchange splitting of the spin-polarized band structure, and therefore the magnetization, at the interface can be altered substantially by reversal of the ferroelectric polarization in the BaTiO3. These magnetoelectric effects originate from the screening of polarization charges at the SrRuO3 /BaTiO3 interface and are consistent with the Stoner model for itinerant magnetism.
Tunneling Electroresistance In Ferroelectric Tunnel Junctions With A Composite Barrier, M. Ye. Zhuravlev, Yong Wang, S. Maekawa, Evgeny Y. Tsymbal
Tunneling Electroresistance In Ferroelectric Tunnel Junctions With A Composite Barrier, M. Ye. Zhuravlev, Yong Wang, S. Maekawa, Evgeny Y. Tsymbal
Evgeny Tsymbal Publications
Tunneling electroresistance (TER) effect is the change in the electrical resistance of a ferroelectric tunnel junction (FTJ) associated with polarization reversal in the ferroelectric barrier layer. Here we predict that a FTJ with a composite barrier that combines a functional ferroelectric film and a thin layer of a nonpolar dielectric can exhibit a significantly enhanced TER. Due to the change in the electrostatic potential with polarization reversal, the nonpolar dielectric barrier acts as a switch that changes its barrier height from a low to high value. The predicted values of TER are giant and indicate that the resistance of the …
Quantum Nature Of Two-Dimensional Electron Gas Confinement At Laalo3=Srtio3 Interfaces, Karolina Janicka, Julian P. Velev, Evgeny Y. Tsymbal
Quantum Nature Of Two-Dimensional Electron Gas Confinement At Laalo3=Srtio3 Interfaces, Karolina Janicka, Julian P. Velev, Evgeny Y. Tsymbal
Evgeny Tsymbal Publications
We perform density functional calculations to understand the mechanism controlling the confinement width of the two-dimensional electron gas (2DEG) at LaAlO3/SrTiO3 interfaces. We find that the 2DEG confinement can be explained by the formation of metal induced gap states (MIGS) in the band gap of SrTiO3. These states are formed as the result of quantum-mechanical tunneling of the charge created at the interface due to electronic reconstruction. The attenuation length of the MIGS into the insulator is controlled by the lowest-decay-rate evanescent states of SrTiO3, as determined by its complex band structure. Our …
First-Principles Studies Of A Two-Dimensional Electron Gas At The Interface In Ferroelectric Oxide Heterostructures, Yong Wang, Manish K. Niranjan, Sitaram S. Jaswal, Evgeny Y. Tsymbal
First-Principles Studies Of A Two-Dimensional Electron Gas At The Interface In Ferroelectric Oxide Heterostructures, Yong Wang, Manish K. Niranjan, Sitaram S. Jaswal, Evgeny Y. Tsymbal
Evgeny Tsymbal Publications
The discovery of a two-dimensional electron gas (2DEG) at the interface between two insulating oxides has recently stimulated intense research activity in this field. The 2DEG has unique properties that are promising for applications in all-oxide electronic devices.