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Faculty Publications, Department of Physics and Astronomy

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Full-Text Articles in Physics

Generalized Magnetoelectronic Circuit Theory And Spin Relaxation At Interfaces In Magnetic Multilayers, G. G. Baez Flores, Alexey Kovalev, Mark Van Schilfgaarde, K. D. Belashchenko Jun 2020

Generalized Magnetoelectronic Circuit Theory And Spin Relaxation At Interfaces In Magnetic Multilayers, G. G. Baez Flores, Alexey Kovalev, Mark Van Schilfgaarde, K. D. Belashchenko

Faculty Publications, Department of Physics and Astronomy

Spin transport at metallic interfaces is an essential ingredient of various spintronic device concepts, such as giant magnetoresistance, spin-transfer torque, and spin pumping. Spin-orbit coupling plays an important role in many such devices. In particular, spin current is partially absorbed at the interface due to spin-orbit coupling. We develop a general magnetoelectronic circuit theory and generalize the concept of spin-mixing conductance, accounting for various mechanisms responsible for spin-flip scattering. For the special case when exchange interactions dominate, we give a simple expression for the spin-mixing conductance in terms of the contributions responsible for spin relaxation (i.e., spin memory loss ...


Interfacial Contributions To Spin-Orbit Torque And Magnetoresistance In Ferromagnet/Heavy-Metal Bilayers, Kirill Belashchenko, Alexey Kovalev, Mark Van Schilfgaarde Jan 2020

Interfacial Contributions To Spin-Orbit Torque And Magnetoresistance In Ferromagnet/Heavy-Metal Bilayers, Kirill Belashchenko, Alexey Kovalev, Mark Van Schilfgaarde

Faculty Publications, Department of Physics and Astronomy

The thickness dependence of spin-orbit torque and magnetoresistance in ferromagnet/heavy-metal bilayers is studied using the first-principles nonequilibrium Green’s function formalism combined with the Anderson disorder model. A systematic expansion in orthogonal vector spherical harmonics is used for the angular dependence of the torque. The dampinglike torque in Co/Pt and Co/Au bilayers can be described as a sum of the spin-Hall contribution, which increases with thickness in agreement with the spin-diffusion model, and a comparable interfacial contribution. The magnetoconductance in the plane perpendicular to the current in Co/Pt bilayers is of the order of a conductance ...


Intrinsic Spin Nernst Effect Of Magnons In A Noncollinear Antiferromagnet, Bo Li, Shane Sandhoefner, Alexey Kovalev Jan 2020

Intrinsic Spin Nernst Effect Of Magnons In A Noncollinear Antiferromagnet, Bo Li, Shane Sandhoefner, Alexey Kovalev

Faculty Publications, Department of Physics and Astronomy

We investigate the intrinsic magnon spin current in a noncollinear antiferromagnetic insulator. We introduce a definition of the magnon spin current in a noncollinear antiferromagnet and find that it is in general nonconserved, but for certain symmetries and spin polarizations the averaged effect of nonconserving terms can vanish. We formulate a general linear response theory for magnons in noncollinear antiferromagnets subject to a temperature gradient and analyze the effect of symmetries on the response tensor. We apply this theory to single-layer potassium iron jarosite KFe3(OH)6(SO4)2 and predict a measurable spin current response.


Magnonic Analog Of The Edelstein Effect In Antiferromagnetic Insulators, Bo Li, Alexander Mook, Aldo Raeliarijaona, Alexey Kovalev Jan 2020

Magnonic Analog Of The Edelstein Effect In Antiferromagnetic Insulators, Bo Li, Alexander Mook, Aldo Raeliarijaona, Alexey Kovalev

Faculty Publications, Department of Physics and Astronomy

We investigate the nonequilibrium spin polarization due to a temperature gradient in antiferromagnetic insulators, which is the magnonic analog of the inverse spin-galvanic effect of electrons. We derive a linear-response theory of a temperature-gradient-induced spin polarization for collinear and noncollinear antiferromagnets, which comprises both extrinsic and intrinsic contributions. We apply our theory to several noncentrosymmetric antiferromagnetic insulators, i.e., to a one-dimensional antiferromagnetic spin chain, a single layer of kagome noncollinear antiferromagnet,e.g.,KFe3(OH)6(SO4)2,and a noncollinear breathing pyrochlore antiferromagnet, e.g., LiGaCr4O8. The shapes of our numerically evaluated response tensors agree with those implied ...


Testing Quantum Coherence In Stochastic Electrodynamics With Squeezed Schrödinger Cat States, Wayne Cheng-Wei Huang, Herman Batelaan Apr 2019

Testing Quantum Coherence In Stochastic Electrodynamics With Squeezed Schrödinger Cat States, Wayne Cheng-Wei Huang, Herman Batelaan

Faculty Publications, Department of Physics and Astronomy

The interference pattern in electron double-slit diffraction is a hallmark of quantum mechanics. A long-standing question for stochastic electrodynamics (SED) is whether or not it is capable of reproducing such effects, as interference is a manifestation of quantum coherence. In this study, we used excited harmonic oscillators to directly test this quantum feature in SED. We used two counter-propagating dichromatic laser pulses to promote a ground-state harmonic oscillator to a squeezed Schrödinger cat state. Upon recombination of the two well-separated wavepackets, an interference pattern emerges in the quantum probability distribution but is absent in the SED probability distribution. We thus ...


Valley-Dependent Lorentz Force And Aharonov-Bohm Phase In Strained Graphene P-N Junction, Sanjay Prabhakar, Rabindra Nepal, Roderick Melnik, Alexey Kovalev Mar 2019

Valley-Dependent Lorentz Force And Aharonov-Bohm Phase In Strained Graphene P-N Junction, Sanjay Prabhakar, Rabindra Nepal, Roderick Melnik, Alexey Kovalev

Faculty Publications, Department of Physics and Astronomy

Veselago lens focusing in graphene p−n junction is promising for realizations of new generation electron optics devices. However, the effect of the strain-induced Aharonov-Bohm interference in a p−n junction has not been discussed before. We provide an experimentally feasible setup based on the Veselago lens in which the presence of strain can result in both the valley-dependent Lorentz force and Aharonov-Bohm interference. In particular, by employing the Green's function and tight-binding methods, we study the strain induced by dislocations and line defects in a p−n junction and show how the resulting Aharonov-Bohm phase and interference can ...


Systems And Methods For Scalable Perovskite Device Fabrication, Jinsong Huang, Qingfeng Dong, Yuchuan Shao Jan 2019

Systems And Methods For Scalable Perovskite Device Fabrication, Jinsong Huang, Qingfeng Dong, Yuchuan Shao

Faculty Publications, Department of Physics and Astronomy

Continuous processes for fabricating a perovskite device are described that include forming a perovskite layer or film on a substrate using a linear deposition device , and optionally using a conductive tape lamination process to form an anode or a cathode layer on the perovskite device .


Magnetoelectric Control Of Topological Phases In Graphene, Hiroyuki Takenaka, Shane Sandhoefner, Alexey Kovalev, Evgeny Tsymbal Jan 2019

Magnetoelectric Control Of Topological Phases In Graphene, Hiroyuki Takenaka, Shane Sandhoefner, Alexey Kovalev, Evgeny Tsymbal

Faculty Publications, Department of Physics and Astronomy

Topological antiferromagnetic (AFM) spintronics is an emerging field of research, which involves the topological electronic states coupled to the AFM order parameter known as the Néel vector. The control of these states is envisioned through manipulation of the Néel vector by spin-orbit torques driven by electric currents. Here we propose a different approach favorable for low-power AFM spintronics, where the control of the topological states in a two-dimensional material, such as graphene, is performed via the proximity effect by the voltage induced switching of the Néel vector in an adjacent magnetoelectric AFM insulator, such as chromia. Mediated by the symmetry ...


Duality And Free Energy Analyticity Bounds For Few-Body Ising Models With Extensive Homology Rank, Yi Jiang, Ilya Dumer, Alexey Kovalev, Leonid Pryadko Jan 2019

Duality And Free Energy Analyticity Bounds For Few-Body Ising Models With Extensive Homology Rank, Yi Jiang, Ilya Dumer, Alexey Kovalev, Leonid Pryadko

Faculty Publications, Department of Physics and Astronomy

We consider pairs of few-body Ising models where each spin enters a bounded number of interaction terms (bonds) such that each model can be obtained from the dual of the other after freezing k spins on large-degree sites. Such a pair of Ising models can be interpreted as a two-chain complex with k being the rank of the first homology group. Our focus is on the case where k is extensive, that is, scales linearly with the number of bonds n. Flipping any of these additional spins introduces a homologically nontrivial defect (generalized domain wall). In the presence of bond ...


Boundary Twists, Instabilities, And Creation Of Skyrmions And Antiskyrmions, Aldo Raeliarijaona, Rabindra Nepal, Alexey Kovalev Dec 2018

Boundary Twists, Instabilities, And Creation Of Skyrmions And Antiskyrmions, Aldo Raeliarijaona, Rabindra Nepal, Alexey Kovalev

Faculty Publications, Department of Physics and Astronomy

We formulate and study the general boundary conditions dictating the magnetization profile in the vicinity of an interface between magnets with dissimilar properties. Boundary twists in the vicinity of an edge due to Dzyaloshinskii-Moriya interactions have been first discussed by Wilson et al. [Phys. Rev. B 88, 214420 (2013)] and by Rohart and Thiaville [Phys. Rev. B 88, 184422 (2013)]. We show that in general case the boundary conditions lead to the magnetization profile corresponding to the Néel, Bloch, or intermediate twist. We explore how such twists can be utilized for creation of skyrmions and antiskyrmions, e.g., in a ...


First-Principles Calculation Of The Spin-Orbit Torques In A Co/Pt Bilayer, K. D. Belashchenko, Alexey A. Kovalev, M. Van Schilfgaarde Oct 2018

First-Principles Calculation Of The Spin-Orbit Torques In A Co/Pt Bilayer, K. D. Belashchenko, Alexey A. Kovalev, M. Van Schilfgaarde

Faculty Publications, Department of Physics and Astronomy

The spin-orbit torque in a disordered Co/Pt bilayer is calculated using a first-principles nonequilibrium Green's function formalism. The torque is formally split in the Fermi-sea and Fermi-surface contributions. The Fermi-sea term is important at low temperatures, but the Fermi-surface term dominates at room temperature. In addition to the usual damping-like and field-like terms, the odd torque contains a sizeable planar Hall-like term (m . E)m x (z x m) which contributes to damping. While the torques that contribute to damping are almost entirely due to spin-orbit coupling on the Pt atoms, the field-like torque does not require it.


Probing Tunneling Spin Injection Into Graphene Via Bias Dependence, Tiancong Zhu, Simranjeet Singh, Jyoti Katoch, Hua Wen, Kirill Belashchenko, Igor Zutic, Roland K. Kawakami Aug 2018

Probing Tunneling Spin Injection Into Graphene Via Bias Dependence, Tiancong Zhu, Simranjeet Singh, Jyoti Katoch, Hua Wen, Kirill Belashchenko, Igor Zutic, Roland K. Kawakami

Faculty Publications, Department of Physics and Astronomy

The bias dependence of spin injection in graphene lateral spin valves is systematically studied to determine the factors affecting the tunneling spin injection efficiency. Three types of junctions are investigated, including MgO and hexagonal boron nitride (hBN) tunnel barriers and direct contacts. A dc bias current applied to the injector electrode induces a strong nonlinear bias dependence of the nonlocal spin signal for both MgO and hBN tunnel barriers. Furthermore, this signal reverses its sign at a negative dc bias for both kinds of tunnel barriers. The analysis of the bias dependence for injector electrodes with a wide range of ...


Numerical And Analytical Bounds On Threshold Error Rates For Hypergraph-Product Codes, Alexey Kovalev, Sanjay Prabhakar, Ilya Dumer, Leonid P. Pryadko Jun 2018

Numerical And Analytical Bounds On Threshold Error Rates For Hypergraph-Product Codes, Alexey Kovalev, Sanjay Prabhakar, Ilya Dumer, Leonid P. Pryadko

Faculty Publications, Department of Physics and Astronomy

We study analytically and numerically decoding properties of finite-rate hypergraph-product quantum low density parity-check codes obtained from random (3,4)-regular Gallager codes, with a simple model of independent X and Z errors. Several nontrivial lower and upper bounds for the decodable region are constructed analytically by analyzing the properties of the homological difference, equal minus the logarithm of the maximum-likelihood decoding probability for a given syndrome. Numerical results include an upper bound for the decodable region from specific heat calculations in associated Ising models and a minimum-weight decoding threshold of approximately 7%.


Chiral Topological Insulator Of Magnons, Bo Li, Alexey Kovalev May 2018

Chiral Topological Insulator Of Magnons, Bo Li, Alexey Kovalev

Faculty Publications, Department of Physics and Astronomy

We propose a magnon realization of 3D topological insulator in the AIII (chiral symmetry) topological class. The topological magnon gap opens due to the presence of Dzyaloshinskii-Moriya interactions. The existence of the topological invariant is established by calculating the bulk winding number of the system. Within our model, the surface magnon Dirac cone is protected by the sublattice chiral symmetry. By analyzing the magnon surface modes, we confirm that the backscattering is prohibited. By weakly breaking the chiral symmetry, we observe the magnon Hall response on the surface due to opening of the gap. Finally, we show that by changing ...


Proximitized Materials, Igor Žutić, Alex Matos-Abiague, Benedikt Scharf, Hanan Dery, Kirill Belashchenko May 2018

Proximitized Materials, Igor Žutić, Alex Matos-Abiague, Benedikt Scharf, Hanan Dery, Kirill Belashchenko

Faculty Publications, Department of Physics and Astronomy

Advances in scaling down heterostructures and having an improved interface quality together with atomically thin two-dimensional materials suggest a novel approach to systematically design materials. A given material can be transformed through proximity effects whereby it acquires properties of its neighbors, for example, becoming superconducting, magnetic, topologically nontrivial, or with an enhanced spin-orbit coupling. Such proximity effects not only complement the conventional methods of designing materials by doping or functionalization but can also overcome their various limitations. In proximitized materials it is possible to realize properties that are not present in any constituent region of the considered heterostructure. While the ...


Origin Of Spin Reorientation Transitions In Antiferromagnetic Mnpt-Based Alloys, P.-H. Chang, I. A. Zhuravlev, K. D. Belashchenko Apr 2018

Origin Of Spin Reorientation Transitions In Antiferromagnetic Mnpt-Based Alloys, P.-H. Chang, I. A. Zhuravlev, K. D. Belashchenko

Faculty Publications, Department of Physics and Astronomy

Antiferromagnetic MnPt exhibits a spin reorientation transition (SRT) as a function of temperature, and off-stoichiometric Mn-Pt alloys also display SRTs as a function of concentration. The magnetocrystalline anisotropy in these alloys is studied using first-principles calculations based on the coherent potential approximation and the disordered local moment method. The anisotropy is fairly small and sensitive to the variations in composition and temperature due to the cancellation of large contributions from different parts of the Brillouin zone. Concentration and temperature-driven SRTs are found in reasonable agreement with experimental data. Contributions from specific band-structure features are identified and used to explain the ...


Magnetic Skyrmion Bubble Motion Driven By Surface Acoustic Waves, Rabindra Nepal, Utkan Güngördü, Alexey Kovalev Jan 2018

Magnetic Skyrmion Bubble Motion Driven By Surface Acoustic Waves, Rabindra Nepal, Utkan Güngördü, Alexey Kovalev

Faculty Publications, Department of Physics and Astronomy

We study the dynamical control of a magnetic skyrmion bubble by using counter-propagating surface acoustic waves (SAWs) in a ferromagnet. First, we determine the bubble mass and derive the force due to SAWs acting on a magnetic bubble using Thiele's method. The force that pushes the bubble is proportional to the strain gradient for the major strain component. We then study the dynamical pinning and motion of magnetic bubbles by SAWs in a nanowire. In a disk geometry, we propose a SAWs-driven skyrmion bubble oscillator with two resonant frequencies.


Stabilization And Control Of Majorana Bound States With Elongated Skyrmions, Utkan Güngördü, Shane Sandhoefner, Alexey Kovalev Jan 2018

Stabilization And Control Of Majorana Bound States With Elongated Skyrmions, Utkan Güngördü, Shane Sandhoefner, Alexey Kovalev

Faculty Publications, Department of Physics and Astronomy

We show that elongated magnetic skyrmions can host Majorana bound states in a proximity-coupled two-dimensional electron gas sandwiched between a chiral magnet and an s-wave superconductor. Our proposal requires stable skyrmions with unit topological charge, which can be realized in a wide range of multilayer magnets, and it allows quantum information transfer by using standard methods in spintronics via skyrmion motion. We also show how braiding operations can be realized in our proposal.


Spin Hall And Nernst Effects Of Weyl Magnons, Vladimir Zyuzin, Alexey Kovalev Jan 2018

Spin Hall And Nernst Effects Of Weyl Magnons, Vladimir Zyuzin, Alexey Kovalev

Faculty Publications, Department of Physics and Astronomy

In this paper, we present a simple model of a three-dimensional insulating magnetic structure which represents a magnonic analog of the layered electronic system described by A. A. Burkov and L. Balents [Phys. Rev. Lett. 107, 127205 (2011)]. In particular, our model realizes Weyl magnons as well as surface states with a Dirac spectrum. In this model, the Dzyaloshinskii-Moriya interaction is responsible for the separation of opposite Weyl points in momentum space. We calculate the intrinsic (due to the Berry curvature) transport properties of Weyl and so-called anomalous Hall effect magnons. The results are compared with fermionic analogs.


Magneto-Electric Logic Devices Using Semiconductor Channel With Large Spin-Orbit Coupling (U.S. Patent Application), Dmitri E. Nikonov, Christian Binek, Xia Hong, Jonathan P. Bird, Kang L. Wang, Peter Dowben Jan 2018

Magneto-Electric Logic Devices Using Semiconductor Channel With Large Spin-Orbit Coupling (U.S. Patent Application), Dmitri E. Nikonov, Christian Binek, Xia Hong, Jonathan P. Bird, Kang L. Wang, Peter Dowben

Faculty Publications, Department of Physics and Astronomy

Antiferromagnetic magneto-electric spin-orbit read (AF-SOR) logic devices are presented. The devices include a voltage-controlled magnetoelectric (ME) layer that switches polarization in response to an electric field from the applied voltage and a narrow channel conductor of a spin-orbit coupling (SOC) material on the ME layer. One or more sources and one or more drains, each optionally formed of ferromagnetic material, are provided on the SOC material.


Laser-Induced Electron Emission From Au Nanowires: A Probe For Orthogonal Polarizations, Eric R. Jones, Wayne Cheng-Wei Huang, Gobind Basnet, Bret N. Flanders, Herman Batelaan Jan 2018

Laser-Induced Electron Emission From Au Nanowires: A Probe For Orthogonal Polarizations, Eric R. Jones, Wayne Cheng-Wei Huang, Gobind Basnet, Bret N. Flanders, Herman Batelaan

Faculty Publications, Department of Physics and Astronomy

Photoelectron field emission, induced by femtosecond laser pulses focused on metallic nanotips, provides spatially coherent and temporally short electron pulses. The properties of the photoelectron yield give insight into both the material properties of the nanostructure and the exciting laser focus. Ultralong nanoribbons, grown as a single crystal attached to a metallic taper, are sources of electron field emission that have not yet been characterized. In this report, photoemission from gold nanoribbon samples is studied and compared to emission from tungsten and gold tips. We observe that the emission from sharp tips generally depends on one transverse component of the ...


Phase Stability, Ordering Tendencies, And Magnetism In Single-Phase Fcc Au-Fe Nanoalloys, I. A. Zhuravlev, S. V. Barabash, J. M. An, K. D. Belashchenko Oct 2017

Phase Stability, Ordering Tendencies, And Magnetism In Single-Phase Fcc Au-Fe Nanoalloys, I. A. Zhuravlev, S. V. Barabash, J. M. An, K. D. Belashchenko

Faculty Publications, Department of Physics and Astronomy

Bulk Au-Fe alloys separate into Au-based fcc and Fe-based bcc phases, but L10 and L12 orderings were reported in single-phase Au-Fe nanoparticles. Motivated by these observations, we study the structural and ordering energetics in this alloy by combining density functional theory (DFT) calculations with effective Hamiltonian techniques: a cluster expansion with structural filters, and the configuration-dependent lattice deformation model. The phase separation tendency in Au-Fe persists even if the fcc-bcc decomposition is suppressed. The relative stability of disordered bcc and fcc phases observed in nanoparticles is reproduced, but the fully ordered L10 AuFe, L12 Au3Fe, and L12 AuFe3 structures are ...


Distance Verification For Classical And Quantum Ldpc Codes, Ilya Dumer, Alexey Kovalev, Leonid P. Pryadko Jul 2017

Distance Verification For Classical And Quantum Ldpc Codes, Ilya Dumer, Alexey Kovalev, Leonid P. Pryadko

Faculty Publications, Department of Physics and Astronomy

The techniques of distance verification known for general linear codes are first applied to the quantum stabilizer codes. Then, these techniques are considered for classical and quantum (stabilizer) low-density-parity-check (LDPC) codes. New complexity bounds for distance verification with provable performance are derived using the average weight spectra of the ensembles of LDPC codes. These bounds are expressed in terms of the erasure-correcting capacity of the corresponding ensemble. We also present a new irreducible-cluster technique that can be applied to any LDPC code and takes advantage of parity-checks’ sparsity for both the classical and quantum LDPC codes. This technique reduces complexity ...


Reversible Spin Texture In Ferroelectric Hfo2, L. L. Tao, Tula R. Paudel, Alexey Kovalev, Evgeny Tsymbal Jun 2017

Reversible Spin Texture In Ferroelectric Hfo2, L. L. Tao, Tula R. Paudel, Alexey Kovalev, Evgeny Tsymbal

Faculty Publications, Department of Physics and Astronomy

Spin-orbit coupling effects occurring in noncentrosymmetric materials are known to be responsible for nontrivial spin configurations and a number of emergent physical phenomena. Ferroelectric materials may be especially interesting in this regard due to reversible spontaneous polarization making possible a nonvolatile electrical control of the spin degrees of freedom. Here, we explore a technologically relevant oxide material, HfO2, which has been shown to exhibit robust ferroelectricity in a noncentrosymmetric orthorhombic phase. Using theoretical modelling based on density-functional theory, we investigate the spin-dependent electronic structure of the ferroelectric HfO2 and demonstrate the appearance of chiral spin textures driven by spin-orbit coupling ...


Pumping Of Magnons In A Dzyaloshinskii-Moriya Ferromagnet, Alexey Kovalev, Vladimir Zyuzin, Bo Li Apr 2017

Pumping Of Magnons In A Dzyaloshinskii-Moriya Ferromagnet, Alexey Kovalev, Vladimir Zyuzin, Bo Li

Faculty Publications, Department of Physics and Astronomy

We formulate a microscopic linear response theory of magnon pumping applicable to multiple-magnonic-band uniform ferromagnets with Dzyaloshinskii-Moriya interactions. From the linear response theory, we identify the extrinsic and intrinsic contributions where the latter is expressed via the Berry curvature of magnonic bands. We observe that in the presence of a time-dependent magnetization Dzyaloshinskii-Moriya interactions can act as fictitious electric fields acting on magnons. We study various current responses to this fictitious field and analyze the role of Berry curvature. In particular, we obtain an analog of the Hall-like response in systems with nontrivial Berry curvature of magnon bands. After identifying ...


Two-Color Multiphoton Emission From Nanotips, Wayne Cheng-Wei Huang, Maria Becker, Joshua Beck, Herman Batelaan Feb 2017

Two-Color Multiphoton Emission From Nanotips, Wayne Cheng-Wei Huang, Maria Becker, Joshua Beck, Herman Batelaan

Faculty Publications, Department of Physics and Astronomy

Two-color multiphoton emission from polycrystalline tungsten nanotips has been demonstrated using two-color laser fields. The two-color photoemission is assisted by a three-photon multicolor quantum channel, which leads to a twofold increase in quantum efficiency. Weak-field control of two- color multiphoton emission was achieved by changing the efficiency of the quantum channel with pulse delay. The result of this study complements two-color tunneling photoemission in strong fields, and has potential applications for nanowire-based photonic devices. Moreover, the demonstrated two-color multiphoton emission may be important for realizing ultrafast spin-polarized electron sources via optically injected spin current.


Structure Evolution And Multiferroic Properties In Cobalt Doped Bi4Ndti3Fe1-XCoXO15- Bi3Ndti2Fe1-XCoxo12-Δ Intergrowth Aurivillius Compounds, D. L. Zhang, W. C. Huang, Z. W. Chen, W. B. Zhao, L. Feng, M. Li, Y. W. Yin, S. N. Dong, X. G. Li Jan 2017

Structure Evolution And Multiferroic Properties In Cobalt Doped Bi4Ndti3Fe1-XCoXO15- Bi3Ndti2Fe1-XCoxo12-Δ Intergrowth Aurivillius Compounds, D. L. Zhang, W. C. Huang, Z. W. Chen, W. B. Zhao, L. Feng, M. Li, Y. W. Yin, S. N. Dong, X. G. Li

Faculty Publications, Department of Physics and Astronomy

Here, we report the structure evolution, magnetic and ferroelectric properties in Co-doped 4- and 3-layered intergrowth Aurivillius compounds Bi4NdTi3Fe1-x CoxO15-Bi3NdTi2Fe1-xCoxO12-δ. The compounds suffer a structure evolution from the parent 4-layered phase (Bi4NdTi3FeO15) to 3-layered phase (Bi3NdTi2CoO12-δ) with increasing cobalt doping level from 0 to 1. Meanwhile the remanent magnetization and polarization show opposite variation tendencies against the doping level, and the sample with x = 0.3 has the ...


Dualism Between Optical And Difference Parametric Amplification, Wayne Cheng-Wei Huang, Herman Batelaan Jan 2017

Dualism Between Optical And Difference Parametric Amplification, Wayne Cheng-Wei Huang, Herman Batelaan

Faculty Publications, Department of Physics and Astronomy

Breaking the symmetry in a coupled wave system can result in unusual amplification behavior. In the case of difference parametric amplification the resonant pump frequency is equal to the difference, instead of the sum, frequency of the normal modes. We show that sign reversal in the symmetry relation of parametric coupling give rise to difference parametric amplification as a dual of optical parametric amplification. For optical systems, our result can potentially be used for efficient XUV amplification.


Magnon Spin Nernst Effect In Antiferromagnets, Vladimir Zyuzin, Alexey Kovalev Nov 2016

Magnon Spin Nernst Effect In Antiferromagnets, Vladimir Zyuzin, Alexey Kovalev

Faculty Publications, Department of Physics and Astronomy

We predict that a temperature gradient can induce a magnon-mediated spin Hall response in an antiferromagnet with nontrivial magnon Berry curvature. We develop a linear response theory which gives a general condition for a Hall current to be well defined, even when the thermal Hall response is forbidden by symmetry. We apply our theory to a honeycomb lattice antiferromagnet and discuss a role of magnon edge states in a finite geometry.


Theory Of Spin Loss At Metallic Interfaces, Kirill D. Belashchenko, Alexey Kovalev, Mark Van Schilfgaarde Nov 2016

Theory Of Spin Loss At Metallic Interfaces, Kirill D. Belashchenko, Alexey Kovalev, Mark Van Schilfgaarde

Faculty Publications, Department of Physics and Astronomy

Interfacial spin-flip scattering plays an important role in magnetoelectronic devices. Spin loss at metallic interfaces is usually quantified by matching the magnetoresistance data for multilayers to the Valet-Fert model, while treating each interface as a fictitious bulk layer whose thickness is δ times the spin-diffusion length. By employing the properly generalized circuit theory and the scattering matrix approaches, we derive the relation of the parameter δ to the spin-flip transmission and reflection probabilities at an individual interface. It is found that δ is proportional to the square root of the probability of spin-flip scattering. We calculate the spin-flip scattering probabilities ...