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Articles 271 - 300 of 479
Full-Text Articles in Condensed Matter Physics
Scaling Of Electroresistance Effect In Fully Integrated Ferroelectric Tunnel Junctions, Mohammad Abuwasib, Haidong Lu, Tao Li, Pratyush Buragohain, Hyungwoo Lee, Chang-Beom Eom, Alexei Gruverman, Uttam Singisetti
Scaling Of Electroresistance Effect In Fully Integrated Ferroelectric Tunnel Junctions, Mohammad Abuwasib, Haidong Lu, Tao Li, Pratyush Buragohain, Hyungwoo Lee, Chang-Beom Eom, Alexei Gruverman, Uttam Singisetti
Alexei Gruverman Publications
Systematic investigation of the scalability for tunneling electroresistance (TER) of integrated Co/BaTiO3/SrRuO3 ferroelectric tunnel junctions (FTJs) has been performed from micron to deep submicron dimensions. Pulsed measurements of the transient currents confirm the ferroelectric switching behavior of the FTJs, while the hysteresis loops measured by means of piezoresponse force microscopy verify the scalability of these structures. Fully integrated functional FTJ devices with the size of 300×300 nm2 exhibiting a tunneling electroresistance (TER) effect of the order of 2.7×104% have been fabricated and tested. Measured current density of 75 A/cm2 for the ON state …
Domain Wall Conductivity In Semiconducting Hexagonal Ferroelectric Tbmno3 Thin Films, D. J. Kim, J. G. Connell, S. S. A. Seo, Alexei Gruverman
Domain Wall Conductivity In Semiconducting Hexagonal Ferroelectric Tbmno3 Thin Films, D. J. Kim, J. G. Connell, S. S. A. Seo, Alexei Gruverman
Alexei Gruverman Publications
Although enhanced conductivity of ferroelectric domain boundaries has been found in BiFeO3 and Pb(Zr,Ti)O3 films as well as hexagonal rare-earth manganite single crystals, the mechanism of the domain wall conductivity is still under debate. Using conductive atomic force microscopy, we observe enhanced conductance at the electrically-neutral domain walls in semiconducting hexagonal ferroelectric TbMnO3 thin films where the structure and polarization direction are strongly constrained along the c-axis. This result indicates that domain wall conductivity in ferroelectric rare-earth manganites is not limited to charged domain walls. We show that the observed conductivity in the TbMnO3 films is …
Anisotropy, Phonon Modes, And Free Charge Carrier Parameters In Monoclinic Β-Gallium Oxide Single Crystals, Mathias Schubert, Rafal Korlacki, Sean Knight, Tino Hofmann, Stefan Schöche, Vanya Darakchieva, Erik Janzén, Bo Monemar, Daniela Gogova, Q.-T. Thieu, R. Togashi, H. Murakami, Yoshinao Kumagai, Ken Goto, Akito Kuramata, S. Yamakoshi, Masataka Higashiwaki
Anisotropy, Phonon Modes, And Free Charge Carrier Parameters In Monoclinic Β-Gallium Oxide Single Crystals, Mathias Schubert, Rafal Korlacki, Sean Knight, Tino Hofmann, Stefan Schöche, Vanya Darakchieva, Erik Janzén, Bo Monemar, Daniela Gogova, Q.-T. Thieu, R. Togashi, H. Murakami, Yoshinao Kumagai, Ken Goto, Akito Kuramata, S. Yamakoshi, Masataka Higashiwaki
Department of Electrical and Computer Engineering: Faculty Publications
We derive a dielectric function tensor model approach to render the optical response of monoclinic and triclinic symmetry materials with multiple uncoupled infrared and far-infrared active modes. We apply our model approach to monoclinic β-Ga2O3 single-crystal samples. Surfaces cut under different angles from a bulk crystal, (010) and (2̅01), are investigated by generalized spectroscopic ellipsometry within infrared and far-infrared spectral regions. We determine the frequency dependence of 4 independent β-Ga2O3 Cartesian dielectric function tensor elements by matching large sets of experimental data using a point-by-point data inversion approach. From matching our monoclinic …
Ferroelectric Polymer Nanopillar Arrays On Flexible Substrates By Reverse Nanoimprint Lithography, Jingfeng Song, Haidong Lu, Keith Foreman, Shumin Li, Li Tan, Shireen Adenwalla, Alexei Gruverman, Stephen Ducharme
Ferroelectric Polymer Nanopillar Arrays On Flexible Substrates By Reverse Nanoimprint Lithography, Jingfeng Song, Haidong Lu, Keith Foreman, Shumin Li, Li Tan, Shireen Adenwalla, Alexei Gruverman, Stephen Ducharme
Stephen Ducharme Publications
With the increasing interest in deploying ferroelectric polymer in flexible electronics and electromechanics, high-throughput and low-cost fabrication of 3D ferroelectric polymer nanostructures on flexible substrates can be a significant basis for future research and applications. Here, we report that large arrays of ferroelectric polymer nanopillars can be prepared directly on soft, flexible substrates by using low-cost polydimethylsiloxane (PDMS) soft-mold reverse nanoimprint lithography at 135 °C and at pressures as low as 3 bar. The nanopillar arrays were highly uniform over large areas of at least 200 × 200 μm and had good crystallinity with nearly optimum (110) orientation. Furthermore, the …
2d Cocrystallization From H‑Bonded Organic Ferroelectrics, Donna A. Kunkel, James Hooper, Benjamin Bradley, Lisa Schlueter, Tom Rasmussen, Paulo Costa, Sunit Beniwal, Stephen Ducharme, Eva Zurek, Axel Enders
2d Cocrystallization From H‑Bonded Organic Ferroelectrics, Donna A. Kunkel, James Hooper, Benjamin Bradley, Lisa Schlueter, Tom Rasmussen, Paulo Costa, Sunit Beniwal, Stephen Ducharme, Eva Zurek, Axel Enders
Stephen Ducharme Publications
The synthesis of 2D H-bonded cocrystals from the room-temperature ferroelectric organics croconic acid (CA) and 3-hydroxyphenalenone (3-HPLN) is demonstrated through self-assembly on a substrate under ultrahigh vacuum. 2D cocrystal polymorphs of varied stoichiometry were identified with scanning tunneling microscopy, and one of the observed structural building blocks consists of two CA and two 3-HPLN molecules. Computational analysis with density functional theory confirmed that the experimental (CA)2(3-HPLN)2 tetramers are lower in energy than single-component structures due to the ability of the tetramers to pack efficiently in two dimensions, the promotion of favorable electrostatic interactions between tetramers, and the …
Fabrication Of Diisopropylammonium Bromide Aligned Microcrystals With In-Plane Uniaxial Polarization, Shashi Poddar, Haidong Lu, Jingfeng Song, Om Goit, Shah Valloppilly, Alexei Gruverman, Stephen Ducharme
Fabrication Of Diisopropylammonium Bromide Aligned Microcrystals With In-Plane Uniaxial Polarization, Shashi Poddar, Haidong Lu, Jingfeng Song, Om Goit, Shah Valloppilly, Alexei Gruverman, Stephen Ducharme
Stephen Ducharme Publications
Textured arrays of ferroelectric microcrystals of diisopropylammonium bromide were grown from solution at room temperature onto silicon substrates and studied by means of x-ray diffraction, atomic force microscopy, electron microscopy, and piezoresponse force microscopy. The needle-shaped crystals had dimensions of approximately 50 μm × 5 μm in the plane and were approximately 200 nm thick, where the dimensions and arrangement were influenced by growth conditions. The observations suggest an Ostwald ripening mechanism of the microcrystal growth. The crystals had the structure of the ferroelectric phase, where the polarization axis was in-plane and parallel to the long axis of …
The Metal/Organic Interface In Cobalt/Vinylidene Fluoride Heterostructures, Keith Foreman, E Echeverria, Mark A. Koten, R. M. Lindsay, N. Hong, Jeffrey E. Shield, Shireen Adenwalla
The Metal/Organic Interface In Cobalt/Vinylidene Fluoride Heterostructures, Keith Foreman, E Echeverria, Mark A. Koten, R. M. Lindsay, N. Hong, Jeffrey E. Shield, Shireen Adenwalla
Shireen Adenwalla Papers
Organic-based electronic devices are rapidly increasing in popularity, making it essential to understand and characterize the interface between organic materials and metallic electrodes. This work reports on the characterization of the interface between thin films of an emerging organic ferroelectric, vinylidene fluoride (VDF) oligomer, and Co, an important high Curie temperature ferromagnet. Using a wide battery of experimental techniques, it is shown that VDF oligomer thin films as thin as 15 nm can halt, or prevent, Co oxidization in atmospheric conditions, a necessary condition for device applications. Selectivity of magnetic properties, such as remanent magnetization, is enabled by the clarification …
Ferroelectric Characterization And Growth Optimization Of Thermally Evaporated Vinylidene Fluoride Thin Films, Keith Foreman, N. Hong, C. Labedz, C. Shearer, Stephen Ducharme, Shireen Adenwalla
Ferroelectric Characterization And Growth Optimization Of Thermally Evaporated Vinylidene Fluoride Thin Films, Keith Foreman, N. Hong, C. Labedz, C. Shearer, Stephen Ducharme, Shireen Adenwalla
Shireen Adenwalla Papers
Organic thin films have numerous advantages over inorganics in device processing and price. The large polarization of the organic ferroelectric oligomer vinylidene fluoride (VDF) could prove useful for both device applications and the investigation of fundamental physical phenomena. A VDF oligomer thin film vacuum deposition process, such as thermal evaporation, preserves film and interface cleanliness, but is challenging, with successful deposition occurring only within a narrow parameter space. We report on the optimal deposition parameters for VDF oligomer thin films, refining the parameter space for successful deposition, resulting in a high yield of robust ferroelectric films. In particular, we investigate …
Theory Of Magnon Motive Force In Chiral Ferromagnets, Utkan Güngördü, Alexey Kovalev
Theory Of Magnon Motive Force In Chiral Ferromagnets, Utkan Güngördü, Alexey Kovalev
Department of Physics and Astronomy: Faculty Publications
We predict that magnon motive force can lead to temperature dependent, nonlinear chiral damping in both conducting and insulating ferromagnets. We estimate that this damping can significantly influence the motion of skyrmions and domain walls at finite temperatures. We also find that in systems with low Gilbert damping moving chiral magnetic textures and resulting magnon motive forces can induce large spin and energy currents in the transverse direction.
Stability Of Skyrmion Lattices And Symmetries Of Quasi-Two-Dimensional Chiral Magnets, Utkan Güngördü, Rabindra Nepal, Oleg A. Tretiakov, Kirill D. Belashchenko, Alexey Kovalev
Stability Of Skyrmion Lattices And Symmetries Of Quasi-Two-Dimensional Chiral Magnets, Utkan Güngördü, Rabindra Nepal, Oleg A. Tretiakov, Kirill D. Belashchenko, Alexey Kovalev
Department of Physics and Astronomy: Faculty Publications
Recently there has been substantial interest in realizations of skyrmions, in particular in quasi-two-dimensional (2D) systems due to increased stability resulting from reduced dimensionality. A stable skyrmion, representing the smallest realizable magnetic texture, could be an ideal element for ultradense magnetic memories. Here we use the most general form of the quasi-2D free energy with Dzyaloshinskii-Moriya interactions constructed from general symmetry considerations reflecting the underlying system. We predict that the skyrmion phase is robust and it is present even when the system lacks the in-plane rotational symmetry. In fact, the lowered symmetry leads to increased stability of vortex-antivortex lattices with …
Magnetoelectric Domain Wall Dynamics And Its Implications For Magnetoelectric Memory, Kirill D. Belashchenko, Oleg Tchernyshyov, Alexey Kovalev, Oleg A. Tretiakov
Magnetoelectric Domain Wall Dynamics And Its Implications For Magnetoelectric Memory, Kirill D. Belashchenko, Oleg Tchernyshyov, Alexey Kovalev, Oleg A. Tretiakov
Department of Physics and Astronomy: Faculty Publications
Domain wall dynamics in a magnetoelectric antiferromagnet is analyzed, and its implications for magnetoelectric memory applications are discussed. Cr2O3 is used in the estimates of the materials parameters. It is found that the domain wall mobility has a maximum as a function of the electric field due to the gyrotropic coupling induced by it. In Cr2O3, the maximal mobility of 0.1 m/(s Oe) is reached at E = 0.06 V/nm. Fields of this order may be too weak to overcome the intrinsic depinning field, which is estimated for B-doped Cr2O3 …
Hexagonal Rare-Earth Manganites As Promising Photovoltaics And Light Polarizers, Xin Huang, Tula R. Paudel, Shuai Dong, Evgeny Y. Tsymbal
Hexagonal Rare-Earth Manganites As Promising Photovoltaics And Light Polarizers, Xin Huang, Tula R. Paudel, Shuai Dong, Evgeny Y. Tsymbal
Evgeny Tsymbal Publications
Ferroelectric materials possess a spontaneous electric polarization and may be utilized in various technological applications ranging from nonvolatile memories to solar cells and light polarizers. Recently, hexagonal rareearth manganites, h-RMnO3 (R is a rare-earth ion), have attracted considerable interest due to their intricate multiferroic properties and improper ferroelectricity characterized by a sizable remnant polarization and high Curie temperature. Here we demonstrate that these compounds can serve as very efficient photovoltaic materials and, in addition, possess remarkable optical anisotropy properties. Using first-principles methods based on density functional theory and considering h-TbMnO3 as a representative …
Contact Resistance To Srruo3 And La0.67Sr0.33Mno3 Epitaxial Films, Mohammad Abuwasib, Hyungwoo Lee, Alexei Gruverman, Chang-Beom Eom, Uttam Singisetti
Contact Resistance To Srruo3 And La0.67Sr0.33Mno3 Epitaxial Films, Mohammad Abuwasib, Hyungwoo Lee, Alexei Gruverman, Chang-Beom Eom, Uttam Singisetti
Alexei Gruverman Publications
Contact resistance to the metallic oxide electrodes, SrRuO3 (SRO) and La0.67Sr0.33MnO3 (LSMO), is an important parameter that affects the ferroelectric tunnel junction (FTJ) device performance. We have systematically studied the contact resistance between metallic oxide electrodes (SRO, LSMO) and contact metal overlayers (Ti, Pt) after exposure to various processing environments. Specific contact resistivity (ρc) for Ti and Pt contact metals and the sheet resistance (Rsh) of the metallic oxides are measured after exposure to different reactive ion plasma process steps. Sheet resistance degradation was observed for both SRO and …
Effect Of Sm Content On Energy Product Of Rapidly Quenched And Oriented Smco5 Ribbons, Wenyong Zhang, Xingzhong Li, Shah R. Valloppilly
Effect Of Sm Content On Energy Product Of Rapidly Quenched And Oriented Smco5 Ribbons, Wenyong Zhang, Xingzhong Li, Shah R. Valloppilly
Nebraska Center for Materials and Nanoscience: Faculty Publications
The Sm-content dependence of phase composition, anisotropy, and other magnetic properties of Sm1+δCo5 (δ ≤ 0.12) ribbons melt spun at 10 m/s has been studied. The samples consist of hexagonal SmCo5 grains whose c axes are preferentially aligned along the long direction of the ribbon. The lattice parameter a and the cell volume (V) increase with increasing Sm content δ, whereas c decreases. Sm addition appears to improve the degree of the preferred orientation of the c-axis and to increase the mean grain size, which weakens the effective intergranular exchange …
Reconfigurable Large-Area Magnetic Vortex Circulation Patterns, Robert Streubel, Florian Kronast, Ulrich K. Rößler, Oliver G. Schmidt, Denys Makarov
Reconfigurable Large-Area Magnetic Vortex Circulation Patterns, Robert Streubel, Florian Kronast, Ulrich K. Rößler, Oliver G. Schmidt, Denys Makarov
Robert Streubel Papers
Magnetic vortices in nanodots own a switchable circulation sense. These nontrivial magnetization configurations can be arranged into extended and interacting patterns. We have experimentally created large arrays of magnetically reconfigurable vortex patterns in nonplanar honeycomb lattices using particle lithography. Optimizing height asymmetry of the vertices and applying an in-plane magnetic field provide means to switch between homocircular and staggered vortex patterns with a potentially high impact on magnonics and spintronics relying on chiral noncollinear spin textures. To this end, exchange coupling of extended vortex lattices with an out-of-plane magnetized layer allows one to realize artificial skyrmionic core textures with controllable …
Magnetization Dynamics Of Imprinted Non-Collinear Spin Textures, Robert Streubel, Peter Fischer, Martin Kopte, Oliver G. Schmidt, Denys Makarov
Magnetization Dynamics Of Imprinted Non-Collinear Spin Textures, Robert Streubel, Peter Fischer, Martin Kopte, Oliver G. Schmidt, Denys Makarov
Robert Streubel Papers
We study the magnetization dynamics of non-collinear spin textures realized via imprint of the magnetic vortex state in soft permalloy into magnetically hard out-of-plane magnetized Co/Pd nanopatterned heterostructures. Tuning the interlayer exchange coupling between soft- and hard-magnetic subsystems provides means to tailor the magnetic state in the Co/Pd stack from being vortex- to donut-like with different core sizes. While the imprinted vortex spin texture leads to the dynamics similar to the one observed for vortices in permalloy disks, the donut-like state causes the appearance of two gyrofrequencies characteristic of the early and later stages of the magnetization dynamics. The dynamics …
Nanomechanics Of Flexoelectric Switching, J. Očenášek, Haidong Lu, C. W. Bark, Chang-Beom Eom, J. Alcalá, G. Catalan, Alexei Gruverman
Nanomechanics Of Flexoelectric Switching, J. Očenášek, Haidong Lu, C. W. Bark, Chang-Beom Eom, J. Alcalá, G. Catalan, Alexei Gruverman
Materials Research Science and Engineering Center: Faculty Publications
We examine the phenomenon of flexoelectric switching of polarization in ultrathin films of barium titanate induced by a tip of an atomic force microscope (AFM). The spatial distribution of the tip-induced flexoelectricity is computationally modeled both for perpendicular mechanical load (point measurements) and for sliding load (scanning measurements), and compared with experiments. We find that (i) perpendicular load does not lead to stable ferroelectric switching in contrast to the load applied in the sliding contact load regime, due to nontrivial differences between the strain distributions in both regimes: ferroelectric switching for the perpendicular load mode is impaired by a strain …
Retrieving Spin Textures On Curved Magnetic Thin Films With Full-Field Soft X-Ray Microscopies, Robert Streubel, Florian Kronast, Peter Fischer, Dula Parkinson, Oliver G. Schmidt, Denys Makarov
Retrieving Spin Textures On Curved Magnetic Thin Films With Full-Field Soft X-Ray Microscopies, Robert Streubel, Florian Kronast, Peter Fischer, Dula Parkinson, Oliver G. Schmidt, Denys Makarov
Robert Streubel Papers
X-ray tomography is a well-established technique to characterize 3D structures in material sciences and biology; its magnetic analogue - magnetic X-ray tomography - is yet to be developed. Here we demonstrate the visualization and reconstruction of magnetic domain structures in a 3D curved magnetic thin films with tubular shape by means of full-field soft X-ray microscopies. The 3D arrangement of the magnetization is retrieved from a set of 2D projections by analysing the evolution of the magnetic contrast with varying projection angle. Using reconstruction algorithms to analyse the angular evolution of 2D projections provides quantitative information about domain patterns and …
Titanium Trisulfide Monolayer: Theoretical Prediction Of A New Direct-Gap Semiconductor With High And Anisotropic Carrier Mobility, Jun Dai, Xiao Cheng Zeng
Titanium Trisulfide Monolayer: Theoretical Prediction Of A New Direct-Gap Semiconductor With High And Anisotropic Carrier Mobility, Jun Dai, Xiao Cheng Zeng
Xiao Cheng Zeng Publications
A new two-dimensional (2D) layered material, namely, titanium trisulfide (TiS3) monolayer, is predicted to possess novel electronic properties. Ab initio calculations show that the perfect TiS3 monolayer is a direct-gap semiconductor with a bandgap of 1.02 eV, close to that of bulk silicon, and with high carrier mobility. More remarkably, the in-plane electron mobility of the 2D TiS3 is highly anisotropic, amounting to about 10,000 cm2 V−1 s−1 in the b direction, which is higher than that of the MoS2 monolayer, whereas the hole mobility is about two orders of magnitude lower. …
Enhancement Of Local Piezoresponse In Polymer Ferroelectrics Via Nanoscale Control Of Microstructure, Yoon-Young Choi, Pankaj Sharma, Charudatta Phatak, David J. Gosztola, Yunya Liu, Joonseok Lee, Byeongdu Lee, Jiangyu Li, Alexei Gruverman, Stephen Ducharme, Seungbum Hong
Enhancement Of Local Piezoresponse In Polymer Ferroelectrics Via Nanoscale Control Of Microstructure, Yoon-Young Choi, Pankaj Sharma, Charudatta Phatak, David J. Gosztola, Yunya Liu, Joonseok Lee, Byeongdu Lee, Jiangyu Li, Alexei Gruverman, Stephen Ducharme, Seungbum Hong
Stephen Ducharme Publications
Polymer ferroelectrics are flexible and lightweight electromechanical materials that are widely studied due to their potential application as sensors, actuators, and energy harvesters. However, one of the biggest challenges is their low piezoelectric coefficient. Here, we report a mechanical annealing effect based on local pressure induced by a nanoscale tip that enhances the local piezoresponse. This process can control the nanoscale material properties over a microscale area at room temperature. We attribute this improvement to the formation and growth of β-phase extended chain crystals via sliding diffusion and crystal alignment along the scan axis under high mechanical stress. We believe …
Electric Control Of Spin Injection Into A Ferroelectric Semiconductor, Xiaohui Liu, John D. Burton, M. Ye. Zhuravlev, Evgeny Y. Tsymbal
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 …
Magnetic Force Microscopy Study Of Zr2co11-Based Nanocrystalline Materials: Effect Of Mo Addition, Lanping Yue, Yunlong Jin, Wenyong Zhang, David J. Sellmyer
Magnetic Force Microscopy Study Of Zr2co11-Based Nanocrystalline Materials: Effect Of Mo Addition, Lanping Yue, Yunlong Jin, Wenyong Zhang, David J. Sellmyer
Nebraska Center for Materials and Nanoscience: Faculty Publications
The addition of Molybdenum was used to modify the nanostructure and enhance coercivity of rare-earth-free Zr2Co11-based nanocrystalline permanent magnets. The effect of Mo addition on magnetic domain structures of melt spun nanocrystalline Zr16Co84−xMox (𝑥 = 0, 0.5, 1, 1.5, and 2.0) ribbons has been investigated. It was found that magnetic properties and local domain structures are strongly influenced by Mo doping. The coercivity of the samples increases with the increase in Mo content (𝑥 ≤ 1.5). The maximum energy product (𝐵𝐻)max increases with increasing 𝑥 from 0.5 MGOe for 𝑥 …
Magnetic Chiral Spin Textures By Imprinting, Robert Streubel, F. Kronast, U. Rössler, O. G. Schmidt, P. Fischer, D. Makarov
Magnetic Chiral Spin Textures By Imprinting, Robert Streubel, F. Kronast, U. Rössler, O. G. Schmidt, P. Fischer, D. Makarov
Robert Streubel Papers
The unique properties of non-trivial topological states, e.g. magnetic skyrmions [1] may path the way towards novel spintronic devices [2]. However, these spin textures have only been observed in special classes of materials possessing non-centrosymmetric crystal structure [1,3-6] and at low temperatures, which limits their application potential. We offer an alternate route to design synthetic magnetic heterostructures that resemble swirls, vortices or skyrmions with distinct topological charge densities at room temperature. By vertically stacking two magnetic nanopatterns with in-and out-of-plane magnetization and tailoring the interlayer exchange coupling, non-collinear spin textures with tunable topological charge can be imprinted (Fig. 1a).
Manipulating Topological States By Imprinting Non-Collinear Spin Textures, Robert Streubel, Luyang Han, Mi Young Im, Florian Kronast, Ulrich K. Rößler, Florin Radu, Radu Abrudan, Gungun Lin, Oliver G. Schmidt, Peter Fischer, Denys Makarov
Manipulating Topological States By Imprinting Non-Collinear Spin Textures, Robert Streubel, Luyang Han, Mi Young Im, Florian Kronast, Ulrich K. Rößler, Florin Radu, Radu Abrudan, Gungun Lin, Oliver G. Schmidt, Peter Fischer, Denys Makarov
Robert Streubel Papers
Topological magnetic states, such as chiral skyrmions, are of great scientific interest and show huge potential for novel spintronics applications, provided their topological charges can be fully controlled. So far skyrmionic textures have been observed in noncentrosymmetric crystalline materials with low symmetry and at low temperatures. We propose theoretically and demonstrate experimentally the design of spin textures with topological charge densities that can be tailored at ambient temperatures. Tuning the interlayer coupling in vertically stacked nanopatterned magnetic heterostructures, such as a model system of a Co/Pd multilayer coupled to Permalloy, the in-plane non-collinear spin texture of one layer can be …
Effect Of Strain On Ferroelectric Field Effect In Strongly Correlated Oxide Sm0.5Nd0.5Nio3, Le Zhang, Chen, H. J. Gardner, Mark A. Koten, Jeffrey E. Shield, Xia Hong
Effect Of Strain On Ferroelectric Field Effect In Strongly Correlated Oxide Sm0.5Nd0.5Nio3, Le Zhang, Chen, H. J. Gardner, Mark A. Koten, Jeffrey E. Shield, Xia Hong
Nebraska Center for Materials and Nanoscience: Faculty Publications
We report the effect of epitaxial strain on the magnitude and retention of the ferroelectric field effect in high quality PbZr0.3Ti0.7O3 (PZT)/3.8–4.3 nm Sm0.5Nd0.5NiO3 (SNNO) heterostructures grown on (001) LaAlO3 (LAO) and SrTiO3 (STO) substrates. For SNNO on LAO, which exhibits a first-order metal-insulator transition (MIT), switching the polarization of PZT induces a 10K shift in the transition temperature TMI, with a maximum resistance change between the on and off states of ΔR = Ron ~75%. In sharp contrast, only up to 5% resistance change has been …
Strategies For Increasing The Néel Temperature Of Magnetoelectric Fe2Teo6, Sai Mu, Kirill D. Belashchenko
Strategies For Increasing The Néel Temperature Of Magnetoelectric Fe2Teo6, Sai Mu, Kirill D. Belashchenko
Department of Physics and Astronomy: Faculty Publications
Ways to increase the Néel temperature TN in the magnetoelectric Fe2TeO6 antiferromagnet are explored with the help of first-principles calculations. Substitution of larger ions like Zr or Hf for tellurium increases the superexchange angles. The compensating O vacancies tend to form bound complexes with Zr dopants, which do not degrade the electronic band gap. TN is estimated to increase by 15% at 12.5% Te → Zr substitution with such compensation. Substitution of N for O is favorable due to the decreased charge-transfer gap. The overall effect for N3− substitution compensated by O vacancies …
Multiferroic Tunnel Junctions And Ferroelectric Control Of Magnetic State At Interface, Y. W. Yin, M. Raju, W. J. Hu, John D. Burton, Y.-M. Kim, A. Y. Borisevich, S. J. Pennycook, S. M. Yang, T. W. Noh, Alexei Gruverman, X. G. Li, Z. D. Zhang, Evgeny Y. Tsymbal, Qi Li
Multiferroic Tunnel Junctions And Ferroelectric Control Of Magnetic State At Interface, Y. W. Yin, M. Raju, W. J. Hu, John D. Burton, Y.-M. Kim, A. Y. Borisevich, S. J. Pennycook, S. M. Yang, T. W. Noh, Alexei Gruverman, X. G. Li, Z. D. Zhang, Evgeny Y. Tsymbal, Qi Li
Alexei Gruverman Publications
As semiconductor devices reach ever smaller dimensions, the challenge of power dissipation and quantum effect place a serious limit on the future device scaling. Recently, a multiferroic tunnel junction (MFTJ) with a ferroelectric barrier sandwiched between two ferromagnetic electrodes has drawn enormous interest due to its potential applications not only in multi-level data storage but also in electric field controlled spintronics and nanoferronics. Here, we present our investigations on four-level resistance states, giant tunneling electroresistance (TER) due to interfacial magnetoelectric coupling, and ferroelectric control of spin polarized tunneling in MFTJs. Coexistence of large tunneling magnetoresistance and TER has been observed …
Electrostatic Charge On Flying Hummingbirds And Its Potential Role In Pollination, Marc Badger, Victor Manuel Ortega-Jimenez, Lisa Von Ribenau, Ashley Smiley, Robert Dudley, Alexei Gruverman , Editor
Electrostatic Charge On Flying Hummingbirds And Its Potential Role In Pollination, Marc Badger, Victor Manuel Ortega-Jimenez, Lisa Von Ribenau, Ashley Smiley, Robert Dudley, Alexei Gruverman , Editor
Alexei Gruverman Publications
Electrostatic phenomena are known to enhance both wind- and insect-mediated pollination, but have not yet been described for nectar-feeding vertebrates. Here we demonstrate that wild Anna's Hummingbirds (Calypte anna) can carry positive charges up to 800 pC while in flight (mean ± s.d.: 66 ± 129 pC). Triboelectric charging obtained by rubbing an isolated hummingbird wing against various plant structures generated charges up to 700 pC. A metal hummingbird model charged to 400 pC induced bending of floral stamens in four plants (Nicotiana, Hemerocallis, Penstemon, and Aloe spp.), and also attracted falling Lycopodium spores at distances of < 2 mm. Electrostatic forces may therefore influence pollen transfer onto nectar-feeding birds.
Magnetic Soft X-Ray Tomography Of Magnetic Swiss Roll Architectures, Robert Streubel, F. Kronast, P. Fischer, O. G. Schmidt, D. Makarov
Magnetic Soft X-Ray Tomography Of Magnetic Swiss Roll Architectures, Robert Streubel, F. Kronast, P. Fischer, O. G. Schmidt, D. Makarov
Robert Streubel Papers
A further increase in performance of state-of-the-art spin-electronics can be achieved by either miniaturizing its functional components or harnessing the third dimension. The first route, however, faces physical limitations as properties of nanostructures and their response to external stimuli can drastically change in reduced dimensions. An alternative way is to go from planar 2D structures to 3D architectures [1]. Such 3D functional elements can be obtained for example by rolling up initially planar strained thin films into Swiss roll like objects with multiple windings (Fig. 1a). A major advantage of this technology platform is the possibility to fabricate compact multifunctional …
Magnetization Pumping And Dynamics In A Dzyaloshinskii-Moriya Magnet, Alexey Kovalev, Utkan Güngördü
Magnetization Pumping And Dynamics In A Dzyaloshinskii-Moriya Magnet, Alexey Kovalev, Utkan Güngördü
Department of Physics and Astronomy: Faculty Publications
We formulate a phenomenological description of thin ferromagnetic layers with inversion asymmetry where the single-domain magnetic dynamics experiences magnon current-induced torques and leads to magnon-motive forces. We first construct a phenomenological theory based on irreversible thermodynamics, taking into account the symmetries of the system. Furthermore, we confirm that these effects originate from Dzyaloshinskii-Moriya interactions from the analysis based on the stochastic Landau-Lifshitz-Gilbert equation. Our phenomenological results generalize to a general form of Dzyaloshinskii-Moriya interactions and to other systems, such as pyrochlore crystals and chiral magnets. Possible applications include spin current generation, magnetization reversal and magnonic cooling.