Condensed Matter Physics Commons^™

Electrically Reversible Magnetization At The Antiperovskite/Perovskite Interface, Ding-Fu Shao, Gautam Gurung, Tula R. Paudel, Evgeny Y. Tsymbal

Evgeny Tsymbal Publications

Using density-functional calculations, we predict the emergence of electrically reversible magnetization at the interface between antiferromagnetic noncollinear antiperovskite GaNMn3 and ferroelectric perovskite BaTiO3. We find that Mn magnetic moments are enhanced and reoriented at the GaNMn3/ATiO3 (001) (A = Sr and Ba) interface, resulting in a sizable net magnetization along the [110] direction. This magnetization is reversed with ferroelectric polarization of BaTiO3 through ∼20◦ rotation of the noncollinear magnetic moments. The effect is driven by ferroelectric modulation of the antiferromagnetic exchange coupling between the interfacial Mn atoms mediated by the Mn-3d orbital population. Our results open opportunities for controlling the …

Radiation Tolerance In Nano-Structured Crystalline Fe(Cr)/Amorphous Sioc Composite, Qing Su, Tianyao Wang, Lin Shao, Michael Nastasi

Nebraska Center for Materials and Nanoscience: Faculty Publications

The management of irradiation defects is one of key challenges for structural materials in current and future reactor systems. To develop radiation tolerant alloys for service in extreme irradiation environments, the Fe self-ion radiation response of nanocomposites composed of amorphous silicon oxycarbide (SiOC) and crystalline Fe(Cr) were examined at 10, 20, and 50 displacements per atom damage levels. Grain growth in width direction was observed to increase with increasing irradiation dose in both Fe(Cr) films and Fe(Cr) layers in the nanocomposite after irradiation at room temperature. However, compared to the Fe(Cr) film, the Fe(Cr) layers in the nanocomposite exhibited ~50% …

Properties And Manipulation Of Ionic Liquid-Solid Interfaces In Complex Oxide Materials, Anthony Thomas Wong

Doctoral Dissertations

Ionic liquids are liquid salts that are bringing rapid changes to the field of solid electronic materials. The implementation of ionic liquids in conjunction with these solid materials produces interfacial effects, especially when a bias is applied across the ionic liquid, forming an electric double layer. Electric double layers in ionic liquids are unique in their formation and the interfacial charges that are orders of magnitude higher than conventional techniques they can impart, providing new techniques for device design and implementation. In chapter 1, the fundamentals of the solid state electronic and magnetic materials are introduced, along with ionic liquids, …

Artificial Quantum Many-Body States In Complex Oxide Heterostructures At Two-Dimensional Limit, Xiaoran Liu

Graduate Theses and Dissertations

As the representative family of complex oxides, transition metal oxides, where the lattice,

charge, orbital and spin degrees of freedom are tightly coupled, have been at the forefront

of condensed matter physics for decades. With the advancement of state-of-the-art heteroepitaxial deposition techniques, it has been recognized that combining these oxides on the atomic scale, the interfacial region offers great opportunities to discover emergent phenomena and tune materials' functionality. However, there still lacks general guiding principles for experimentalists, following which one can design and fabricate artificial systems on demand. The main theme of this dissertation is to devise and propose some …

Tunneling Anisotropic Magnetoresistance In A Magnetic Tunnel Junction With Half-Metallic Electrodes, John D. Burton, Evgeny Y. Tsymbal

Evgeny Tsymbal Publications

Tunneling anisotropic magnetoresistance (TAMR) is the difference in resistance of a magnetic tunnel junction due to a change in magnetization direction of one or both magnetic electrodes with respect to the flow of current. We present the results of first-principles density functional calculations of the TAMR effect in magnetic tunnel junctions with La_0.7Sr_0.3MnO₃ (LSMO) electrodes and a SrTiO₃ (STO) tunneling barrier. We find an ∼500% difference in resistance between magnetization in the plane and out of the plane. This large TAMR effect originates from the half-metallic nature of LSMO: When magnetization is out of …

Electric Control Of Spin Injection Into A Ferroelectric Semiconductor, Xiaohui Liu, John D. Burton, M. Ye. Zhuravlev, Evgeny Y. Tsymbal

Evgeny Tsymbal Publications

Electric-field control of spin-dependent properties has become one of the most attractive phenomena in modern materials research due to the promise of new device functionalities. One of the paradigms in this approach is to electrically toggle the spin polarization of carriers injected into a semiconductor using ferroelectric polarization as a control parameter. Using first-principles density-functional calculations, we explore the effect of ferroelectric polarization of electron-doped BaTiO₃ (n-BaTiO₃) on the spin-polarized transmission across the SrRuO₃/n-BaTiO₃(001) interface. Our study reveals that, in this system, the interface transmission is negatively spin polarized …

Ferroelectric Polarization Dependent Interface Effects, Xiaohui Liu

Department of Physics and Astronomy: Dissertations, Theses, and Student Research

Utilization of the switchable spontaneous polarization of nanometer scale ferroelectric materials offers a promising avenue for future nanoelectronic devices. In this dissertation, we use density-functional calculations and phenomenological modeling to explore the effects of interface termination on thin-film heterostructures, the effects of electron doping in bulk ferroelectric materials on ferroelectric stability, and the effects of ferroelectric polarization switching on the electronic and transport properties of interfaces.

For SrRuO₃/BaTiO₃/SrRuO₃ epitaxial heterostructures grown on SrTiO₃, we find that the built-in dipole at the BaO/RuO₂ terminated interface leads to a strong preference for one polarization. …

Ferroelectric Tunnel Junctions With Graphene Electrodes, Haidong Lu, Alexey Lipatov, Sangjin Ryu, D. J. Kim, H. Lee, M. Ye. Zhuravlev, Chang-Beom Eom, Evgeny Y. Tsymbal, Alexander Sinitskii, Alexei Gruverman

Evgeny Tsymbal Publications

Polarization-driven resistive switching in ferroelectric tunnel junctions (FTJs)—structures composed of two electrodes separated by an ultrathin ferroelectric barrier—offers new physics and materials functionalities, as well as exciting opportunities for the next generation of non-volatile memories and logic devices. Performance of FTJs is highly sensitive to the electrical boundary conditions, which can be controlled by electrode material and/or interface engineering. Here, we demonstrate the use of graphene as electrodes in FTJs that allows control of interface properties for significant enhancement of device performance. Ferroelectric polarization stability and resistive switching are strongly affected by a molecular layer at the graphene/BaTiO₃ interface. …

Influence Of Quantum Dot Structure On The Optical Properties Of Group Iv Materials Fabricated By Ion Implantation, Eric G. Barbagiovanni

Electronic Thesis and Dissertation Repository

In nanostructures (NSs), to acquire a fundamental understanding of the electronic states by studying the optical properties is inherently complicated. A widely used simplification to this problem comes about by developing a model for a small scale representation of types of NSs and applying it to a hierarchy of fabrication methods. However, this methodology fails to account for structural differences incurred by the fabrication method that lead to differences in the optical properties. Proper modelling is realized by first considering the proper range of experimental parameters individually as inputs to a theoretical model and applying the correct parameters to the …

Interface Effects In Spin-Dependent Tunneling, Evgeny Y. Tsymbal, Kirill D. Belashchenko, Julian P. Velev, Sitaram Jaswal, Mark Van Schilfgaarde, Ivan I. Oleynik, Derek A. Stewart

Evgeny Tsymbal Publications

In the past few years the phenomenon of spin dependent tunneling (SDT) in magnetic tunnel junctions (MTJs) has aroused enormous interest and has developed into a vigorous field of research. The large tunneling magnetoresistance (TMR) observed in MTJs garnered much attention due to possible application in random access memories and magnetic field sensors. This led to a number of fundamental questions regarding the phenomenon of SDT. One such question is the role of interfaces in MTJs and their effect on the spin polarization of the tunneling current and TMR. In this paper we consider different models which suggest that the …