Domain wall magnetoresistance in BiFeO3 thin films measured by scanning probe microscopy
Domingo, N.; Farokhipoor, S.; Santiso, J.; Noheda, B.; Catalan, G.
2017-08-01
We measure the magnetotransport properties of individual 71° domain walls in multiferroic BiFeO3 by means of conductive—atomic force microscopy (C-AFM) in the presence of magnetic fields up to one Tesla. The results suggest anisotropic magnetoresistance at room temperature, with the sign of the magnetoresistance depending on the relative orientation between the magnetic field and the domain wall plane. A consequence of this finding is that macroscopically averaged magnetoresistance measurements for domain wall bunches are likely to underestimate the magnetoresistance of each individual domain wall.
Hu, Bo; He, Wei; Ye, Jun; Tang, Jin; Zhang, Yong-Sheng; Ahmad, Syed Sheraz; Zhang, Xiang-Qun; Cheng, Zhao-Hua
2015-09-15
It is challenging to determine domain wall pinning energy and magnetic anisotropy since both coherent rotation and domain wall displacement coexist during magnetization switching process. Here, angular dependence anisotropic magnetoresistance (AMR) measurements at different magnetic fields were employed to determine magnetic anisotropy constants and domain wall pinning energy of Fe/MgO(001) ultrathin film. The AMR curves at magnetic fields which are high enough to ensure the coherent rotation of magnetization indicate a smooth behavior without hysteresis between clockwise (CW) and counter-clockwise (CCW) rotations. By analyzing magnetic torque, the magnetic anisotropy constants can be obtained. On the other hand, the AMR curves at low fields show abrupt transitions with hysteresis between CW and CCW rotations, suggesting the presence of multi-domain structures. The domain wall pinning energy can be obtained by analyzing different behaviors of AMR. Our work suggests that AMR measurements can be employed to figure out precisely the contributions of magnetic anisotropy and domain wall pinning energy, which is still a critical issue for spintronics.
Energy Technology Data Exchange (ETDEWEB)
Xiang Gang; Zhang Xi, E-mail: gxiang@scu.edu.cn [Department of Physics, Sichuan University Chengdu, Sichuan 610064 (China)
2011-01-01
Symmetry of the longitudinal mangetoresistance (MR) of ferromagnetic thin films with perpendicular magnetic anisotropy (PMA) in the presence of multiple domain walls (DWs) has been studied. Based on exact solutions, schematic representations of electric fields and MR have been established considering anomalous Hall effect and the effect from the eddy currents in the proximity of domain walls in the ferromagnetic samples with PMA. Symmetry analysis shows that MR with single DW in opposite sweeps is antisymmetric with respect to H = 0, MR with two or 2n (n is integer, n >0) evenly distributed DWs is symmetric, and MR with the three or 2n+1 (n is integer, n >0) evenly distributed DWs is antisymmetric.
Halyo, Edi
2009-01-01
We describe domain walls that live on $A_2$ and $A_3$ singularities. The walls are BPS if the singularity is resolved and non--BPS if it is deformed and fibered. We show that these domain walls may interpolate between vacua that support monopoles and/or vortices.
Staggered domain wall fermions
Hoelbling, Christian
2016-01-01
We construct domain wall fermions with a staggered kernel and investigate their spectral and chiral properties numerically in the Schwinger model. In some relevant cases we see an improvement of chirality by more than an order of magnitude as compared to usual domain wall fermions. Moreover, we present first results for four-dimensional quantum chromodynamics, where we also observe significant reductions of chiral symmetry violations for staggered domain wall fermions.
Bär, O; Neuberger, H; Witzel, O; Baer, Oliver; Narayanan, Rajamani; Neuberger, Herbert; Witzel, Oliver
2007-01-01
We propose using the extra dimension separating the domain walls carrying lattice quarks of opposite handedness to gradually filter out the ultraviolet fluctuations of the gauge fields that are felt by the fermionic excitations living in the bulk. This generalization of the homogeneous domain wall construction has some theoretical features that seem nontrivial.
Axion domain wall baryogenesis
Energy Technology Data Exchange (ETDEWEB)
Daido, Ryuji; Kitajima, Naoya [Department of Physics, Tohoku University,Sendai 980-8578 (Japan); Takahashi, Fuminobu [Department of Physics, Tohoku University,Sendai 980-8578 (Japan); Kavli IPMU, TODIAS, University of Tokyo,Kashiwa 277-8583 (Japan)
2015-07-28
We propose a new scenario of baryogenesis, in which annihilation of axion domain walls generates a sizable baryon asymmetry. Successful baryogenesis is possible for a wide range of the axion mass and decay constant, m≃10{sup 8}–10{sup 13} GeV and f≃10{sup 13}–10{sup 16} GeV. Baryonic isocurvature perturbations are significantly suppressed in our model, in contrast to various spontaneous baryogenesis scenarios in the slow-roll regime. In particular, the axion domain wall baryogenesis is consistent with high-scale inflation which generates a large tensor-to-scalar ratio within the reach of future CMB B-mode experiments. We also discuss the gravitational waves produced by the domain wall annihilation and its implications for the future gravitational wave experiments.
Interactions between domain walls and spin currents
Klaui, M.; Laufenberg, M.; Backes, D.; Buhrer, W.; Rudiger, U.; Vila, L.; Vouille, C.; Faini, G.
2006-03-01
A promising novel approach for switching magnetic nanostructures is current-induced domain wall propagation (CIDP), where due to a spin torque effect, electrons transfer angular momentum to a head-to-head domain wall and thereby push it in the direction of the electron flow without any externally applied fields. This effect has been observed with a variety of techniques including MFM [1] and spin polarized scanning electron microscopy [2] to directly observe current-induced domain wall propagation in ferromagnetic nanostructures and magnetoresistance measurements to systematically probe the critical current densities as a function of the geometry [3]. The observed wall velocities and critical current densities, where wall motion sets in at room temperature, do not agree well with theoretical 0K calculations [4]. We have therefore measured the critical current densities as a function of the sample temperature. We find that the spin torque effect becomes more efficient at low temperatures, which could account for some of the observed discrepancies between the 300K experiment and the 0K simulation. [1] A. Yamaguchi et al., Phys. Rev. Lett. 92, 77205 (2004); [2] M. Klaui et al., PRL 95, 26601 (2005); [3] M. Klaui et al., PRL 94, 106601 (2005); [4] A. Thiaville et al., EPL 69, 990 (2005); G. Tatara et al., APL 86, 252509 (2005);
Dynamical domain wall and localization
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Yuta Toyozato
2016-03-01
Full Text Available Based on the previous works (Toyozato et al., 2013 [24]; Higuchi and Nojiri, 2014 [25], we investigate the localization of the fields on the dynamical domain wall, where the four-dimensional FRW universe is realized on the domain wall in the five-dimensional space–time. Especially we show that the chiral spinor can localize on the domain wall, which has not been succeeded in the past works as the seminal work in George et al. (2009 [23].
Directory of Open Access Journals (Sweden)
V. Fallahi
2012-06-01
Full Text Available The magnetoresistance of a one-dimensional electron gas in a metallic ferromagnetic nanowire containing two atomic-size domain walls has been investigated in the presence of spin-orbit interaction. The magnetoresistance is calculated in the ballistic regime, within the Landauer-Büttiker formalism. It has been demonstrated that the conductance of a magnetic nanowire with double domain walls can be controlled through the domain walls separation. Also, we have represented another alternative way that enables us to handle easily the magnetoresistance of such a system as well as its conductance by utilizing the Rashba-type spin-orbit interaction induced by the external gates.
Structure of axionic domain walls
Huang, M. C.; Sikivie, P.
1985-09-01
The structure of axionic domain walls is investigated using the low-energy effective theory of axions and pions. We derive the spatial dependence of the phases of the Peccei-Quinn scalar field and the QCD quark-antiquark condensates inside an axionic domain wall. Thence an accurate estimate of the wall surface energy density is obtained. The equations of motion for axions, photons, leptons, and baryons in the neighborhood of axionic domain walls are written down and estimates are given for the wall reflection and transmission coefficients of these particles. Finally, we discuss the energy dissipation by axionic domain walls oscillating in the early universe due to the reflection of particles in the primordial soup.
Structure of axionic domain walls
Energy Technology Data Exchange (ETDEWEB)
Huang, M.C.; Sikivie, P.
1985-09-15
The structure of axionic domain walls is investigated using the low-energy effective theory of axions and pions. We derive the spatial dependence of the phases of the Peccei-Quinn scalar field and the QCD quark-antiquark condensates inside an axionic domain wall. Thence an accurate estimate of the wall surface energy density is obtained. The equations of motion for axions, photons, leptons, and baryons in the neighborhood of axionic domain walls are written down and estimates are given for the wall reflection and transmission coefficients of these particles. Finally, we discuss the energy dissipation by axionic domain walls oscillating in the early universe due to the reflection of particles in the primordial soup.
Domain wall description of superconductivity
Brito, F A; Silva, J C M
2012-01-01
In the present work we shall address the issue of electrical conductivity in superconductors in the perspective of superconducting domain wall solutions in the realm of field theory. We take our set up made out of a dynamical complex scalar field coupled to gauge field to be responsible for superconductivity and an extra scalar real field that plays the role of superconducting domain walls. The temperature of the system is interpreted as the parameter to move type I to type II domain walls. Alternatively, this means that the domain wall surface is suffering an acceleration as one goes from one type to another. On the other hand, changing from type I to type II state means a formation of a condensate what is in perfect sense of lowering the temperature around the superconductor. One can think of this scenario as an analog of holographic scenarios where this set up is replaced by a black hole near the domain wall.
Poghosian, L E; Pogosian, Levon; Vachaspati, Tanmay
2000-01-01
We consider the Grand Unified SU(5) model with a small or vanishing cubic term in the adjoint scalar field in the potential. This gives the model an approximate or exact Z$_2$ symmetry whose breaking leads to domain walls. The simplest domain wall has the structure of a kink across which the Higgs field changes sign ($\\Phi \\to -\\Phi$) and inside which the full SU(5) is restored. The kink is shown to be perturbatively unstable for all parameters. We then construct a domain wall solution that is lighter than the kink and show it to be perturbatively stable for a range of parameters. The symmetry in the core of this domain wall is smaller than that outside. The interactions of the domain wall with magnetic monopole is discussed and it is shown that magnetic monopoles with certain internal space orientations relative to the wall pass through the domain wall. Magnetic monopoles in other relative internal space orientations are likely to be swept away on collision with the domain walls, suggesting a scenario where ...
Borie, B.; Kehlberger, A.; Wahrhusen, J.; Grimm, H.; Kläui, M.
2017-08-01
We study the key domain-wall properties in segmented nanowire loop-based structures used in domain-wall-based sensors. The two reasons for device failure, namely, distribution of the domain-wall propagation field (depinning) and the nucleation field are determined with magneto-optical Kerr effect and giant-magnetoresistance (GMR) measurements for thousands of elements to obtain significant statistics. Single layers of Ni81 Fe19 , a complete GMR stack with Co90 Fe10 /Ni81Fe19 as a free layer, and a single layer of Co90 Fe10 are deposited and industrially patterned to determine the influence of the shape anisotropy, the magnetocrystalline anisotropy, and the fabrication processes. We show that the propagation field is influenced only slightly by the geometry but significantly by material parameters. Simulations for a realistic wire shape yield a curling-mode type of magnetization configuration close to the nucleation field. Nonetheless, we find that the domain-wall nucleation fields can be described by a typical Stoner-Wohlfarth model related to the measured geometrical parameters of the wires and fitted by considering the process parameters. The GMR effect is subsequently measured in a substantial number of devices (3000) in order to accurately gauge the variation between devices. This measurement scheme reveals a corrected upper limit to the nucleation fields of the sensors that can be exploited for fast characterization of the working elements.
Semi-analytical Single-domain Modeling of Magnetoresistive Multilayer Thin Films
Oti, John O.
1997-03-01
Sub-micrometer magnetoresistive (MR) multilayer thin films show great promise as active elements of future-generation magnetic recording read heads and sensors, and non-volatile magnetic random access memory (MRAM) devices. In very small films the transition lengths of internal Neel magnetic domain walls films may become larger than the dimensions of the films, thereby rendering the films incapable of sustaining domain walls. The films then display a predominant single-domain behavior. This greatly simplifies the mathematical modeling of very small MR multilayers. Simulated size dependence properties of the MR behavior of spin-valve read heads and MRAMs, using a semi-analytical single-domain model [1,2], are presented. The model forms part of a personal computer based semi-analytical micromagnetics design tool we have developed. The program utilizes a convenient graphical windowing interface that facilitates the design and analysis of the system, and enables the 3-D rendering of the interacting films and animation of their magnetization reversals. A real-time demonstration of the program will be given as part of the presentation. [1] C. E. Johnson, J. Appl. Phys. 33, 2515 (1962). [2] J. O. Oti, J. Appl. Phys. 79, 6386 (1996).
Visualizing domain wall and reverse domain superconductivity.
Iavarone, M; Moore, S A; Fedor, J; Ciocys, S T; Karapetrov, G; Pearson, J; Novosad, V; Bader, S D
2014-08-28
In magnetically coupled, planar ferromagnet-superconductor (F/S) hybrid structures, magnetic domain walls can be used to spatially confine the superconductivity. In contrast to a superconductor in a uniform applied magnetic field, the nucleation of the superconducting order parameter in F/S structures is governed by the inhomogeneous magnetic field distribution. The interplay between the superconductivity localized at the domain walls and far from the walls leads to effects such as re-entrant superconductivity and reverse domain superconductivity with the critical temperature depending upon the location. Here we use scanning tunnelling spectroscopy to directly image the nucleation of superconductivity at the domain wall in F/S structures realized with Co-Pd multilayers and Pb thin films. Our results demonstrate that such F/S structures are attractive model systems that offer the possibility to control the strength and the location of the superconducting nucleus by applying an external magnetic field, potentially useful to guide vortices for computing application.
Domain wall description of superconductivity
Energy Technology Data Exchange (ETDEWEB)
Brito, F.A. [Departamento de Física, Universidade Federal de Campina Grande, Caixa Postal 10071, 58109-970 Campina Grande, Paraíba (Brazil); Freire, M.L.F. [Departamento de Física, Universidade Estadual da Paraíba, 58109-753 Campina Grande, Paraíba (Brazil); Mota-Silva, J.C. [Departamento de Física, Universidade Federal de Campina Grande, Caixa Postal 10071, 58109-970 Campina Grande, Paraíba (Brazil); Departamento de Física, Universidade Federal da Paraíba, Caixa Postal 5008, 58051-970 João Pessoa, Paraíba (Brazil)
2014-01-20
In the present work we shall address the issue of electrical conductivity in superconductors in the perspective of superconducting domain wall solutions in the realm of field theory. We take our set up made out of a dynamical complex scalar field coupled to gauge field to be responsible for superconductivity and an extra scalar real field that plays the role of superconducting domain walls. The temperature of the system is interpreted through the fact that the soliton following accelerating orbits is a Rindler observer experiencing a thermal bath.
Diffusion-damped domain wall dynamics
Energy Technology Data Exchange (ETDEWEB)
Varga, R; Infante, G [Inst. Phys., Fac. Sci., UPJS, Park Angelinum 9, 04154 Kosice (Slovakia); Badini-Confalonieri, G A; Vazquez, M, E-mail: rvarga@upjs.s [Instituto de Ciencia de Materiales de Madrid, CSIC, Cantoblanco, 28049, Madrid (Spain)
2010-01-01
In the given work, the influence of diffusional damping on the domain wall dynamics of heat treated FeSiBP microwires is presented. Two regions of the domain wall dynamics have been found. At low applied fields diffusion damping prevails, keeping the domain wall velocity and mobility low. At higher fields, the diffusional effects are overcomed and domain wall velocity increases steeply and so does the domain wall mobility.
Overlap/Domain-wall reweighting
Fukaya, H; Cossu, G; Hashimoto, S; Kaneko, T; Noaki, J
2013-01-01
We investigate the eigenvalues of nearly chiral lattice Dirac operators constructed with five-dimensional implementations. Allowing small violation of the Ginsparg-Wilson relation, the HMC simulation is made much faster while the eigenvalues are not significantly affected. We discuss the possibility of reweighting the gauge configurations generated with domain-wall fermions to those of exactly chiral lattice fermions.
Partial domain wall partition functions
Foda, O
2012-01-01
We consider six-vertex model configurations on a rectangular lattice with n (N) horizontal (vertical) lines, and "partial domain wall boundary conditions" defined as 1. all 2n arrows on the left and right boundaries point inwards, 2. n_u (n_l) arrows on the upper (lower) boundary, such that n_u + n_l = N - n, also point inwards, 3. all remaining n+N arrows on the upper and lower boundaries point outwards, and 4. all spin configurations on the upper and lower boundaries are summed over. To generate (n-by-N) "partial domain wall configurations", one can start from A. (N-by-N) configurations with domain wall boundary conditions and delete n_u (n_l) upper (lower) horizontal lines, or B. (2n-by-N) configurations that represent the scalar product of an n-magnon Bethe eigenstate and an n-magnon generic state on an N-site spin-1/2 chain, and delete the n lines that represent the Bethe eigenstate. The corresponding "partial domain wall partition function" is computed in construction {A} ({B}) as an N-by-N (n-by-n) det...
Static domain wall in braneworld gravity
Energy Technology Data Exchange (ETDEWEB)
Abdalla, M.C.B.; Carlesso, P.F. [UNESP, Universidade Estadual Paulista, Instituto de Fisica Teiorica, Rua Dr. Bento Teobaldo Ferraz 271, Bloco II, Barra-Funda, Caixa Postal 70532-2, Sao Paulo, SP (Brazil); Hoff da Silva, J.M. [UNESP, Universidade Estadual Paulista, Departamento de Fisica e Quimica, Guaratingueta, SP (Brazil)
2014-01-15
In this paper we consider a static domain wall inside a 3-brane. Different from the standard achievement obtained in General Relativity, the analysis performed here gives a consistency condition for the existence of static domain walls in a braneworld gravitational scenario. Also the behavior of the domain wall's gravitational field in the newtonian limit is shown. (orig.)
Selective domain wall depinning by localized Oersted fields and Joule heating
Ilgaz, Dennis; Kläui, Mathias; Heyne, Lutz; Boulle, Olivier; Zinser, Fabian; Krzyk, Stephen; Fonin, Mikhail; Rüdiger, Ulrich; Backes, Dirk; Heyderman, Laura J.
2008-09-01
Using low temperature magnetoresistance measurements, the possibility to selectively move a domain wall locally by applying current pulses through a Au nanowire adjacent to a permalloy element is studied. We find that the domain wall depinning field is drastically modified with increasing current density due to the Joule heating and the Oersted field of the current, and controlled motion due to the Oersted field without any externally applied fields is achieved. By placing the domain wall at various distances from the Au wire, we determine the range of the Joule heating and the Oersted field and both effects can be separated.
Magnetic domain wall engineering in a nanoscale permalloy junction
Wang, Junlin; Zhang, Xichao; Lu, Xianyang; Zhang, Jason; Yan, Yu; Ling, Hua; Wu, Jing; Zhou, Yan; Xu, Yongbing
2017-08-01
Nanoscale magnetic junctions provide a useful approach to act as building blocks for magnetoresistive random access memories (MRAM), where one of the key issues is to control the magnetic domain configuration. Here, we study the domain structure and the magnetic switching in the Permalloy (Fe20Ni80) nanoscale magnetic junctions with different thicknesses by using micromagnetic simulations. It is found that both the 90-° and 45-° domain walls can be formed between the junctions and the wire arms depending on the thickness of the device. The magnetic switching fields show distinct thickness dependencies with a broad peak varying from 7 nm to 22 nm depending on the junction sizes, and the large magnetic switching fields favor the stability of the MRAM operation.
Domain Wall Propagation through Spin Wave Emission
Wang, X.S.; Yan, P.; Shen, Y.H.; Bauer, G.E.W.; Wang, X.R.
2012-01-01
We theoretically study field-induced domain wall motion in an electrically insulating ferromagnet with hard- and easy-axis anisotropies. Domain walls can propagate along a dissipationless wire through spin wave emission locked into the known soliton velocity at low fields. In the presence of damping
Domain wall solutions with Abelian gauge fields
Rozowsky, J S; Wali, K C
2004-01-01
We study kink (domain wall) solutions in a model consisting of two complex scalar fields coupled to two independent Abelian gauge fields in a Lagrangian that has $U(1)\\times U(1)$ gauge plus $\\mathbb{Z}_2$ discrete symmetry. We find consistent solutions such that while the U(1) symmetries of the fields are preserved while in their respective vacua, they are broken on the domain wall. The gauge field solutions show that the domain wall is sandwiched between domains with constant magnetic fields.
Magnetic field asymmetry and high temperature magnetoresistance in single-walled carbon nanotubes
Cobden, David
2006-03-01
The length scales and scattering processes in the one-dimensional electron system in single-walled carbon nanotubes remain only partially understood. Measuring the magnetoresistance, in both linear and nonlinear response, is a way to investigate these processes. In disordered nanotubes with ballistic paths much shorter than the length, we observe magnetoresistance in the metallic regime which at low temperatures resembles the universal fluctuations and weak localization seen in higher dimensional metals. A parabolic magnetoresistance persists at room temperature, indicating a significant role for phase coherence and/or interactions at high temperatures. While the linear resistance of a two-terminal sample must be an even function of magnetic field B by Onsager's principle, the nonlinear resistance need not be. Importantly, the B-asymmetric nonlinear terms can in principle be used to infer the strength of electron-electron interactions in the sample [1]. We have therefore also measured in detail the lowest order B-asymmetric current contributions, with a focus on the B-linear term. This has apparently not been done before in any system. Consistent with general theory, at high temperatures the term is small and has a constant sign independent of Fermi energy. At low temperatures it grows and develops mesoscopic fluctuations. Although these result imply that interactions are involved in the transport, calculations specific to nanotubes are needed in order to extract interaction parameters. This work was done by the authors of Ref [2]. References: [1] E.L. Ivchenko and B. Spivak, Phys. Rev. B 66, 155404 (2002); [2] Jiang Wei, Michael Shimogawa, Zenghui Wang, Iuliana Radu, Robert Dormaier, and David H. Cobden, Phys. Rev. Lett. (Dec. 2005) (cond-mat/0506275).
Mohammed, Hanan
2016-03-01
Magnetotransport measurements were performed on multisegmented Co/Ni nanowires fabricated by template-assisted electrodeposition. Individual nanowires were isolated and electrodes patterned to study their magnetization reversal process. The magnetoresistance reversal curve of the multisegmented nanowire exhibits a step in the switching field. Micromagnetic simulations of the magnetization reversal process are in agreement with the experimental findings and attribute the step at the switching field to the pinning of a domain wall at the interface of the Co/Ni nanowire.
Electrical Transport and Magnetoresistance in Single-Wall Carbon Nanotubes Films
Directory of Open Access Journals (Sweden)
Vitaly KSENEVICH
2014-06-01
Full Text Available Electrical transport properties and magnetoresistance of single-wall carbon nanotubes (SWCNT films were investigated within temperature range (2 – 300 K and in magnetic fields up to 8 T. A crossover between metallic (dR/dT > 0 and non-metallic (dR/dT < 0 temperature dependence of the resistance as well as low-temperature saturation of the resistance in high bias regime indicated on the diminishing of role of the contact barriers between individual nanotubes essential for the charge transport in SWCNT arrays. The magnetoresistance (MR data demonstrated influence of weak localization and electron-electron interactions on charge transport properties in SWCNT films. The low-field negative MR with positive upturn was observed at low temperatures. At T > 10 K only negative MR was observed in the whole range of available magnetic fields. The negative MR can be approximated using 1D weak localization (WL model. The low temperature positive MR is induced by contribution from electron-electron interactions. DOI: http://dx.doi.org/10.5755/j01.ms.20.2.6311
Skyrmions from Instantons inside Domain Walls
Eto, M; Ohashi, K; Tong, D; Eto, Minoru; Nitta, Muneto; Ohashi, Keisuke; Tong, David
2005-01-01
Some years ago, Atiyah and Manton described a method to construct approximate Skyrmion solutions from Yang-Mills instantons. Here we present a dynamical realization of this construction using domain walls in a five-dimensional gauge theory. The non-abelian gauge symmetry is broken in each vacuum but restored in the core of the domain wall, allowing instantons to nestle inside the wall. We show that the worldvolume dynamics of the wall is given by the Skyrme model, including the four-derivative term, and the instantons appear as Skyrmions.
Domain wall magneto-Seebeck effect
Krzysteczko, Patryk; Hu, Xiukun; Liebing, Niklas; Sievers, Sibylle; Schumacher, Hans W.
2015-10-01
The interplay between charge, spin, and heat currents in magnetic nanostructures subjected to a temperature gradient has led to a variety of novel effects and promising applications studied in the fast-growing field of spin caloritronics. Here, we explore the magnetothermoelectrical properties of an individual magnetic domain wall in a permalloy nanowire. In thermal gradients of the order of few K /μ m along the long wire axis, we find a clear magneto-Seebeck signature due to the presence of a single domain wall. The observed domain wall magneto-Seebeck effect can be explained by the magnetization-dependent Seebeck coefficient of permalloy in combination with the local spin configuration of the domain wall.
Domain Wall Evolution in Phase Transforming Oxides
2015-01-14
PERFORMING ORGANIZATION NAMES AND ADDRESSES 8. PERFORMI:N’G ORGANIZATION REPORT University ofFioridaOffice ofEngineering NUMBER 339 Wei I Hall ...surveillance, navigation, tlrreat identification, target acquisition, and missile guidance. Domain wall motion, or the planar defects separating regions of...surveillance, navigation, threat identification, target acquisition, and missile guidance. Domain wall motion, or the planar defects separating regions of
Robust ferromagnetism carried by antiferromagnetic domain walls
Hirose, Hishiro T.; Yamaura, Jun-Ichi; Hiroi, Zenji
2017-02-01
Ferroic materials, such as ferromagnetic or ferroelectric materials, have been utilized as recording media for memory devices. A recent trend for downsizing, however, requires an alternative, because ferroic orders tend to become unstable for miniaturization. The domain wall nanoelectronics is a new developing direction for next-generation devices, in which atomic domain walls, rather than conventional, large domains themselves, are the active elements. Here we show that atomically thin magnetic domain walls generated in the antiferromagnetic insulator Cd2Os2O7 carry unusual ferromagnetic moments perpendicular to the wall as well as electron conductivity: the ferromagnetic moments are easily polarized even by a tiny field of 1 mT at high temperature, while, once cooled down, they are surprisingly robust even in an inverse magnetic field of 7 T. Thus, the magnetic domain walls could serve as a new-type of microscopic, switchable and electrically readable magnetic medium which is potentially important for future applications in the domain wall nanoelectronics.
On thick domain walls in general relativity
Goetz, Guenter; Noetzold, Dirk
1989-01-01
Planar scalar field configurations in general relativity differ considerably from those in flat space. It is shown that static domain walls of finite thickness in curved space-time do not possess a reflection symmetry. At infinity, the space-time tends to the Taub vacuum on one side of the wall and to the Minkowski vacuum (Rindler space-time) on the other. Massive test particles are always accelerated towards the Minkowski side, i.e., domain walls are attractive on the Taub side, but repulsive on the Minkowski side (Taub-vacuum cleaner). It is also proved that the pressure in all directions is always negative. Finally, a brief comment is made concerning the possibility of infinite, i.e., bigger than horizon size, domain walls in our universe. All of the results are independent of the form of the potential V(phi) greater than or equal to 0 of the scalar field phi.
Anomalous feedback and negative domain wall resistance
Cheng, Ran; Zhu, Jian-Gang; Xiao, Di
2016-11-01
Magnetic induction can be regarded as a negative feedback effect, where the motive-force opposes the change of magnetic flux that generates the motive-force. In artificial electromagnetics emerging from spintronics, however, this is not necessarily the case. By studying the current-induced domain wall dynamics in a cylindrical nanowire, we show that the spin motive-force exerting on electrons can either oppose or support the applied current that drives the domain wall. The switching into the anomalous feedback regime occurs when the strength of the dissipative torque β is about twice the value of the Gilbert damping constant α. The anomalous feedback manifests as a negative domain wall resistance, which has an analogy with the water turbine.
Multigrid Algorithms for Domain-Wall Fermions
Cohen, Saul D; Clark, M A; Osborn, J C
2012-01-01
We describe an adaptive multigrid algorithm for solving inverses of the domain-wall fermion operator. Our multigrid algorithm uses an adaptive projection of near-null vectors of the domain-wall operator onto coarser four-dimensional lattices. This extension of multigrid techniques to a chiral fermion action will greatly reduce overall computation cost, and the elimination of the fifth dimension in the coarse space reduces the relative cost of using chiral fermions compared to discarding this symmetry. We demonstrate near-elimination of critical slowing as the quark mass is reduced and small volume dependence, which may be suppressed by taking advantage of the recursive nature of the algorithm.
Metastable magnetic domain walls in cylindrical nanowires
Energy Technology Data Exchange (ETDEWEB)
Ferguson, C.A.; MacLaren, D.A.; McVitie, S., E-mail: Stephen.McVitie@glasgow.ac.uk
2015-05-01
The stability of the asymmetric domain wall (ATDW) in soft magnetic cylindrical nanowires and nanotubes is investigated using micromagnetic simulations. Our calculated phase diagram shows that for cylindrical permalloy nanowires, the transverse domain wall (TDW) is the ground state for radii below 20 nm whilst the Bloch point wall (BPW) is favoured in thicker wires. The ATDW stabilises only as a metastable state but with energy close to that of the BPW. Characterisation of the DW spin structures reveals that the ATDW has a vortex-like surface spin state, in contrast to the divergent surface spins of the TDW. This results in lowering of surface charge above the critical radius. For both cylindrical nanotubes and nanowires we find that ATDWs only appear to exist as metastable static states and are particularly suppressed in nanotubes due to an increase in magnetostatic energy. - Highlights: • We simulate the micromagnetic structures of domain walls in cylindrical nanowires. • A phase diagram identifies ground and metastable states. • Asymmetric transverse walls are metastable in nanowires but suppressed in tubes. • Unrolling surface magnetisation aids visualisation of asymmetry and chirality. • We predict experimental discrimination based on magnetic charge distribution.
Compactified webs and domain wall partition functions
Energy Technology Data Exchange (ETDEWEB)
Shabbir, Khurram [Government College University, Department of Mathematics, Lahore (Pakistan)
2017-04-15
In this paper we use the topological vertex formalism to calculate a generalization of the ''domain wall'' partition function of M-strings. This generalization allows calculation of partition function of certain compactified webs using a simple gluing algorithm similar to M-strings case. (orig.)
Domain wall partition functions and KP
Foda, O; Zuparic, M
2009-01-01
We observe that the partition function of the six vertex model on a finite square lattice with domain wall boundary conditions is (a restriction of) a KP tau function and express it as an expectation value of charged free fermions (up to an overall normalization).
Domain wall dynamics of magnetically bistable microwires
Directory of Open Access Journals (Sweden)
Ipatov M.
2012-06-01
Full Text Available We studied domain wall propagation of magnetically-bistable Fe- Co-rich microwires paying attention on effect of applied and internal stresses. We measured hysteresis loops and domain wall propagation in various magnetic Fe- Co-rich amorphous microwires with metallic nucleus diameters (from 12 □m till 22 □m using Sixtus Tonks-like experiments. Application of tensile stresses results in decreasing of domain wall velocity. We discussed magnetoelastic contribution in dynamics of domain wall propagation. We observed, that microwires with different geometries exhibit v(H dependences with different slopes. Application of stresses resulted in decrease of DW velocity, v, and DW mobility S. Quite fast DW propagation (v till 2500 m/s at H about 30 A/m has been observed in low magnetostrictive magnetically bistable Co56Fe8Ni10Si110B16 microwires. Consequently, we can assume that generally magnetoelastic energy affects DW dynamics: decreasing magnetoelastic energy, Kme, DW velocity increases.
Fast domain wall dynamics in amorphous and nanocrystalline magnetic microwires
Energy Technology Data Exchange (ETDEWEB)
Varga, R., E-mail: rvarga@upjs.sk [Institute of Physics, Faculty of Science, UPJS, Park Angelinum 9, 041 54, Kosice (Slovakia); Klein, P.; Richter, K. [Institute of Physics, Faculty of Science, UPJS, Park Angelinum 9, 041 54, Kosice (Slovakia); Zhukov, A. [Dept. Fisica de Materiales, Fac. Quimica, UPV/EHU, San Sebastian (Spain); Vazquez, M. [Instituto de Ciencia de Materiales de Madrid, CSIC, Sor Juana Ines de la Cruz 3, 28049 Cantoblanco, Madrid (Spain)
2012-10-15
We have studied the effect of thermal treatment on the domain wall dynamics of FeSiB and FeCoMoB microwires. It was shown that annealing in transversal magnetic field increases the domain wall mobility as well as the domain wall velocity. Annealing under the tensile stress hinders the appearance of the monodomain structure but application of tensile stress leads to the magnetic bistability having the domain wall mobility twice higher that in as-cast state. Further increase of the tensile stress reduces the domain wall mobility but the domain wall velocity increases as a result of the decrease of critical propagation field. Annealing of the FeCoMoB microwire by Joule heating leads to introduction of the circular anisotropy that favors the vortex domain wall. Such treatment increases the domain wall mobility as well as the maximum domain wall velocity.
Antiferromagnetic domain wall motion driven by spin-orbit torques
Shiino, Takayuki; Oh, Se-Hyeok; Haney, Paul M.; Lee, Seo-Won; Go, Gyungchoon; Park, Byong-Guk; Lee, Kyung-Jin
2016-01-01
We theoretically investigate dynamics of antiferromagnetic domain walls driven by spin-orbit torques in antiferromagnet/heavy metal bilayers. We show that spin-orbit torques drive antiferromagnetic domain walls much faster than ferromagnetic domain walls. As the domain wall velocity approaches the maximum spin-wave group velocity, the domain wall undergoes Lorentz contraction and emits spin-waves in the terahertz frequency range. The interplay between spin-orbit torques and the relativistic dynamics of antiferromagnetic domain walls leads to the efficient manipulation of antiferromagnetic spin textures and paves the way for the generation of high frequency signals from antiferromagnets. PMID:27588878
Skyrmion domain wall collision and domain wall-gated skyrmion logic
Xing, Xiangjun; Pong, Philip W. T.; Zhou, Yan
2016-08-01
Skyrmions and domain walls are significant spin textures of great technological relevance to magnetic memory and logic applications, where they can be used as carriers of information. The unique topology of skyrmions makes them display emergent dynamical properties as compared with domain walls. Some studies have demonstrated that the two topologically inequivalent magnetic objects could be interconverted by using cleverly designed geometric structures. Here, we numerically address the skyrmion domain wall collision in a magnetic racetrack by introducing relative motion between the two objects based on a specially designed junction. An electric current serves as the driving force that moves a skyrmion toward a trapped domain wall pair. We see different types of collision dynamics depending on the driving parameters. Most importantly, the modulation of skyrmion transport using domain walls is realized in this system, allowing a set of domain wall-gated logical NOT, NAND, and NOR gates to be constructed. This work provides a skyrmion-based spin-logic architecture that is fully compatible with racetrack memories.
Energy Technology Data Exchange (ETDEWEB)
Rodriguez-Rodriguez, G; Hierro-Rodriguez, A; Perez-Junquera, A; Montenegro, N; Alameda, J M; Velez, M [Dept. Fisica, Universidad de Oviedo-CINN, 33007 Oviedo (Spain); Menendez, J L [Centro de Investigacion en Nanomateriales y Nanotecnologia (CINN). Principado de Asturias-Consejo Superior de Investigaciones Cientificas (CSIC)-Univ. Oviedo -UO, Parque Tecnologico de Asturias, 33428 Llanera (Spain); Ravelosona, D, E-mail: mvelez@uniovi.e [Institut d' Electronique Fondamentale, UMR CNRS 8622, Univ. Paris Sud, 91405 Orsay Cedex (France)
2010-08-04
The interplay between collective pinning on intrinsic structural defects and artificial pinning at a patterned hole is studied in magnetic multilayers with perpendicular anisotropy. The pinning strength of a patterned hole is measured through its efficiency to stop domain wall (DW) propagation into a consecutive unpatterned nanowire section (using antisymmetric magnetoresistance to detect the direction of DW propagation) whereas collective pinning is characterized by the field dependence of DW velocity. Close to room temperature, collective pinning becomes weaker than artificial pinning so that pinning at the hole compensates nucleation-pad geometry, blocking DW propagation across the nanowire.
Magnetic domain wall manipulation in (Ga,Mn)As nanostructures for spintronic applications
Wosinski, Tadeusz; Andrearczyk, Tomasz; Figielski, Tadeusz; Olender, Karolina; Wrobel, Jerzy; Sadowski, Janusz
2014-02-01
Ring-shaped nanostructures have been designed and fabricated by electron-beam lithography patterning and chemical etching from thin epitaxial layers of the ferromagnetic semiconductor (Ga,Mn)As. The nanostructures, in a form of planar rings with a slit, were supplied with four electrical terminals and subjected to magneto-transport studies under planar weak magnetic field. Magnetoresistive effects caused by manipulation of magnetic domain walls and magnetization reversal in the nanostructures have been investigated and possible applications of the nanostructures as four-terminal spintronic devices are discussed.
Magnetic domain wall manipulation in (Ga,Mn)As nanostructures for spintronic applications
Energy Technology Data Exchange (ETDEWEB)
Wosinski, Tadeusz; Andrearczyk, Tomasz; Figielski, Tadeusz; Olender, Karolina; Wrobel, Jerzy [Institute of Physics, Polish Academy of Sciences, Al. Lotnikow 32/46, PL-02-668 Warsaw (Poland); Sadowski, Janusz [Institute of Physics, Polish Academy of Sciences, Al. Lotnikow 32/46, PL-02-668 Warsaw, Poland and MAX-IV Laboratory, Lund University, P.O. Box 118, SE-221 00 Lund (Sweden)
2014-02-21
Ring-shaped nanostructures have been designed and fabricated by electron-beam lithography patterning and chemical etching from thin epitaxial layers of the ferromagnetic semiconductor (Ga,Mn)As. The nanostructures, in a form of planar rings with a slit, were supplied with four electrical terminals and subjected to magneto-transport studies under planar weak magnetic field. Magnetoresistive effects caused by manipulation of magnetic domain walls and magnetization reversal in the nanostructures have been investigated and possible applications of the nanostructures as four-terminal spintronic devices are discussed.
Magnetic domain-wall racetrack memory.
Parkin, Stuart S P; Hayashi, Masamitsu; Thomas, Luc
2008-04-11
Recent developments in the controlled movement of domain walls in magnetic nanowires by short pulses of spin-polarized current give promise of a nonvolatile memory device with the high performance and reliability of conventional solid-state memory but at the low cost of conventional magnetic disk drive storage. The racetrack memory described in this review comprises an array of magnetic nanowires arranged horizontally or vertically on a silicon chip. Individual spintronic reading and writing nanodevices are used to modify or read a train of approximately 10 to 100 domain walls, which store a series of data bits in each nanowire. This racetrack memory is an example of the move toward innately three-dimensional microelectronic devices.
Domain wall magneto-Seebeck effect
Krzysteczko, Patryk; Hu, Xiukun; Liebing, Niklas; Sievers, Sibylle; Schumacher, Hans W.
2014-01-01
The interplay between charge, spin, and heat currents in magnetic nano systems subjected to a temperature gradient has lead to a variety of novel effects and promising applications studied in the fast-growing field of spincaloritronics. Here we explore the magnetothermoelectrical properties of an individual magnetic domain wall in a permalloy nanowire. In thermal gradients of the order of few Kelvin per micrometer along the long wire axis, we find a clear magneto-Seebeck signature due to the ...
BPS domain walls from backreacted orientifolds
Blåbäck, Johan; Van Riet, Thomas; Vercnocke, Bert
2013-01-01
Compactifications with D-brane and orientifold sources lead to standard gauged supergravity theories if the sources are smeared over the internal directions. It is therefore of interest to find how the solutions described by the gauged supergravity are altered by properly localising the sources. In this paper we analyse this for BPS domain wall solutions in the seven-dimensional gauged supergravity obtained from an O6 toroidal orientifold compactification in massive IIA supergravity. This is one of the simplest no-scale supergravities that can be constructed and analysed in full detail. We find and discuss the BPS domain walls both when the O6 planes are smeared and localised. When the O6 planes are localised the domain wall solutions live in a warped compactification. In order to get explicit expressions we also consider the non-compact versions of the solutions for which the O6 planes have been traded for D6 branes. Through T-duality we obtain partially localised solutions for compactifications to four dime...
PREFACE: Domain wall dynamics in nanostructures Domain wall dynamics in nanostructures
Marrows, C. H.; Meier, G.
2012-01-01
Domain structures in magnetic materials are ubiquitous and have been studied for decades. The walls that separate them are topological defects in the magnetic order parameter and have a wide variety of complex forms. In general, their investigation is difficult in bulk materials since only the domain structure on the surface of a specimen is visible. Cutting the sample to reveal the interior causes a rearrangement of the domains into a new form. As with many other areas of magnetism, the study of domain wall physics has been revitalised by the advent of nanotechnology. The ability to fabricate nanoscale structures has permitted the formation of simplified and controlled domain patterns; the development of advanced microscopy methods has permitted them to be imaged and then modelled; subjecting them to ultrashort field and current pulses has permitted their dynamics to be explored. The latest results from all of these advances are described in this special issue. Not only has this led to results of great scientific beauty, but also to concepts of great applicability to future information technologies. In this issue the reader will find the latest results for these domain wall dynamics and the high-speed processes of topological structures such as domain walls and magnetic vortices. These dynamics can be driven by the application of magnetic fields, or by flowing currents through spintronic devices using the novel physics of spin-transfer torque. This complexity has been studied using a wide variety of experimental techniques at the edge of the spatial and temporal resolution currently available, and can be described using sophisticated analytical theory and computational modelling. As a result, the dynamics can be engineered to give rise to finely controlled memory and logic devices with new functionality. Moreover, the field is moving to study not only the conventional transition metal ferromagnets, but also complex heterostructures, novel magnets and even other
Switching of ± 360° domain wall states in a nanoring by an azimuthal Oersted field.
Pradhan, N R; Licht, A S; Li, Y; Sun, Y; Tuominen, M T; Aidala, K E
2011-12-02
We demonstrate magnetic switching between two 360° domain wall vortex states in cobalt nanorings, which are candidate magnetic states for robust and low power magnetoresistive random access memory (MRAM) devices. These 360° domain wall (DW) or 'twisted onion' states can have clockwise or counterclockwise circulation, the two states for data storage. Reliable switching between the states is necessary for any realistic device. We accomplish this switching by applying a circular Oersted field created by passing current through a metal atomic force microscope tip placed at the center of the ring. After initializing in an onion state, we rotate the DWs to one side of the ring by passing a current through the center, and can switch between the two twisted states by reversing the current, causing the DWs to split and meet again on the opposite side of the ring. A larger current will annihilate the DWs and create a perfect vortex state in the rings.
Strain-controlled magnetic domain wall propagation in hybrid piezoelectric/ferromagnetic structures
Lei, Na; Devolder, Thibaut; Agnus, Guillaume; Aubert, Pascal; Daniel, Laurent; Kim, Joo-Von; Zhao, Weisheng; Trypiniotis, Theodossis; Cowburn, Russell P.; Chappert, Claude; Ravelosona, Dafiné; Lecoeur, Philippe
2013-01-01
The control of magnetic order in nanoscale devices underpins many proposals for integrating spintronics concepts into conventional electronics. A key challenge lies in finding an energy-efficient means of control, as power dissipation remains an important factor limiting future miniaturization of integrated circuits. One promising approach involves magnetoelectric coupling in magnetostrictive/piezoelectric systems, where induced strains can bear directly on the magnetic anisotropy. While such processes have been demonstrated in several multiferroic heterostructures, the incorporation of such complex materials into practical geometries has been lacking. Here we demonstrate the possibility of generating sizeable anisotropy changes, through induced strains driven by applied electric fields, in hybrid piezoelectric/spin-valve nanowires. By combining magneto-optical Kerr effect and magnetoresistance measurements, we show that domain wall propagation fields can be doubled under locally applied strains. These results highlight the prospect of constructing low-power domain wall gates for magnetic logic devices.
Single domain wall manipulation in curved nanowires using a mobile, local, circular field
Shortt, Madeline; Bickel, Jessica; Khan, Mina; Tuominen, Mark; Aidala, Katherine
2014-03-01
Ferromagnetic nanostructures present exciting physics with a range of potential applications in data storage devices, such as magnetoresistive random access memory (MRAM). These proposals require precise control and understanding of domain wall (DW) movement and interactions. We developed a technique that generates a local circular Oersted field at a precise location by applying current through the tip of the atomic force microscope (AFM). We previously used this technique to control DW motion in nanorings. We extend this method to control individual DW movement in curved nanowires by placing the tip near a 180 DW at the vertex of a curved wire and generating a local field. In this way, we can examine the motion of domain walls through regions with different curvature and the effects of pinning. This work was supported in part by NSF DMR-1207924 and the UMass Center for Hierarchical Manufacturing, NSF CMMI-1025020.
Low field domain wall dynamics in artificial spin-ice basis structure
Energy Technology Data Exchange (ETDEWEB)
Kwon, J. [School of Physical and Mathematical Sciences, Nanyang Technological University, 21 Nanyang Link, Singapore 637371 (Singapore); School of Electrical and Electronic Engineering, Nanyang Technological University, 50 Nanyang Avenue, Singapore 639798 (Singapore); Goolaup, S.; Lim, G. J.; Kerk, I. S.; Lew, W. S., E-mail: wensiang@ntu.edu.sg [School of Physical and Mathematical Sciences, Nanyang Technological University, 21 Nanyang Link, Singapore 637371 (Singapore); Chang, C. H., E-mail: echchang@ntu.edu.sg [School of Electrical and Electronic Engineering, Nanyang Technological University, 50 Nanyang Avenue, Singapore 639798 (Singapore); Roy, K. [School of Electrical and Computer Engineering, Purdue University, West Lafayette, Indiana 47907 (United States)
2015-10-28
Artificial magnetic spin-ice nanostructures provide an ideal platform for the observation of magnetic monopoles. The formation of a magnetic monopole is governed by the motion of a magnetic charge carrier via the propagation of domain walls (DWs) in a lattice. To date, most experiments have been on the static visualization of DW propagation in the lattice. In this paper, we report on the low field dynamics of DW in a unit spin-ice structure measured by magnetoresistance changes. Our results show that reversible DW propagation can be initiated within the spin-ice basis. The initial magnetization configuration of the unit structure strongly influences the direction of DW motion in the branches. Single or multiple domain wall nucleation can be induced in the respective branches of the unit spin ice by the direction of the applied field.
Institute of Scientific and Technical Information of China (English)
Wei Hong-Xiang; Lu Qing-Feng; Zhao Su-Fen; Zhang Xie-Qun; Feng Jia-Feng; Han Xiu-Feng
2004-01-01
Microfabrication and the magneto-transport characteristics of the magnetic tunnel junctions (MTJs) with a spin-valve-type structure of Ta (5nm)/Ni7gFe21 (25nm)/Ir22Mn78 (12nm)/Co75Fe25 (4nm)/Al(0.8nm) oxide/Co75Fe25(4nm)/Ni7gFe21 (20nm)/Ta(5nm) were investigated in this paper. A series of experimental data measured with a MTJ was used to verify a magnon-assisted tunnelling model and theory. Furthermore, a micromagnetics simulation shows that the butterfly-like vortex domain structures can be formed under a current-induced Oersted field, which decreases the net magnetization values of the ferromagnetic electrodes under a large dc current (i.e., in high voltage regimes). It is one of the main reasons for the tunnel magnetoresistance ratios to decrease significantly at high voltage biasing.
Thermal and Quantum Fluctuations around Domain Walls
Aragão de Carvalho, C
2002-01-01
We compute thermal and quantum fluctuations in the background of a domain wall in a scalar field theory at finite temperature using the exact scalar propagator in the subspace orthogonal to the wall's translational mode. The propagator makes it possible to calculate terms of any order in the semiclassical expansion of the partition function of the system. The leading term in the expansion corresponds to the fluctuation determinant, which we compute for arbitrary temperature in space dimensions 1,2, and 3. Our results may be applied to the description of thermal scalar propagation in the presence of soliton defects (in polymers, magnetic materials, etc.) and interfaces which are characterized by kinklike profiles. They lead to predictions as to how classical free energies, surface tensions, and interface profiles are modified by fluctuations, allowing for comparison with both numerical and experimental data. They can also be used to estimate transition temperatures. Furthermore, the simple analytic form of the...
Energy Technology Data Exchange (ETDEWEB)
Hempe, E.M. [Department of Materials Science and Metallurgy, University of Cambridge, Pembroke Street, Cambridge CB2 3QZ (United Kingdom); Department of Physics, Universitaet Regensburg, Universitaetsstrasse 31, 93040 Regensburg (Germany); Klaeui, M.; Krzyk, S.; Ruediger, U. [Fachbereich Physik, Universitaet Konstanz, Universitaetsstrasse 10, 78457 Konstanz (Germany); Kasama, T. [Department of Materials Science and Metallurgy, University of Cambridge, Pembroke Street, Cambridge CB2 3QZ (United Kingdom); Backes, D. [Fachbereich Physik, Universitaet Konstanz, Universitaetsstrasse 10, 78457 Konstanz (Germany); Laboratory for Micro- and Nanotechnology, Paul Scherrer Institut, 5232 Villigen PSI (Switzerland); Junginger, F. [Department of Materials Science and Metallurgy, University of Cambridge, Pembroke Street, Cambridge CB2 3QZ (United Kingdom); Fachbereich Physik, Universitaet Konstanz, Universitaetsstrasse 10, 78457 Konstanz (Germany); Heyderman, L.J. [Laboratory for Micro- and Nanotechnology, Paul Scherrer Institut, 5232 Villigen PSI (Switzerland); Dunin-Borkowski, R. [Department of Materials Science and Metallurgy, University of Cambridge, Pembroke Street, Cambridge CB2 3QZ (United Kingdom); Center for Electron Nanoscopy, DTU (Denmark)
2007-12-15
We report the direct transmission electron microscopy observation of spin structure transformations in nanoscale Permalloy zigzag wires due to Joule heating during the injection of current pulses. This heating is sufficient to overcome the energy barriers separating the different metastable domain wall spin structures. Due to the large energy barriers these are stable and observable at room temperature by off-axis electron holography and Fresnel imaging. The interaction between different domain walls is probed and the main pinning mechanism is determined to be the edge roughness. In addition to transformations, we also report on thermally assisted domain wall hopping between two pinning sites and structural changes that occur when the samples are subjected to even higher current pulses. (copyright 2008 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)
Casimir effect in Domain Wall formation
Setare, M R
2003-01-01
The Casimir forces on two parallel plates in conformally flat de Sitter background due to conformally coupled massless scalar field satisfying mixed boundary conditions on the plates is investigated. In the general case of mixed boundary conditions formulae are derived for the vacuum expectation values of the energy-momentum tensor and vacuum forces acting on boundaries. Different cosmological constants are assumed for the space between and outside of the plates to have general results applicable to the case of domain wall formations in the early universe.
Polarization control at spin-driven ferroelectric domain walls
Leo, Naëmi; Bergman, Anders; Cano, Andres; Poudel, Narayan; Lorenz, Bernd; Fiebig, Manfred; Meier, Dennis
2015-04-01
Unusual electronic states arise at ferroelectric domain walls due to the local symmetry reduction, strain gradients and electrostatics. This particularly applies to improper ferroelectrics, where the polarization is induced by a structural or magnetic order parameter. Because of the subordinate nature of the polarization, the rigid mechanical and electrostatic boundary conditions that constrain domain walls in proper ferroics are lifted. Here we show that spin-driven ferroelectricity promotes the emergence of charged domain walls. This provides new degrees of flexibility for controlling domain-wall charges in a deterministic and reversible process. We create and position a domain wall by an electric field in Mn0.95Co0.05WO4. With a magnetic field we then rotate the polarization and convert neutral into charged domain walls, while its magnetic properties peg the wall to its location. Using atomistic Landau-Lifshitz-Gilbert simulations we quantify the polarization changes across the two wall types and highlight their general occurrence.
Origin of stationary domain wall enhanced ferroelectric susceptibility
Liu, Shi; Cohen, R. E.
2017-03-01
Ferroelectrics usually adopt a multidomain state with domain walls separating domains with polarization axes oriented differently. It has long been recognized that domain walls can dramatically impact the properties of ferroelectric materials. The enhancement of low-field susceptibility/permittivity under subswitching conditions is usually attributed to reversible domain wall vibration. Recent experiments highlight the stationary domain wall contribution to the dielectric susceptibility irrespective of any lateral displacements or deformations of the wall. We study the effects of domain walls on the low-field permittivity of PbTiO3 with density functional theory and molecular dynamics simulations. The static dielectric constant is calculated as a function of increasing domain wall density and temperature. We find an increase of dielectric permittivity with increasing domain wall density, which is expected to occur at a low driving field where the lateral motion of domain walls is forbidden. Real-space decomposition of the dielectric response reveals that frustrated dipoles within the finite width of the domain walls are responsible for the enhanced low-field permittivity. We explain the 100 % enhancement of the dielectric susceptibility form domain walls, which arises from the softer potential wells within them.
Domain Wall Mobility in Co-Based Amorphous Wire
Directory of Open Access Journals (Sweden)
Maria Kladivova
2007-01-01
Full Text Available Dynamics of the domain wall between opposite circularly magnetized domains in amorphous cylindrical sample with circular easy direction is theoretically studied. The wall is driven by DC current. Various mechanisms which influence the wall velocity were taken into account: current magnitude, deformation of the mowing wall, Hall effect, axially magnetized domain in the middle of the wire. Theoretical results obtained are in a good agreement with experiments on Cobased amorphous ferromagnetic wires.
Second-harmonic imaging of ferroelectric domain walls
DEFF Research Database (Denmark)
Bozhevolnyi, Sergey I.; Hvam, Jørn Märcher; Pedersen, Kjeld;
1998-01-01
Domain walls in periodically poled ferroelectric KTiOPO4 and LiNbO3 crystals are observed by making use of second-harmonic (SH) generation enhancement in the transition regions between neighboring domains. SH images of domain walls obtained with various samples for different polarization...
Power optimization for domain wall motion in ferromagnetic nanowires
Tretiakov, O. A.; Liu, Y.; Abanov, Ar.
2011-04-01
The current mediated domain-wall dynamics in a thin ferromagnetic wire is investigated. We derive the effective equations of motion of the domain wall. They are used to study the possibility to optimize the power supplied by electric current for the motion of domain walls in a nanowire. We show that a certain resonant time-dependent current moving a domain wall can significantly reduce the Joule heating in the wire, and thus it can lead to a novel proposal for the most energy efficient memory devices. We discuss how Gilbert damping, nonadiabatic spin transfer torque, and the presence of Dzyaloshinskii-Moriya interaction can effect this power optimization.
Power optimization for domain wall motion in ferromagnetic nanowires
Tretiakov, Oleg A.; Liu, Y.; Abanov, Ar.
2010-01-01
The current mediated domain-wall dynamics in a thin ferromagnetic wire is investigated. We derive the effective equations of motion of the domain wall. They are used to study the possibility to optimize the power supplied by electric current for the motion of domain walls in a nanowire. We show that a certain resonant time-dependent current moving a domain wall can significantly reduce the Joule heating in the wire, and thus it can lead to a novel proposal for the most energy efficient memory...
Hamilton-Jacobi method for curved domain walls and cosmologies
Skenderis, Kostas; Townsend, Paul K.
2006-12-01
We use Hamiltonian methods to study curved domain walls and cosmologies. This leads naturally to first-order equations for all domain walls and cosmologies foliated by slices of maximal symmetry. For Minkowski and AdS-sliced domain walls (flat and closed FLRW cosmologies) we recover a recent result concerning their (pseudo)supersymmetry. We show how domain-wall stability is consistent with the instability of AdS vacua that violate the Breitenlohner-Freedman bound. We also explore the relationship to Hamilton-Jacobi theory and compute the wave-function of a 3-dimensional closed universe evolving towards de Sitter spacetime.
Effective pinning energy landscape perturbations for propagating magnetic domain walls
Burn, D. M.; Atkinson, D.
2016-01-01
The interaction between a magnetic domain wall and a pinning site is explored in a planar nanowire using micromagnetics to reveal perturbations of the pinning energetics for propagating domain walls. Numerical simulations in the high damping ’quasi-static’ and low damping ’dynamic’ regimes are compared and show clear differences in de-pinning fields, indicating that dynamical micromagnetic models, which incorporate precessionally limited magnetization processes, are needed to understand domain wall pinning. Differences in the micromagnetic domain wall structure strongly influence the pinning and show periodic behaviour with increasing applied field associated with Walker breakdown. In the propagating regime pinning is complicated. PMID:27694953
Van de Wiele, Ben; Leliaert, Jonathan; Franke, Kévin; van Dijken, Sebastiaan
2016-01-01
Strong coupling of magnetic domain walls onto straight ferroelastic boundaries of a ferroelectric layer enables full and reversible electric-field control of magnetic domain wall motion. In this paper, the dynamics of this new driving mechanism is analyzed using micromagnetic simulations. We show that transverse domain walls with a near-180° spin structure are stabilized in magnetic nanowires and that electric fields can move these walls with high velocities. Above a critical velocity, which ...
Supercurrent enhancement in Bloch domain walls.
Robinson, J W A; Chiodi, F; Egilmez, M; Halász, Gábor B; Blamire, M G
2012-01-01
Conventional spin-singlet Cooper pairs convert into spin-triplet pairs in ferromagnetic Josephson junctions in which the superconductor/ferromagnet interfaces (S/F) are magnetically inhomogeneous. Although much of the theoretical work describing this triplet proximity effect has considered ideal junctions with magnetic domain walls (DW) at the interfaces, in practice it is not easily possible to isolate a DW and propagate a supercurrent through it. The rare-earth magnet Gd can form a field-tuneable in-plane Bloch DW if grown between non-co-linearly aligned ferromagnets. Here we report supercurrents through magnetic Ni-Gd-Ni nanopillars: by field annealing at room temperature, we are able to modify the low temperature DW-state in Gd and this result has a striking effect on the junction supercurrent at 4.2 K. We argue that this result can only be explained in terms of the interconversion of triplet and singlet pairs, the efficiency of which depends on the magnetic helicity of the structure.
Chiral damping of magnetic domain walls
Jué, Emilie
2015-12-21
Structural symmetry breaking in magnetic materials is responsible for the existence of multiferroics1, current-induced spin–orbit torques2, 3, 4, 5, 6, 7 and some topological magnetic structures8, 9, 10, 11, 12. In this Letter we report that the structural inversion asymmetry (SIA) gives rise to a chiral damping mechanism, which is evidenced by measuring the field-driven domain-wall (DW) motion in perpendicularly magnetized asymmetric Pt/Co/Pt trilayers. The DW dynamics associated with the chiral damping and those with Dzyaloshinskii–Moriya interaction (DMI) exhibit identical spatial symmetry13, 14, 15, 16, 17, 18, 19. However, both scenarios are differentiated by their time reversal properties: whereas DMI is a conservative effect that can be modelled by an effective field, the chiral damping is purely dissipative and has no influence on the equilibrium magnetic texture. When the DW motion is modulated by an in-plane magnetic field, it reveals the structure of the internal fields experienced by the DWs, allowing one to distinguish the physical mechanism. The chiral damping enriches the spectrum of physical phenomena engendered by the SIA, and is essential for conceiving DW and skyrmion devices owing to its coexistence with DMI (ref. 20).
Chiral damping of magnetic domain walls
Jué, Emilie; Safeer, C. K.; Drouard, Marc; Lopez, Alexandre; Balint, Paul; Buda-Prejbeanu, Liliana; Boulle, Olivier; Auffret, Stephane; Schuhl, Alain; Manchon, Aurelien; Miron, Ioan Mihai; Gaudin, Gilles
2016-03-01
Structural symmetry breaking in magnetic materials is responsible for the existence of multiferroics, current-induced spin-orbit torques and some topological magnetic structures. In this Letter we report that the structural inversion asymmetry (SIA) gives rise to a chiral damping mechanism, which is evidenced by measuring the field-driven domain-wall (DW) motion in perpendicularly magnetized asymmetric Pt/Co/Pt trilayers. The DW dynamics associated with the chiral damping and those with Dzyaloshinskii-Moriya interaction (DMI) exhibit identical spatial symmetry. However, both scenarios are differentiated by their time reversal properties: whereas DMI is a conservative effect that can be modelled by an effective field, the chiral damping is purely dissipative and has no influence on the equilibrium magnetic texture. When the DW motion is modulated by an in-plane magnetic field, it reveals the structure of the internal fields experienced by the DWs, allowing one to distinguish the physical mechanism. The chiral damping enriches the spectrum of physical phenomena engendered by the SIA, and is essential for conceiving DW and skyrmion devices owing to its coexistence with DMI (ref. ).
On domain-wall/QFT dualities in various dimensions
Behrndt, Klaus; Bergshoeff, Eric; Halbersma, Rein; Schaar, Jan Pieter van der
1999-01-01
We investigate domain-wall/quantum field-theory correspondences in various dimensions. Our general analysis covers not only the well studied cases in 10 and 11 dimensions, but also enables us to discuss new cases like a type I/heterotic 6-brane in 10 dimensions and domain-wall dualities in lower
Efficient and controlled domain wall nucleation for magnetic shift registers.
Alejos, Oscar; Raposo, Víctor; Sanchez-Tejerina, Luis; Martinez, Eduardo
2017-09-19
Ultrathin ferromagnetic strips with high perpendicular anisotropy have been proposed for the development of memory devices where the information is coded in tiny domains separated by domain walls. The design of practical devices requires creating, manipulating and detecting domain walls in ferromagnetic strips. Recent observations have shown highly efficient current-driven domain wall dynamics in multilayers lacking structural symmetry, where the walls adopt a chiral structure and can be driven at high velocities. However, putting such a device into practice requires the continuous and synchronous injection of domain walls as the first step. Here, we propose and demonstrate an efficient and simple scheme for nucleating domain walls using the symmetry of the spin orbit torques. Trains of short sub-nanosecond current pulses are injected in a double bit line to generate a localized longitudinal Oersted field in the ferromagnetic strip. Simultaneously, other current pulses are injected through the heavy metal under the ferromagnetic strip. Notably, the Slonczewski-like spin orbit torque assisted by the Oersted field allows the controlled injection of a series of domain walls, giving rise to a controlled manner for writing binary information and, consequently, to the design of a simple and efficient domain wall shift register.
Nanomagnetic engineering of the properties of domain wall atom traps
Hayward, Thomas J; Weatherill, Kevin J; Schrefl, Thomas; Hughes, Ifan G; Allwood, Dan A
2011-01-01
We have used the results of micromagnetic simulations to investigate the effects of nanowire geometry and domain wall magnetization structure on the characteristic parameters of magnetic atom traps formed by domain walls in planar ferromagnetic nanowires. It is found that when traps are formed in the near-field of a domain wall both nanowire geometry and wall structure have a substantial effect on trap frequency and adiabaticity. We also show that in certain regimes a trap's depth depends only on the amplitude of an externally applied rotating magnetic field, thus allowing it to be tuned independently of the trap's other critical parameters.
Scalar triplet on a domain wall: an exact solution
Gani, Vakhid A; Radomskiy, Roman V
2016-01-01
We study a model with a real scalar Higgs field and a scalar triplet field that allows existence of a topological defect -- a domain wall. The wall breaks the global $O(3)$ symmetry of the model, which gives rise to non-Abelian orientational degrees of freedom. We found an exact analytic solution that describes a domain wall with a localized configuration of the triplet field on it. This solution enables one to calculate contributions to the action from the orientational and translational degrees of freedom of the triplet field. We also study the linear stability of the domain wall with the triplet field switched off.
A "Domain Wall" Scenario for the AdS/QCD
Shuryak, Edward
2007-01-01
We propose a scenario for bottom-up gravity dual picture of QCD-like theories, which consists of two near-AdS$_5$ domains separated by the "domain wall" at which the effective coupling relatively rapidly switches from small perturbative value at its UV side to strong at its IR side. The proposed mechanism for this jump is related to instantons, which are located at/near this wall. We further argue that in the limit of large number of colors $N_c\\to\\infty$ the "domain wall" is becoming a singularity. The instanton liquid model is reformulated in $AdS_5$ language, where instantons became point-like quark vertices on the domain wall. Among applications one may consider lowest mesons as collective vibrations of this "wall". We suggest that the "wall" can be observed in a strong-to-weak transitions of various QCD processes and provide estimate for jump magnitude for various exclusive processes.
Contribution of domain wall networks to the CMB power spectrum
Lazanu, A; Shellard, E P S
2015-01-01
We use three domain wall simulations from the radiation era to the late time dark energy domination era based on the PRS algorithm to calculate the energy-momentum tensor components of domain wall networks in an expanding universe. Unequal time correlators in the radiation, matter and cosmological constant epochs are calculated using the scaling regime of each of the simulations. The CMB power spectrum of a network of domain walls is determined. The first ever quantitative constraint for the domain wall surface tension is obtained using a Markov chain Monte Carlo method; an energy scale of domain walls of 0.93 MeV, which is close but below the Zel'dovich bound, is determined.
Contribution of domain wall networks to the CMB power spectrum
Directory of Open Access Journals (Sweden)
A. Lazanu
2015-07-01
Full Text Available We use three domain wall simulations from the radiation era to the late-time dark energy domination era based on the PRS algorithm to calculate the energy–momentum tensor components of domain wall networks in an expanding universe. Unequal time correlators in the radiation, matter and cosmological constant epochs are calculated using the scaling regime of each of the simulations. The CMB power spectrum of a network of domain walls is determined. The first ever quantitative constraint for the domain wall surface tension is obtained using a Markov chain Monte Carlo method; an energy scale of domain walls of 0.93 MeV, which is close but below the Zel'dovich bound, is determined.
Contribution of domain wall networks to the CMB power spectrum
Energy Technology Data Exchange (ETDEWEB)
Lazanu, A., E-mail: A.Lazanu@damtp.cam.ac.uk [Centre for Theoretical Cosmology, Department of Applied Mathematics and Theoretical Physics, Wilberforce Road, Cambridge CB3 0WA (United Kingdom); Martins, C.J.A.P., E-mail: Carlos.Martins@astro.up.pt [Centro de Astrofísica, Universidade do Porto, Rua das Estrelas, 4150-762 Porto (Portugal); Instituto de Astrofísica e Ciências do Espaço, CAUP, Rua das Estrelas, 4150-762 Porto (Portugal); Shellard, E.P.S., E-mail: E.P.S.Shellard@damtp.cam.ac.uk [Centre for Theoretical Cosmology, Department of Applied Mathematics and Theoretical Physics, Wilberforce Road, Cambridge CB3 0WA (United Kingdom)
2015-07-30
We use three domain wall simulations from the radiation era to the late-time dark energy domination era based on the PRS algorithm to calculate the energy–momentum tensor components of domain wall networks in an expanding universe. Unequal time correlators in the radiation, matter and cosmological constant epochs are calculated using the scaling regime of each of the simulations. The CMB power spectrum of a network of domain walls is determined. The first ever quantitative constraint for the domain wall surface tension is obtained using a Markov chain Monte Carlo method; an energy scale of domain walls of 0.93 MeV, which is close but below the Zel'dovich bound, is determined.
J-kink domain walls and the DBI action
Eto, Minoru
2015-01-01
We study $J$-kink domain walls in $D=4$ massive $\\mathbb{C}P^1$ sigma model. The domain walls are not static but stationary, since they rotate in an internal $S^1$ space with a frequency $\\omega$ and a momentum ${\\bf k}$ along the domain wall. They are characterized by a conserved current $J_\\mu = (Q,{\\bf J})$, and are classified into magnetic ($J^2 0$) types. Under a natural assumption that a low energy effective action of the domain wall is dual to the $D=4$ DBI action for a membrane, we are lead to a coincidence between the $J$-kink domain wall and the membrane with constant magnetic field $B$ and electric field ${\\bf E}$. We also find that $(Q, {\\bf J}, \\omega, {\\bf k})$ is dual to $(B, {\\bf E}, H, {\\bf D})$ with $H$ and ${\\bf D}$ being a magnetizing field and a displacement field, respectively.
Spin torque and interactions in ferromagnetic semiconductor domain walls
Golovatski, Elizabeth Ann
The motion of domain walls due to the spin torque generated by coherent carrier transport is of considerable interest for the development of spintronic devices. We model the charge and spin transport through domain walls in ferromagnetic semiconductors for various systems. With an appropriate model Hamiltonian for the spin-dependent potential, we calculate wavefunctions inside the domain walls which are then used to calculate transmission and reflection coefficients, which are then in turn used to calculate current and spin torque. Starting with a simple approximation for the change in magnetization inside the domain wall, and ending with a sophisticated transfer matrix method, we model the common pi wall, the less-studied 2pi wall, and a system of two pi walls separated by a variable distance. We uncover an interesting width dependence on the transport properties of the domain wall. 2pi walls in particular, have definitive maximums in resistance and spin torque for certain domain wall widths that can be seen as a function of the spin mistracking in the system---when the spins are either passing straight through the domain wall (narrow walls) or adiabatically following the magnetization (wide walls), the resistance is low as transmission is high. In the intermediate region, there is room for the spins to rotate their magnetization, but not necessarily all the way through a 360 degree rotation, leading to reflection and resistance. We also calculate that there are widths for which the total velocity of a 2pi wall is greater than that of a same-sized pi wall. In the double-wall system, we model how the system reacts to changes in the separation of the domain walls. When the domain walls are far apart, they act as a spin-selective resonant double barrier, with sharp resonance peaks in the transmission profile. Brought closer and closer together, the number and sharpness of the peaks decrease, the spectrum smooths out, and the domain walls brought together have a
Evolution of domain wall networks: the PRS algorithm
Sousa, L
2011-01-01
The Press-Ryden-Spergel (PRS) algorithm is a modification to the field theory equations of motion, parametrized by two parameters ($\\alpha$ and $\\beta$), implemented in numerical simulations of cosmological domain wall networks, in order to ensure a fixed comoving resolution. In this paper we explicitly demonstrate that the PRS algorithm provides the correct domain wall dynamics in $N+1$-dimensional Friedmann-Robertson-Walker (FRW) universes if $\\alpha+\\beta/2=N$, fully validating its use in numerical studies of cosmic domain evolution. We further show that this result is valid for generic thin featureless domain walls, independently of the Lagrangian of the model.
Ballistic rectification of vortex domain wall chirality at nanowire corners
Energy Technology Data Exchange (ETDEWEB)
Omari, K.; Bradley, R. C.; Broomhall, T. J.; Hodges, M. P. P.; Hayward, T. J. [Department of Materials Science and Engineering, University of Sheffield, Sheffield S1 3JD (United Kingdom); Rosamond, M. C.; Linfield, E. H. [School of Electronic and Electrical Engineering, University of Leeds, Leeds LS2 9JT (United Kingdom); Im, M.-Y. [Center for X-Ray Optics, Lawrence Berkeley National Laboratory, Berkeley, California 94720 (United States); Daegu Gyeongbuk Institute of Science and Technology, Daegu 711-873 (Korea, Republic of); Fischer, P. [Materials Sciences Division, Lawrence Berkley National Laboratory, Berkeley, California 94720 (United States); Department of Physics, University of California, Santa Cruz, California 94056 (United States)
2015-11-30
The interactions of vortex domain walls with corners in planar magnetic nanowires are probed using magnetic soft X-ray transmission microscopy. We show that when the domain walls are propagated into sharp corners using applied magnetic fields above a critical value, their chiralities are rectified to either clockwise or anticlockwise circulation depending on whether the corners turn left or right. Single-shot focused magneto-optic Kerr effect measurements are then used to demonstrate how, when combined with modes of domain propagation that conserve vortex chirality, this allows us to dramatically reduce the stochasticity of domain pinning at artificial defect sites. Our results provide a tool for controlling domain wall chirality and pinning behavior both in further experimental studies and in future domain wall-based memory, logic and sensor technologies.
Formation of charged ferroelectric domain walls with controlled periodicity.
Bednyakov, Petr S; Sluka, Tomas; Tagantsev, Alexander K; Damjanovic, Dragan; Setter, Nava
2015-10-30
Charged domain walls in proper ferroelectrics were shown recently to possess metallic-like conductivity. Unlike conventional heterointerfaces, these walls can be displaced inside a dielectric by an electric field, which is of interest for future electronic circuitry. In addition, theory predicts that charged domain walls may influence the electromechanical response of ferroelectrics, with strong enhancement upon increased charged domain wall density. The existence of charged domain walls in proper ferroelectrics is disfavoured by their high formation energy and methods of their preparation in predefined patterns are unknown. Here we develop the theoretical background for the formation of charged domain walls in proper ferroelectrics using energy considerations and outline favourable conditions for their engineering. We experimentally demonstrate, in BaTiO3 single crystals the controlled build-up of high density charged domain wall patterns, down to a spacing of 7 μm with a predominant mixed electronic and ionic screening scenario, hinting to a possible exploitation of charged domain walls in agile electronics and sensing devices.
Effect of microwaves on domain wall motion in thin Ni wires
Hong, Kimin; Giordano, N.
1996-03-01
We report new results on domain wall motion in thin (width and thickness ~ 300 ÅNi wires. The magnetoresistance exhibits discontinuities which we believe are associated with pinning and de-pinning of walls from structural defects, such as variations in the width of the sample. Upon repeated measurement, the de-pinning is found to occur over a narrow range of fields. The distribution of de-pinning fields, P(H), varies with temperature in a manner which suggests that de-pinning occurs via thermal activation at high temperatures, and quantum tunneling at low temperatures, with crossover between these two regimes at T ~ 2 - 6 K. We have also investigated the effect of a 30 GHz microwave field on P(H). In the thermal activation regime, microwaves have no effect on P(H), except through Joule heating. However, in the tunneling regime microwaves cause P(H) to split into several separate peaks. This behavior cannot be explained in terms of Joule heating, but suggests that the energy levels of a domain wall in a pinning well are quantized.
Ultrafast domain wall dynamics in magnetic nanotubes and nanowires
Hertel, R.
2016-12-01
The dynamic properties of magnetic domain walls in nanotubes and in cylindrical nanowires can be significantly different from the well known domain wall dynamics in thin films and in flat thin strips. The main differences are the occurrence of chiral symmetry breaking and, perhaps more importantly, the possibility to obtain magnetic domain walls that are stable against the usual Walker breakdown. This stability enables the magnetic field-driven propagation of the domain walls in nanotubes and nanocylinders at constant velocities which are significantly higher than the usual propagation speeds of the domain walls. Simulations predict that the ultrafast motion of magnetic domain walls at velocities in a range above 1000 m s-1 can lead to the spontaneous excitation of spin waves in a process that is the magnetic analog of the Cherenkov effect. In the case of solid cylindrical wires, the domain wall can contain a micromagnetic point singularity. We discuss the current knowledge on the ultrafast dynamics of such Bloch points, which remains still largely unexplored.
Ferroelectricity of domain walls in rare earth iron garnet films.
Popov, A I; Zvezdin, K A; Gareeva, Z V; Mazhitova, F A; Vakhitov, R M; Yumaguzin, A R; Zvezdin, A K
2016-11-16
In this paper, we report on electric polarization arising in a vicinity of Bloch-like domain walls in rare-earth iron garnet films. The domain walls generate an intrinsic magnetic field that breaks an antiferroelectric structure formed in the garnets due to an exchange interaction between rare earth and iron sublattices. We explore 180° domain walls whose formation is energetically preferable in the films with perpendicular magnetic anisotropy. Magnetic and electric structures of the 180° quasi-Bloch domain walls have been simulated at various relations between system parameters. Singlet, doublet ground states of rare earth ions and strongly anisotropic rare earth Ising ions have been considered. Our results show that electric polarization appears in rare earth garnet films at Bloch domain walls, and the maximum of magnetic inhomogeneity is not always linked to the maximum of electric polarization. A number of factors including the temperature, the state of the rare earth ion and the type of a wall influence magnetically induced electric polarization. We show that the value of polarization can be enhanced by the shrinking of the Bloch domain wall width, decreasing the temperature, and increasing the deviations of magnetization from the Bloch rotation that are regulated by impacts given by magnetic anisotropies of the films.
Ferroelectricity of domain walls in rare earth iron garnet films
Popov, A. I.; Zvezdin, K. A.; Gareeva, Z. V.; Mazhitova, F. A.; Vakhitov, R. M.; Yumaguzin, A. R.; Zvezdin, A. K.
2016-11-01
In this paper, we report on electric polarization arising in a vicinity of Bloch-like domain walls in rare-earth iron garnet films. The domain walls generate an intrinsic magnetic field that breaks an antiferroelectric structure formed in the garnets due to an exchange interaction between rare earth and iron sublattices. We explore 180° domain walls whose formation is energetically preferable in the films with perpendicular magnetic anisotropy. Magnetic and electric structures of the 180° quasi-Bloch domain walls have been simulated at various relations between system parameters. Singlet, doublet ground states of rare earth ions and strongly anisotropic rare earth Ising ions have been considered. Our results show that electric polarization appears in rare earth garnet films at Bloch domain walls, and the maximum of magnetic inhomogeneity is not always linked to the maximum of electric polarization. A number of factors including the temperature, the state of the rare earth ion and the type of a wall influence magnetically induced electric polarization. We show that the value of polarization can be enhanced by the shrinking of the Bloch domain wall width, decreasing the temperature, and increasing the deviations of magnetization from the Bloch rotation that are regulated by impacts given by magnetic anisotropies of the films.
Van de Wiele, Ben; Leliaert, Jonathan; Franke, Kévin J. A.; van Dijken, Sebastiaan
2016-03-01
Strong coupling of magnetic domain walls onto straight ferroelastic boundaries of a ferroelectric layer enables full and reversible electric-field control of magnetic domain wall motion. In this paper, the dynamics of this new driving mechanism is analyzed using micromagnetic simulations. We show that transverse domain walls with a near-180° spin structure are stabilized in magnetic nanowires and that electric fields can move these walls with high velocities. Above a critical velocity, which depends on material parameters, nanowire geometry and the direction of domain wall motion, the magnetic domain walls depin abruptly from the ferroelastic boundaries. Depinning evolves either smoothly or via the emission and annihilation of a vortex or antivortex core (Walker breakdown). In both cases, the magnetic domain wall slows down after depinning in an oscillatory fashion and eventually comes to a halt. The simulations provide design rules for hybrid ferromagnetic-ferroelectric domain-wall-based devices and indicate that material disorder and structural imperfections only influence Walker-breakdown-like depinning at high domain wall velocities.
Domain wall stability in ferroelectrics with space charges
Energy Technology Data Exchange (ETDEWEB)
Zuo, Yinan, E-mail: zuo@mfm.tu-darmstadt.de; Genenko, Yuri A.; Klein, Andreas; Stein, Peter; Xu, Baixiang [Institute of Materials Science, Technische Universität Darmstadt, D-64287 Darmstadt (Germany)
2014-02-28
Significant effect of semiconductor properties on domain configurations in ferroelectrics is demonstrated, especially in the case of doped materials. Phase field simulations are performed for ferroelectrics with space charges due to donors and electronic charge carriers. The free charges introduced thereby can act as a source for charge compensation at domain walls with uncompensated polarization bound charges. Results indicate that the equilibrium position of a domain wall with respect to its rotation in a head-to-head or a tail-to-tail domain configuration depends on the charge defect concentration and the Fermi level position.
Scalar triplet on a domain wall: an exact solution
Gani, Vakhid A.; Lizunova, Mariya A.; Radomskiy, Roman V.
2016-04-01
We study a model with a real scalar Higgs field and a scalar triplet field that allows existence of a topological defect — a domain wall. The wall breaks the global O(3) symmetry of the model, which gives rise to non-Abelian orientational degrees of freedom. We found an exact analytic solution that describes a domain wall with a localized configuration of the triplet field on it. This solution enables one to calculate contributions to the action from the orientational and translational degrees of freedom of the triplet field. We also study the linear stability of the domain wall with the triplet field switched off. We obtain that degrees of freedom localized on the wall can appear or do not appear depending on the parameters of the model.
Highly Efficient Domain Walls Injection in Perpendicular Magnetic Anisotropy Nanowire.
Zhang, S F; Gan, W L; Kwon, J; Luo, F L; Lim, G J; Wang, J B; Lew, W S
2016-04-21
Electrical injection of magnetic domain walls in perpendicular magnetic anisotropy nanowire is crucial for data bit writing in domain wall-based magnetic memory and logic devices. Conventionally, the current pulse required to nucleate a domain wall is approximately ~10(12) A/m(2). Here, we demonstrate an energy efficient structure to inject domain walls. Under an applied electric potential, our proposed Π-shaped stripline generates a highly concentrated current distribution. This creates a highly localized magnetic field that quickly initiates the nucleation of a magnetic domain. The formation and motion of the resulting domain walls can then be electrically detected by means of Ta Hall bars across the nanowire. Our measurements show that the Π-shaped stripline can deterministically write a magnetic data bit in 15 ns even with a relatively low current density of 5.34 × 10(11) A/m(2). Micromagnetic simulations reveal the evolution of the domain nucleation - first, by the formation of a pair of magnetic bubbles, then followed by their rapid expansion into a single domain. Finally, we also demonstrate experimentally that our injection geometry can perform bit writing using only about 30% of the electrical energy as compared to a conventional injection line.
Highly Efficient Domain Walls Injection in Perpendicular Magnetic Anisotropy Nanowire
Zhang, S. F.; Gan, W. L.; Kwon, J.; Luo, F. L.; Lim, G. J.; Wang, J. B.; Lew, W. S.
2016-04-01
Electrical injection of magnetic domain walls in perpendicular magnetic anisotropy nanowire is crucial for data bit writing in domain wall-based magnetic memory and logic devices. Conventionally, the current pulse required to nucleate a domain wall is approximately ~1012 A/m2. Here, we demonstrate an energy efficient structure to inject domain walls. Under an applied electric potential, our proposed Π-shaped stripline generates a highly concentrated current distribution. This creates a highly localized magnetic field that quickly initiates the nucleation of a magnetic domain. The formation and motion of the resulting domain walls can then be electrically detected by means of Ta Hall bars across the nanowire. Our measurements show that the Π-shaped stripline can deterministically write a magnetic data bit in 15 ns even with a relatively low current density of 5.34 × 1011 A/m2. Micromagnetic simulations reveal the evolution of the domain nucleation – first, by the formation of a pair of magnetic bubbles, then followed by their rapid expansion into a single domain. Finally, we also demonstrate experimentally that our injection geometry can perform bit writing using only about 30% of the electrical energy as compared to a conventional injection line.
Simulating the symmetron: domain walls and symmetry-restoring impurities
Pearson, Jonathan A
2014-01-01
In this paper we study the dynamics of relativistic domain walls in the presence of static symmetry-restoring impurities. The field theory is precisely the same as what is known to cosmologists as the "symmetron model", whereby the usual $\\mathbb{Z}_2$ symmetry breaking potential is appended with a space-varying mass-term (the space-variation is set by the profile of the impurity, which we take to be a "tanh"-function). After presenting the outcomes of a suite of different numerical experiments we have three main results: (1) domain walls pin to impurities, (2) domain wall necklaces can be energetically preferred configurations, and (3) impurities significantly modifies the usual ${N}_{\\rm dw}\\propto t^{-1}$ scaling law for random networks of domain walls.
Skyrmion and Baby Skyrmion Formation from Domain Walls
Winyard, Thomas
2015-01-01
We numerically simulate the formation of $(2+1)$-dimensional baby Skyrmions and $(3+1)$-dimensional $SU(2)$ Skyrmions from domain wall collisions. It has been suggested that Skyrmion, anti-Skyrmion pairs can be produced from the interaction of two domain walls. This is confirmed, however it is also demonstrated that the process can require quite precise conditions. An alternative, more stable, formation process is proposed as the interaction of more than two segments of domain wall. This is simulated, requiring far less constraints on the initial conditions used. Finally domain wall networks are considered, demonstrating how Skyrmions may be produced in a complex dynamical system. We show that the local topological charge configurations, formed within the system, are countered by opposite winding on the boundary of the system to conserve topological charge.
Axion cosmology with long-lived domain walls
Hiramatsu, Takashi; Saikawa, Ken'ichi; Sekiguchi, Toyokazu
2012-01-01
We investigate the cosmological constraints on axion models where the domain wall number is greater than one. In these models, multiple domain walls attached to strings are formed, and they survive for a long time. Their annihilation occurs due to the effects of explicit symmetry breaking term which might be raised by Planck-scale physics. We perform three-dimensional lattice simulations and compute the spectra of axions and gravitational waves produced by long-lived domain walls. Using the numerical results, we estimated relic density of axions and gravitational waves. We find that the existence of long-lived domain walls leads to the overproduction of cold dark matter axions, while the density of gravitational waves is too small to observe at the present time. Combining the results with other observational constraints, we find that the whole parameter region of models are excluded unless an unacceptable fine-tuning exists.
Thermal variations of domain wall thickness and number of domains in magnetic rectangular grains
Xu, Song; Merrill, Ronald T.
1990-12-01
Equilibrium domain wall thickness and number of domains in rectangular magnetic grains are determined by using a modified Amar model. It is shown that domain structure, particularly domain wall thickness, in a magnetized grain depends strongly on grain shape and orientation. These dependencies are attributed to the existence of two competing self-magnetostatic interactions, one from the ends of the grain and the other from the sides. One of the consequences of this is that the thermal variation of domain wall thickness in an elongated grain is greater (smaller) than predicted by classical theory when the grain is magnetized along the shortest (longest) dimension. For magnetite, classical theory provides a good approximation in predicting both domain wall thickness and number of domains in equal-dimensional grains larger than about 4 μm.
Enhanced controllability of domain-wall pinning by asymmetric control of domain-wall injection.
Ahn, Sung-Min; Moon, Kyoung-Woong
2013-03-15
We investigate a control scheme for enhancing the controllability of domain-wall (DW) pinning on ferromagnetic devices using an interaction between magnetic charges distributed on a nanobar and at a notch, respectively. The scheme is realized at an artificial notch with a nanobar vertical to it on Permalloy nanowires with an asymmetrical pad. Injection fields for injecting the DWs from the asymmetrical pad to the nanowire show an asymmetrical dependence on the saturation angle for initializing the magnetization of the nanowire, and the injected DWs are pinned by the notch with the nanobar vertical to it. We have found that the landscape of the pinning potential energy experienced by the DWs depends on the magnetized direction of the nanobar and that its level is shifted by the injection field, leading to an increase or decrease in the depinning field with respect to the saturation angle. This is consistent with our estimation based on micromagnetic simulation.
New confining force solution of QCD axion domain wall problem
Barr, S. M.; Kim, Jihn E.
2014-01-01
The serious cosmological problems created by the axion-string/axion-domain-wall system in standard axion models are alleviated by positing the existence of a new confining force. The instantons of this force can generate an axion potential that erases the axion strings long before QCD effects become important, thus preventing QCD-generated axion walls from ever appearing. Axion walls generated by the new confining force would decay so early as not to contribute significantly to the energy in ...
Decaying Domain Walls in an Extended Gravity Model and Cosmology
Shiraishi, Kiyoshi
2013-01-01
We investigate cosmological consequences of an extended gravity model which belongs to the same class studied by Accetta and Steinhardt in an extended inflationary scenario. But we do not worry about inflation in our model; instead, we focus on a topological object formed during cosmological phase transitions. Although domain walls appear during first-order phase transitions such as QCD transition, they decay at the end of the phase transition. Therefore the "domain wall problem" does not exist in the suitable range of pameters and, on the contrary, the "fragments" of walls may become seeds of dark matter. A possible connection to "oscillating universe" model offered by Morikawa et al. is also discussed.
Thick domain wall spacetimes with and without reflection symmetry
Melfo, A; Skirzewski, A; Melfo, Alejandra; Pantoja, Nelson; Skirzewski, Aureliano
2003-01-01
We show that the spacetimes of domain wall solutions to the coupled Einstein-scalar field equations with a given scalar field potential fall into two classes, depending on whether or not reflection symmetry on the wall is imposed. Solutions with reflection symmetry are dynamic, while the asymmetric ones are static. Asymmetric walls are asymptotically flat on one side and reduce to the Taub spacetime on the other. Examples of asymmetric thick walls in D-dimensional spacetimes are given, and results on the thin-wall limit of the dynamic, symmetric walls are extended to the asymmetric case. The particular case of symmetric, static spacetimes is considered and a new family of solutions, including previously known BPS walls, is presented.
Quantum Dynamics of Spin Wave Propagation through Domain Walls
Yuan, S.; Raedt, H. De; Miyashita, S.
2006-01-01
Through numerical solution of the time-dependent Schrödinger equation, we demonstrate that magnetic chains with uniaxial anisotropy support stable structures, separating ferromagnetic domains of opposite magnetization. These structures, domain walls in a quantum system, are shown to remain stable if
Nonlinear dynamics of domain walls with cross-ties
Energy Technology Data Exchange (ETDEWEB)
Dubovik, M. N., E-mail: dubovik@imp.uran.ru [Russian Academy of Sciences, Institute of Metal Physics, Ural Branch (Russian Federation); Zverev, V. V. [Ural Federal University (Russian Federation); Filippov, B. N. [Russian Academy of Sciences, Institute of Metal Physics, Ural Branch (Russian Federation)
2016-07-15
The dynamic behavior of a domain wall with cross-ties is analyzed on the basis of micromagnetic simulation with exact allowance for all main (exchange, magnetoanisotropic, and magnetostatic) interactions in thin magnetically uniaxial ferromagnetic films with planar anisotropy. It is found that the peculiarities of motion of such domain walls are closely related to the behavior of topological defects in the magnetization distribution (generation, motion, and annihilation of vortex–antivortex pairs on the film surface and Bloch points). We observe three different regimes of motion (stationary, periodic, and turbulent regimes), each of which is realized in a certain range of fields oriented along the easy magnetization axis. It is shown that the experimentally observed dynamic bends of the walls with cross-ties are determined by the type of motion of vortices and antivortices. The velocities of domain walls in different regimes are calculated, and the dynamic configurations of the magnetization and existing dynamic transitions between them are investigated.
Nonlinear dynamics of domain walls with cross-ties
Dubovik, M. N.; Zverev, V. V.; Filippov, B. N.
2016-07-01
The dynamic behavior of a domain wall with cross-ties is analyzed on the basis of micromagnetic simulation with exact allowance for all main (exchange, magnetoanisotropic, and magnetostatic) interactions in thin magnetically uniaxial ferromagnetic films with planar anisotropy. It is found that the peculiarities of motion of such domain walls are closely related to the behavior of topological defects in the magnetization distribution (generation, motion, and annihilation of vortex-antivortex pairs on the film surface and Bloch points). We observe three different regimes of motion (stationary, periodic, and turbulent regimes), each of which is realized in a certain range of fields oriented along the easy magnetization axis. It is shown that the experimentally observed dynamic bends of the walls with cross-ties are determined by the type of motion of vortices and antivortices. The velocities of domain walls in different regimes are calculated, and the dynamic configurations of the magnetization and existing dynamic transitions between them are investigated.
Magnetoelastic contribution in domain wall propagation of micrometric wires.
Zhukov, A; Blanco, J M; Ipatov, M; Zhukova, V
2012-09-01
We report on studies of domain wall propagation of magnetically-bistable Fe-Co-rich microwires paying attention on the effect of applied and internal stresses. We measured magnetic domain propagation in various magnetic Fe-Co-rich amorphous microwires with metallic nucleus diameters (from 2.8 microm to 18 microm) using Sixtus Tonks-like experiments. We found that application of applied stresses and increasing of internal stresses result in decreasing of domain wall (DW) velocity. We assume that in order to achieve higher DW propagation velocity at the same magnetic field and enhanced DW mobility, special attention should be paid to the decrease of magnetoelastic energy.
Evolution of thick domain walls in de Sitter universe
Dolgov, A D; Rudenko, A S
2016-01-01
We consider thick domain walls in a de Sitter universe following paper by Basu and Vilenkin. However, we are interested not only in stationary solutions found therein, but also investigate the general case of domain wall evolution with time. When the wall thickness parameter, $\\delta_0$, is smaller than $H^{-1}/\\sqrt{2}$, where $H$ is the Hubble parameter in de Sitter space-time, then the stationary solutions exist, and initial field configurations tend with time to the stationary ones. However, there are no stationary solutions for $\\delta_0 \\geq H^{-1}/\\sqrt{2}$. We have calculated numerically the rate of the wall expansion in this case and have found that the width of the wall grows exponentially fast for $\\delta_0 \\gg H^{-1}$. An explanation for the critical value $\\delta_{0c} = H^{-1}/\\sqrt{2}$ is also proposed.
Evolution of thick domain walls in de Sitter universe
Dolgov, A. D.; Godunov, S. I.; Rudenko, A. S.
2016-10-01
We consider thick domain walls in a de Sitter universe following paper by Basu and Vilenkin. However, we are interested not only in stationary solutions found therein, but also investigate the general case of domain wall evolution with time. When the wall thickness parameter, δ0, is smaller than H‑1/√2, where H is the Hubble parameter in de Sitter space-time, then the stationary solutions exist, and initial field configurations tend with time to the stationary ones. However, there are no stationary solutions for δ0 >= H‑1/√2. We have calculated numerically the rate of the wall expansion in this case and have found that the width of the wall grows exponentially fast for δ0 gg H‑1. An explanation for the critical value δ0c = H‑1/√2 is also proposed.
Domain and wall structures in films with helical magnetization profile
Energy Technology Data Exchange (ETDEWEB)
Dubuget, Vincent [Laboratoire d' Electrodynamique des Materiaux Avances, Universite Francois Rabelais, CNRS UMR 6157, Parc de Grandmont, F-37200 Tours (France); CEA, DAM, Le Ripault, F-37260 Monts (France); Thiaville, Andre [Laboratoire de Physique des Solides, Universite Paris-Sud, CNRS UMR 8502, Bat. 510, F-91405 Orsay (France); Adenot-Engelvin, Anne-Lise, E-mail: anne-lise.adenot-engelvin@cea.f [CEA, DAM, Le Ripault, F-37260 Monts (France); Duverger, Francois; Dubourg, Sebastien [CEA, DAM, Le Ripault, F-37260 Monts (France)
2011-06-15
We study soft magnetic bilayers having orthogonal, in-plane easy axes. The layers are thicker than the Bloch wall width linked to the anisotropy, so that a helical magnetization with a large angle exists across the sample thickness. The magnetic domains structure has been investigated at both sample surfaces, using magneto-optical microscopy. The domain structure is found to be similar to that of double films with biquadratic coupling. Two kinds of domain walls are identified, namely with a 90{sup o} and 180{sup o} rotation of the average magnetization. The detailed structure and energy of these walls are studied by micromagnetic calculations. - Research highlights: This paper is devoted to the peculiar domain structure resulting from an anisotropy distribution in the thickness of the sample, realized through specific elaboration conditions. The helical magnetization profile obtained leads to a complex dynamic behaviour described and modelled in Phys.Rev. B 80, 134412 (published in October 2009) which has been already cited three times. This paper sheds light on of the demagnetized state of such samples: a variety of domains structure has been observed by Kerr microscopy, under various saturation fields. The most striking conclusion is driven by the analysis of the magnetization process which implies the co-existence of two types of domain walls in the sample, with four possible directions for the mean magnetization. The magnetization profile of the two walls has been confirmed by numerical simulation.
Magnetic domain wall conduits for single cell applications
DEFF Research Database (Denmark)
Donolato, Marco; Torti, A.; Kostesha, Natalie;
2011-01-01
The ability to trap, manipulate and release single cells on a surface is important both for fundamental studies of cellular processes and for the development of novel lab-on-chip miniaturized tools for biological and medical applications. In this paper we demonstrate how magnetic domain walls...... generated in micro- and nano-structures fabricated on a chip surface can be used to handle single yeast cells labeled with magnetic beads. In detail, first we show that the proposed approach maintains the microorganism viable, as proven by monitoring the division of labeled yeast cells trapped by domain...... walls over 16 hours. Moreover, we demonstrate the controlled transport and release of individual yeast cells via displacement and annihilation of individual domain walls in micro- and nano-sized magnetic structures. These results pave the way to the implementation of magnetic devices based on domain...
Domain walls and ferroelectric reversal in corundum derivatives
Ye, Meng; Vanderbilt, David
2017-01-01
Domain walls are the topological defects that mediate polarization reversal in ferroelectrics, and they may exhibit quite different geometric and electronic structures compared to the bulk. Therefore, a detailed atomic-scale understanding of the static and dynamic properties of domain walls is of pressing interest. In this work, we use first-principles methods to study the structures of 180∘ domain walls, both in their relaxed state and along the ferroelectric reversal pathway, in ferroelectrics belonging to the family of corundum derivatives. Our calculations predict their orientation, formation energy, and migration energy and also identify important couplings between polarization, magnetization, and chirality at the domain walls. Finally, we point out a strong empirical correlation between the height of the domain-wall-mediated polarization reversal barrier and the local bonding environment of the mobile A cations as measured by bond-valence sums. Our results thus provide both theoretical and empirical guidance for future searches for ferroelectric candidates in materials of the corundum derivative family.
Voltage-controlled domain wall traps in ferromagnetic nanowires
Bauer, Uwe; Emori, Satoru; Beach, Geoffrey S. D.
2013-06-01
Electrical control of magnetism has the potential to bring about revolutionary new spintronic devices, many of which rely on efficient manipulation of magnetic domain walls in ferromagnetic nanowires. Recently, it has been shown that voltage-induced charge accumulation at a metal-oxide interface can influence domain wall motion in ultrathin metallic ferromagnets, but the effects have been relatively modest and limited to the slow, thermally activated regime. Here we show that a voltage can generate non-volatile switching of magnetic properties at the nanoscale by modulating interfacial chemistry rather than charge density. Using a solid-state ionic conductor as a gate dielectric, we generate unprecedentedly strong voltage-controlled domain wall traps that function as non-volatile, electrically programmable and switchable pinning sites. Pinning strengths of at least 650 Oe can be readily achieved, enough to bring to a standstill domain walls travelling at speeds of at least ~20 m s-1. We exploit this new magneto-ionic effect to demonstrate a prototype non-volatile memory device in which voltage-controlled domain wall traps facilitate electrical bit selection in a magnetic nanowire register.
Localization of vector field on dynamical domain wall
Directory of Open Access Journals (Sweden)
Masafumi Higuchi
2017-03-01
Full Text Available In the previous works (arXiv:1202.5375 and arXiv:1402.1346, the dynamical domain wall, where the four dimensional FRW universe is embedded in the five dimensional space–time, has been realized by using two scalar fields. In this paper, we consider the localization of vector field in three formulations. The first formulation was investigated in the previous paper (arXiv:1510.01099 for the U(1 gauge field. In the second formulation, we investigate the Dvali–Shifman mechanism (arXiv:hep-th/9612128, where the non-abelian gauge field is confined in the bulk but the gauge symmetry is spontaneously broken on the domain wall. In the third formulation, we investigate the Kaluza–Klein modes coming from the five dimensional graviton. In the Randall–Sundrum model, the graviton was localized on the brane. We show that the (5,μ components (μ=0,1,2,3 of the graviton are also localized on the domain wall and can be regarded as the vector field on the domain wall. There are, however, some corrections coming from the bulk extra dimension if the domain wall universe is expanding.
Induced motion of domain walls in multiferroics with quadratic interaction
Energy Technology Data Exchange (ETDEWEB)
Gerasimchuk, Victor S., E-mail: viktor.gera@gmail.com [National Technical University of Ukraine “Kyiv Polytechnic Institute”, Peremohy Avenue 37, 03056 Kiev (Ukraine); Shitov, Anatoliy A., E-mail: shitov@mail.ru [Donbass National Academy of Civil Engineering, Derzhavina Street 2, 86123 Makeevka, Donetsk Region (Ukraine)
2013-10-15
We theoretically study the dynamics of 180-degree domain wall of the ab-type in magnetic materials with quadratic magnetoelectric interaction in external alternating magnetic and electric fields. The features of the oscillatory and translational motions of the domain walls and stripe structures depending on the parameters of external fields and characteristics of the multiferroics are discussed. The possibility of the domain walls drift in a purely electric field is established. - Highlights: • We study DW and stripe DS in multiferroics with quadratic magnetoelectric interaction. • We build up the theory of oscillatory and translational (drift) DW and DS motion. • DW motion can be caused by crossed alternating electric and magnetic fields. • DW motion can be caused by alternating “pure” electric field. • DW drift velocity is formed by the AFM and Dzyaloshinskii interaction terms.
Domain walls and gravitational waves in the Standard Model
Krajewski, Tomasz; Lalak, Zygmunt; Lewicki, Marek; Olszewski, Paweł
2016-12-01
We study domain walls which can be created in the Standard Model under the assumption that it is valid up to very high energy scales. We focus on domain walls interpolating between the physical electroweak vacuum and the global minimum appearing at very high field strengths. The creation of the network which ends up in the electroweak vacuum percolating through the Universe is not as difficult to obtain as one may expect, although it requires certain tuning of initial conditions. Our numerical simulations confirm that such domain walls would swiftly decay and thus cannot dominate the Universe. We discuss the possibility of detection of gravitational waves produced in this scenario. We have found that for the standard cosmology the energy density of these gravitational waves is too small to be observed in present and planned detectors.
Domain walls and gravitational waves in the Standard Model
Krajewski, Tomasz; Lewicki, Marek; Olszewski, Paweł
2016-01-01
We study domain walls which can be created in the Standard Model under the assumption that it is valid up to very high energy scales. We focus on domain walls interpolating between the physical electroweak vacuum and the global minimum appearing at very high field strengths. The creation of the network which ends up in the electroweak vacuum percolating through the Universe is not as difficult to obtain as one may expect, although it requires certain tuning of initial conditions. Our numerical simulations confirm that such domain walls would swiftly decay and thus cannot dominate the Universe. We discuss the possibility of detection of gravitational waves produced in this scenario. We have found that for the standard cosmology the energy density of these gravitational waves is too small to be observed in present and planned detectors.
A review of gravitational waves from cosmic domain walls
Energy Technology Data Exchange (ETDEWEB)
Saikawa, Ken' ichi
2017-03-15
In this contribution, we discuss the cosmological scenario where unstable domain walls are formed in the early universe and their late-time annihilation produces a significant amount of gravitational waves. After describing cosmological constraints on long-lived domain walls, we estimate the typical amplitude and frequency of gravitational waves observed today. We also review possible extensions of the standard model of particle physics that predict the formation of unstable domain walls and can be probed by observation of relic gravitational waves. It is shown that recent results of pulser timing arrays and direct detection experiments partially exclude the relevant parameter space, and that a much wider parameter space can be covered by the next generation of gravitational wave observatories.
Critical behavior of spherically symmetric domain wall collapse
Ikeda, Taishi
2016-01-01
Critical collapse of a spherically symmetric domain wall is investigated. The domain wall is made of a minimally coupled scalar field with a double well potential. We consider a sequence of the initial data which describe a momentarily static domain wall characterized by its initial radius. The time evolution is performed by a full general relativistic numerical code for spherically symmetric systems. In this paper, we use the maximal slice gauge condition, in which spacelike time slices may penetrate the black hole horizon differently from other widely used procedures. In this paper, we consider two specific shapes of the double well potential, and observe the Type II critical behavior in both cases. The mass scaling, sub-critical curvature scaling, and those fine structures are confirmed. The index of the scaling behavior agrees with the massless scalar case.
Submicrometric 2D ratchet effect in magnetic domain wall motion
Energy Technology Data Exchange (ETDEWEB)
Castán-Guerrero, C., E-mail: ccastan@unizar.es [Instituto de Ciencia de Materiales de Aragón (ICMA), CSIC – Universidad de Zaragoza, E-50009 Zaragoza (Spain); Dpto. de Física de la Materia Condensada, Universidad de Zaragoza, E-50009 Zaragoza (Spain); Herrero-Albillos, J. [Fundación ARAID, E-50004 Zaragoza (Spain); Centro Universitario de la Defensa, E-50090 Zaragoza (Spain); Instituto de Ciencia de Materiales de Aragón (ICMA), CSIC – Universidad de Zaragoza, E-50009 Zaragoza (Spain); Sesé, J. [Instituto de Nanociencia de Aragón, Laboratorio de Microscopías Avanzadas, Universidad de Zaragoza, E-50018 Zaragoza (Spain); Dpto. de Física de la Materia Condensada, Universidad de Zaragoza, E-50009 Zaragoza (Spain); Bartolomé, J.; Bartolomé, F. [Instituto de Ciencia de Materiales de Aragón (ICMA), CSIC – Universidad de Zaragoza, E-50009 Zaragoza (Spain); Dpto. de Física de la Materia Condensada, Universidad de Zaragoza, E-50009 Zaragoza (Spain); Hierro-Rodriguez, A.; Valdés-Bango, F.; Martín, J.I.; Alameda, J.M. [Dpto. Física, Universidad de Oviedo, Asturias (Spain); CINN (CSIC – Universidad de Oviedo – Principado de Asturias), Asturias (Spain); García, L.M. [Instituto de Ciencia de Materiales de Aragón (ICMA), CSIC – Universidad de Zaragoza, E-50009 Zaragoza (Spain); Dpto. de Física de la Materia Condensada, Universidad de Zaragoza, E-50009 Zaragoza (Spain)
2014-12-15
Strips containing arrays of submicrometric triangular antidots with a 2D square periodicity have been fabricated by electron beam lithography. A clear ratchet effect of 180° domain wall motion under a varying applied field parallel to the walls has been observed. The direction is determined by the direction of the triangle vertices. In contrast, no ratchet effect is observed when the antidot array is constituted by symmetric rhomb-shaped antidots.
Light wave propagation through a dilaton-Maxwell domain wall
Morris, J R
2015-01-01
We consider the propagation of electromagnetic waves through a dilaton-Maxwell domain wall of the type introduced by Gibbons and Wells [G.W. Gibbons and C.G. Wells, Class. Quant. Grav. 11, 2499-2506 (1994)]. It is found that if such a wall exists within our observable universe, it would be absurdly thick, or else have a magnetic field in its core which is much stronger than observed intergalactic fields. We conclude that it is highly improbable that any such wall is physically realized.
Low energy electron imaging of domains and domain walls in magnesium-doped lithium niobate
Nataf, G. F.; Grysan, P.; Guennou, M.; Kreisel, J.; Martinotti, D.; Rountree, C. L.; Mathieu, C.; Barrett, N.
2016-09-01
The understanding of domain structures, specifically domain walls, currently attracts a significant attention in the field of (multi)-ferroic materials. In this article, we analyze contrast formation in full field electron microscopy applied to domains and domain walls in the uniaxial ferroelectric lithium niobate, which presents a large 3.8 eV band gap and for which conductive domain walls have been reported. We show that the transition from Mirror Electron Microscopy (MEM - electrons reflected) to Low Energy Electron Microscopy (LEEM - electrons backscattered) gives rise to a robust contrast between domains with upwards (Pup) and downwards (Pdown) polarization, and provides a measure of the difference in surface potential between the domains. We demonstrate that out-of-focus conditions of imaging produce contrast inversion, due to image distortion induced by charged surfaces, and also carry information on the polarization direction in the domains. Finally, we show that the intensity profile at domain walls provides experimental evidence for a local stray, lateral electric field.
Low energy electron imaging of domains and domain walls in magnesium-doped lithium niobate
Nataf, G. F.; Grysan, P.; Guennou, M.; Kreisel, J.; Martinotti, D.; Rountree, C. L.; Mathieu, C.; Barrett, N.
2016-01-01
The understanding of domain structures, specifically domain walls, currently attracts a significant attention in the field of (multi)-ferroic materials. In this article, we analyze contrast formation in full field electron microscopy applied to domains and domain walls in the uniaxial ferroelectric lithium niobate, which presents a large 3.8 eV band gap and for which conductive domain walls have been reported. We show that the transition from Mirror Electron Microscopy (MEM – electrons reflected) to Low Energy Electron Microscopy (LEEM – electrons backscattered) gives rise to a robust contrast between domains with upwards (Pup) and downwards (Pdown) polarization, and provides a measure of the difference in surface potential between the domains. We demonstrate that out-of-focus conditions of imaging produce contrast inversion, due to image distortion induced by charged surfaces, and also carry information on the polarization direction in the domains. Finally, we show that the intensity profile at domain walls provides experimental evidence for a local stray, lateral electric field. PMID:27608605
Magnetic domain wall energy in Ni/Co superlattices
Energy Technology Data Exchange (ETDEWEB)
Toyoki, Kentaro; Nishimura, Takashi; Harimoto, Shotaro; Shiratsuchi, Yu, E-mail: shiratsuchi@mat.eng.osaka-u.ac.jp; Nakatani, Ryoichi
2014-12-15
The magnetic domain wall energy density σ{sub W} of a Ni/Co superlattice possessing perpendicular magnetic anisotropy was determined using the magnetic domain theory derived by Kooy and Enz (1960). To determine σ{sub W}, we obtained the saturation magnetization, magnetic domain period, and perpendicular magnetic anisotropy energy by individual measurements. Using the magnetic domain period and the ferromagnetic layer thickness, we first determined the dipolar length. The estimated dipolar length was about 15–25 nm, which is in good agreement with the change in the magnetization curve with the ferromagnetic layer thickness. By using the dipolar length and saturation magnetization, the σ{sub W} was calculated to be 4–7 erg/cm{sup 2}. - Highlights: • Magnetic domain wall energy of a Ni/Co superlattice was determined experimentally. • The magnetic domain wall energy was estimated to be 4–8 erg/cm{sup 2}. • Using estimated value, the magnetization curves were reproduced well. • The estimated value is reasonable compared with the other ferromagnetic materials.
Spin pumping by a field-driven domain wall
Duine, R.A.
2008-01-01
We present the theory of spin pumping by a field-driven domain wall for the situation that spin is not fully conserved. We calculate the pumped current in a metallic ferromagnet to first order in the time derivative of the magnetization direction. Irrespective of the microscopic details, the result
Subatomic movements of a domain wall in the Peierls potential
Novoselov, K. S.; Geim, A. K.; Dubonos, S. V.; Hill, E. W.; Grigorieva, I. V.
2003-12-01
The discrete nature of crystal lattices plays a role in virtually every material property. But it is only when the size of entities hosted by a crystal becomes comparable to the lattice period-as occurs for dislocations, vortices in superconductors and domain walls-that this discreteness is manifest explicitly. The associated phenomena are usually described in terms of a background Peierls `atomic washboard' energy potential, which was first introduced for the case of dislocation motion in the 1940s. This concept has subsequently been invoked in many situations to describe certain features in the bulk behaviour of materials, but has to date eluded direct detection and experimental scrutiny at a microscopic level. Here we report observations of the motion of a single magnetic domain wall at the scale of the individual peaks and troughs of the atomic energy landscape. Our experiments reveal that domain walls can become trapped between crystalline planes, and that they propagate by distinct jumps that match the lattice periodicity. The jumps between valleys are found to involve unusual dynamics that shed light on the microscopic processes underlying domain-wall propagation. Such observations offer a means for probing experimentally the physics of topological defects in discrete lattices-a field rich in phenomena that have been subject to extensive theoretical study.
Localization of Vector Field on Dynamical Domain Wall
Higuchi, Masafumi
2016-01-01
In the previous works (arXiv:1202.5375 and 1402.1346), the dynamical domain wall, where the four dimensional FRW universe is embedded in the five imensional space-time, has been realized by using two scalar fields. In this paper, we consider the localization of vector field in three formulations. The first formulation was investigated in the previous paper (arXiv:1510.01099) for the $U(1)$ gauge field. In the second formulation, we investigate the Dvali-Shifman mechanism (hep-th/9612128), where the non-abelian gauge field is confined in the bulk but the gauge symmetry is spontaneously broken on the domain wall. In the third formulation, we investigate the Kaluza-Klein modes coming from the five dimensional graviton. In the Randall-Sundrum model, the graviton was localized on the brane. We show that the $(5,\\mu)$ components $\\left(\\mu=0,1,2,3\\right)$ of the graviton are also localized on the domain wall and can be regarded as the vector field on the domain wall. There are, however, some corrections coming from...
Magnetic domain wall motion triggered by electric field
Energy Technology Data Exchange (ETDEWEB)
Pyatakov, A P; Sergeev, A S; Sechin, D A; Meshkov, G A; Nikolaeva, E P; Nikolaev, A V; Logginov, A S [Physics Department, M.V. Lomonosov Moscow State University, Leninskie gory, Moscow, 119296 (Russian Federation); Zvezdin, A K, E-mail: pyatakov@phys.msu.r [A.M. Prokhorov General Physics Institute, 38, Vavilova st., Moscow, 119991 (Russian Federation)
2010-01-01
We propose the new approach to the problem of electrically controlled magnetic state: the electric field driven domain wall motion. The effect is demonstrated in iron garnet films in ambient conditions. The theoretical model based on inhomogenous magnetoelectric interaction provides with the necessary criteria of the effect and the way to maximize it.
On domain wall boundary conditions for the XXZ spin Hamiltonian
DEFF Research Database (Denmark)
Orlando, Domenico; Reffert, Susanne; Reshetikhin, Nicolai
In this note, we derive the spectrum of the infinite quantum XXZ spin chain with domain wall boundary conditions. The eigenstates are constructed as limits of Bethe states for the finite XXZ spin chain with quantum sl(2) invariant boundary conditions....
Casimir densities for parallel plate in the Domain Wall background
Setare, M R
2003-01-01
The Casimir forces on two parallel plates in conformally flat domain wall background due to conformally coupled massless scalar field satisfying mixed boundary conditions on the plates is investigated. In the general case of mixed boundary conditions formulae are derived for the vacuum expectation values of the energy-momentum tensor and vacuum forces acting on boundaries.
Petitjean, Cyril; Luc, David; Waintal, Xavier
2012-09-14
Spins transverse to the magnetization of a ferromagnet only survive over a short distance. We develop a drift-diffusion approach that captures the main features of transverse spin effects in systems with arbitrary spin textures (e.g., vortices and domain walls) and generalizes the Valet-Fert theory. In addition to the standard characteristic lengths (mean free path for majority and minority electrons, and spin diffusion length), the theory introduces two length scales, the transverse spin coherence length ℓ(⊥) and the (Larmor) spin precession length ℓ(L). We show how ℓ(L) and ℓ(⊥) can be extracted from ab initio calculations or measured with giant magnetoresistance experiments. In long (adiabatic) domain walls, we provide an analytic formula that expresses the so-called "nonadiabatic" (or fieldlike) torque in terms of these length scales. However, this nonadiabatic torque is no longer a simple material parameter but depends on the actual spin texture: in thin (<10 nm) domain walls, we observe very significant deviations from the adiabatic limit.
Seemann, Klaus; Garcia-Sanchez, Felipe; Kakay, Attila; Schneider, Claus; Freimuth, Frank; Mokrousov, Yuriy; Bluegel, Stefan; Hertel, Riccardo
2012-02-01
We analyze the origin of the electrical resistance arising in domain walls of perpendicularly magnetized materials by considering a superposition of anisotropic magnetoresistance and the resistance implied by the magnetization chirality. The domain wall profiles of L10-FePd and L10-FePt are determined by micromagnetic simulations based on which we perform first principles calculations to quantify electron transport through the core and closure region of the walls. The wall resistance, being twice as high in L10-FePd than in L10-FePt, is found to be clearly dominated in both cases by a high gradient of magnetization rotation, and not by the spin-orbit interaction driven anisotropic magnetoresistance effect. Concerning the anomalous Hall effect on the other hand, we show that difference in spin-orbit interaction strength of Pt and Pd atoms leads to a pronounced cross-over from an extrinsic side jump mechanism in L10-FePd to an intrinsic Berry-phase anomalous Hall effect in L10-FePt.
Current-induced domain wall motion in nanoscale ferromagnetic elements
Energy Technology Data Exchange (ETDEWEB)
Malinowski, G [Laboratoire de Physique des Solides, CNRS, Universite Paris-sud 11, 91405 Orsay Cedex (France); Boulle, O [SPINTEC, CEA/CNRS/UJF/GINP, INAC, 38054 Grenoble Cedex 9 (France); Klaeui, M, E-mail: Klaeui@uni-mainz.de [SwissFEL, Paul Scherrer Institut, 5232 Villigen PSI (Switzerland); Laboratory of Nanomagnetism and Spin Dynamics, Ecole Polytechnique Federale de Lausanne (EPFL), 1015 Lausanne (Switzerland)
2011-09-28
We review the details of domain wall (DW) propagation due to spin-polarized currents that could potentially be used in magnetic data storage devices based on domains and DWs. We discuss briefly the basics of the underlying spin torque effect and show how the two torques arising from the interaction between the spin-polarized charge carriers and the magnetization lead to complex dynamics of a spin texture such as a DW. By direct imaging we show how confined DWs in nanowires can be displaced using currents in in-plane soft-magnetic materials, and that when using short pulses, fast velocities can be attained. For high-anisotropy out-of-plane magnetized wires with narrow DWs we present approaches to deducing the torque terms and show that in these materials potentially more efficient domain wall motion could be achieved.
Performance of synthetic antiferromagnetic racetrack memory: domain wall versus skyrmion
Tomasello, R.; Puliafito, V.; Martinez, E.; Manchon, A.; Ricci, M.; Carpentieri, M.; Finocchio, G.
2017-08-01
A storage scheme based on racetrack memory, where the information can be coded in a domain or a skyrmion, seems to be an alternative to conventional hard disk drive for high density storage. Here, we perform a full micromagnetic study of the performance of synthetic antiferromagnetic (SAF) racetrack memory in terms of velocity and sensitivity to defects by using experimental parameters. We find that, to stabilize a SAF skyrmion, the Dzyaloshinskii-Moriya interaction in the top and the bottom ferromagnet should have an opposite sign. The velocity of SAF skyrmions and SAF Néel domain walls are of the same order and can reach values larger than 1200 m s-1 if a spin-orbit torque from the spin-Hall effect with opposite sign is applied to both ferromagnets. The presence of disordered anisotropy in the form of randomly distributed grains introduces a threshold current for both SAF skyrmions and SAF domain walls motions.
Performance of synthetic antiferromagnetic racetrack memory: domain wall versus skyrmion
Tomasello, R
2017-06-20
A storage scheme based on racetrack memory, where the information can be coded in a domain or a skyrmion, seems to be an alternative to conventional hard disk drive for high density storage. Here, we perform a full micromagnetic study of the performance of synthetic antiferromagnetic (SAF) racetrack memory in terms of velocity and sensitivity to defects by using experimental parameters. We find that, to stabilize a SAF skyrmion, the Dzyaloshinskii–Moriya interaction in the top and the bottom ferromagnet should have an opposite sign. The velocity of SAF skyrmions and SAF Néel domain walls are of the same order and can reach values larger than 1200 m s−1 if a spin–orbit torque from the spin-Hall effect with opposite sign is applied to both ferromagnets. The presence of disordered anisotropy in the form of randomly distributed grains introduces a threshold current for both SAF skyrmions and SAF domain walls motions.
Non-volatile polarization switch of magnetic domain wall velocity
Energy Technology Data Exchange (ETDEWEB)
Huang, Z.; Stolichnov, I.; Setter, N. [Ceramics Laboratory, EPFL-Swiss Federal Institute of Technology, Lausanne 1015 (Switzerland); Bernand-Mantel, A.; Schott, Marine; Pizzini, S.; Ranno, L. [University of Grenoble Alpes, Institut Néel, F-38042 Grenoble (France); CNRS, Institut Néel, F-38042 Grenoble (France); Auffret, S.; Gaudin, G. [SPINTEC, UMR-8191, CEA/CNRS/UJF/GINP, INAC, F-38054 Grenoble (France)
2015-12-21
Controlled propagation speed of individual magnetic domains in metal channels at the room temperature is obtained via the non-volatile field effect associated with the switchable polarization of P(VDF-TrFE) (polyvinylidene fluoride-trifluoroethylene) ferroelectric polymer. Polarization domains directly written using conducting atomic force microscope probe locally accelerate/decelerate the magnetic domains in the 0.6 nm thick Co film. The change of the magnetic domain wall velocity is consistent with the magnetic anisotropy energy modulation through the polarization upward/downward orientation. Excellent retention is observed. The demonstrated local non-destructive and reversible change of magnetic properties via rewritable patterning of ferroelectric domains could be attractive for exploring the ultimate limit of miniaturization in devices based on ferromagnetic/ferroelectric bilayers.
Rashba Torque Driven Domain Wall Motion in Magnetic Helices.
Pylypovskyi, Oleksandr V; Sheka, Denis D; Kravchuk, Volodymyr P; Yershov, Kostiantyn V; Makarov, Denys; Gaididei, Yuri
2016-01-01
Manipulation of the domain wall propagation in magnetic wires is a key practical task for a number of devices including racetrack memory and magnetic logic. Recently, curvilinear effects emerged as an efficient mean to impact substantially the statics and dynamics of magnetic textures. Here, we demonstrate that the curvilinear form of the exchange interaction of a magnetic helix results in an effective anisotropy term and Dzyaloshinskii-Moriya interaction with a complete set of Lifshitz invariants for a one-dimensional system. In contrast to their planar counterparts, the geometrically induced modifications of the static magnetic texture of the domain walls in magnetic helices offer unconventional means to control the wall dynamics relying on spin-orbit Rashba torque. The chiral symmetry breaking due to the Dzyaloshinskii-Moriya interaction leads to the opposite directions of the domain wall motion in left- or right-handed helices. Furthermore, for the magnetic helices, the emergent effective anisotropy term and Dzyaloshinskii-Moriya interaction can be attributed to the clear geometrical parameters like curvature and torsion offering intuitive understanding of the complex curvilinear effects in magnetism.
Domain Walls in Supersymmetric Yang-Mills Theories
Kaplunovsky, V S; Yankielowicz, Shimon; Kaplunovsky, Vadim S.; Sonnenschein, Jacob; Yankielowicz, Shimon
1999-01-01
We study BPS saturated domain walls in the supersymmetric SU(2) gauge theory. For a theory with a very light adjoint scalar (mass <~ Lambda/400) we use the perturbed N=2 Seiberg-Witten theory to calculate the actual field configuration of the domain wall. The wall has a sandwich-like five-layer structure of three distinct phases -- electric confinement, Coulomb and oblique confinement -- separated by two separate transition regions. For larger scalar masses, the three-phase structure disappears and the Seiberg-Witten theory becomes inadequate because of two major problems: First, the higher-derivative interactions between the light fields become relevant and second, both the magnetic monopole condensate and the dyon condensate show up in the same region of space, a phenomenon indescribable in terms of a local field theory. Nevertheless, we argue that the BPS saturated domain wall continues to exist in this regime and give a qualitative description of the scalar and gaugino condensates. Finally, we discuss ...
Hall effect in charged conducting ferroelectric domain walls.
Campbell, M P; McConville, J P V; McQuaid, R G P; Prabhakaran, D; Kumar, A; Gregg, J M
2016-12-12
Enhanced conductivity at specific domain walls in ferroelectrics is now an established phenomenon. Surprisingly, however, little is known about the most fundamental aspects of conduction. Carrier types, densities and mobilities have not been determined and transport mechanisms are still a matter of guesswork. Here we demonstrate that intermittent-contact atomic force microscopy (AFM) can detect the Hall effect in conducting domain walls. Studying YbMnO3 single crystals, we have confirmed that p-type conduction occurs in tail-to-tail charged domain walls. By calibration of the AFM signal, an upper estimate of ∼1 × 10(16) cm(-3) is calculated for the mobile carrier density in the wall, around four orders of magnitude below that required for complete screening of the polar discontinuity. A carrier mobility of∼50 cm(2)V(-1)s(-1) is calculated, about an order of magnitude below equivalent carrier mobilities in p-type silicon, but sufficiently high to preclude carrier-lattice coupling associated with small polarons.
Hall effect in charged conducting ferroelectric domain walls
Campbell, M. P.; McConville, J. P. V.; McQuaid, R. G. P.; Prabhakaran, D.; Kumar, A.; Gregg, J. M.
2016-12-01
Enhanced conductivity at specific domain walls in ferroelectrics is now an established phenomenon. Surprisingly, however, little is known about the most fundamental aspects of conduction. Carrier types, densities and mobilities have not been determined and transport mechanisms are still a matter of guesswork. Here we demonstrate that intermittent-contact atomic force microscopy (AFM) can detect the Hall effect in conducting domain walls. Studying YbMnO3 single crystals, we have confirmed that p-type conduction occurs in tail-to-tail charged domain walls. By calibration of the AFM signal, an upper estimate of ~1 × 1016 cm-3 is calculated for the mobile carrier density in the wall, around four orders of magnitude below that required for complete screening of the polar discontinuity. A carrier mobility of~50 cm2V-1s-1 is calculated, about an order of magnitude below equivalent carrier mobilities in p-type silicon, but sufficiently high to preclude carrier-lattice coupling associated with small polarons.
Energy Technology Data Exchange (ETDEWEB)
Whyte, J. R.; McQuaid, R. G. P.; Einsle, J. F.; Gregg, J. M., E-mail: m.gregg@qub.ac.uk [Centre for Nanostructured Media (CNM), School of Maths and Physics, Queen' s University Belfast, University Road, Belfast BT7 1NN (United Kingdom); Ashcroft, C. M. [Centre for Nanostructured Media (CNM), School of Maths and Physics, Queen' s University Belfast, University Road, Belfast BT7 1NN (United Kingdom); Department of Physics, Cavendish Laboratory, J. J. Thomson Avenue, Cambridge CB3 0HE (United Kingdom); Canalias, C. [Department of Applied Physics, Royal Institute of Technology, Roslagstullsbacken 21, 10691 Stockholm (Sweden); Gruverman, A. [Department of Physics and Astronomy, University of Nebraska Lincoln, Nebraska 68588–0299 (United States)
2014-08-14
Simple meso-scale capacitor structures have been made by incorporating thin (∼300 nm) single crystal lamellae of KTiOPO{sub 4} (KTP) between two coplanar Pt electrodes. The influence that either patterned protrusions in the electrodes or focused ion beam milled holes in the KTP have on the nucleation of reverse domains during switching was mapped using piezoresponse force microscopy imaging. The objective was to assess whether or not variations in the magnitude of field enhancement at localised “hot-spots,” caused by such patterning, could be used to both control the exact locations and bias voltages at which nucleation events occurred. It was found that both the patterning of electrodes and the milling of various hole geometries into the KTP could allow controlled sequential injection of domain wall pairs at different bias voltages; this capability could have implications for the design and operation of domain wall electronic devices, such as memristors, in the future.
Domain Walls: Momentum Conservation in Absence of Asymptotic States
Gal'tsov, D V; Spirin, P
2016-01-01
Gravitational potentials of the domain walls in the linearized gravity are growing with distance, so the particle scattering by the wall can not be described in terms of free asymptotic states. In the non-relativistic case this problem is solved using the concept of the potential energy. We show that in the relativistic case one is able to introduce gravitationally dressed momenta the sum of which is conserved up to the momentum flux through the lateral surface of the world tube describing losses due to excitation of the branon waves.
Characterization of magnetic domain walls using electron magnetic chiral dichroism
Directory of Open Access Journals (Sweden)
Ren Chao Che, Chong Yun Liang, Xiang He, Hai Hua Liu and Xiao Feng Duan
2011-01-01
Full Text Available Domain walls and spin states of permalloy were investigated by electron magnetic chiral dichroism (EMCD technique in Lorentz imaging mode using a JEM-2100F transmission electron microscope. EMCD signals from both Fe and Ni L3,2 edges were detected from the Bloch lines but not from the adjacent main wall. The magnetic polarity orientation of the circular Bloch line is opposite to that of the cross Bloch line. The orientations of Fe and Ni spins are parallel rather than antiparallel, both at the cross Bloch line and circular Bloch line.
Domain wall motion by the magnonic spin Seebeck effect.
Hinzke, D; Nowak, U
2011-07-08
The recently discovered spin Seebeck effect refers to a spin current induced by a temperature gradient in a ferromagnetic material. It combines spin degrees of freedom with caloric properties, opening the door for the invention of new, spin caloritronic devices. Using spin model simulations as well as an innovative, multiscale micromagnetic framework we show that magnonic spin currents caused by temperature gradients lead to spin transfer torque effects, which can drag a domain wall in a ferromagnetic nanostructure towards the hotter part of the wire. This effect opens new perspectives for the control and manipulation of domain structures.
Domain-wall spin dynamics in kagome antiferromagnets.
Lhotel, E; Simonet, V; Ortloff, J; Canals, B; Paulsen, C; Suard, E; Hansen, T; Price, D J; Wood, P T; Powell, A K; Ballou, R
2011-12-16
We report magnetization and neutron scattering measurements down to 60 mK on a new family of Fe based kagome antiferromagnets, in which a strong local spin anisotropy combined with a low exchange path network connectivity lead to domain walls intersecting the kagome planes through strings of free spins. These produce unfamiliar slow spin dynamics in the ordered phase, evolving from exchange-released spin flips towards a cooperative behavior on decreasing the temperature, probably due to the onset of long-range dipolar interaction. A domain structure of independent magnetic grains is obtained that could be generic to other frustrated magnets.
Exact BPS domain walls at finite gauge coupling
Blaschke, Filip
2016-01-01
Bogomol'nyi-Prasad-Sommerfield solitons in models with spontaneously broken gauge symmetry have been intensively studied at infinite gauge coupling limit, where the governing equation -- so-called master equation -- is exactly solvable. Except of handful of special solutions, the standing impression is that analytic results at finite coupling are generally unavailable. The aim of this paper is to demonstrate, using domain walls in Abelian-Higgs models as a simplest example, that exact solitons at finite gauge coupling can be readily obtained, if the number of Higgs fields ($N_F$) is large enough. In particular, we present a family of exact solutions, describing $N$ domain walls at arbitrary positions in models with at least $N_F \\geq 2N+1$. We have also found that adding together any pair of solution can produce a new exact solution, if the combined tension is below certain limit.
Magnetic domain walls of relic neutrinos as Dark Energy
Yajnik, U A
2006-01-01
The observed Dark Energy component of the cosmic energy density is well fitted by domain wall matter which scales as $S(t)^{-1}$ where $S$ is the Friedmann-Robertson-Walker (FRW) scale factor. We show that relic neutrinos of the Big Bang can enter a ferromagnetic state governed by Stoner theory provided they are a degenerate gas and possess a magnetic moment. The domain walls of this ferromagnetism behave as Dark Energy. The degeneracy requirement accords with Big Bang nucleosynthesis expectations of large chemical potentials for neutrinos and provides an estimate for the same. At least one of the the mass eigenstate neutrinos would have to possess a magnetic moment greater than $10^{-9}$ Bohr magneton. Any other relic contributing to Hot Dark Matter could also provide an interesting candidate.
2003-01-01
Universidad Aut6noma de Madrid, 28049, Madrid, Spain (2) CMIT, University of Alabama, Tuscaloosa, USA (3) Instituto de Ciencia de Materiales Madrid...research was supported in parts by Spanish MCyT under project BFM2000-0016 and by Comunidad de Madrid (07N/0049/2001), 87 References [1] L.Berger, J
Analysis of ultra-narrow ferromagnetic domain walls
Energy Technology Data Exchange (ETDEWEB)
Jenkins, Catherine; Paul, David
2012-01-10
New materials with high magnetic anisotropy will have domains separated by ultra-narrow ferromagnetic walls with widths on the order of a few unit cells, approaching the limit where the elastic continuum approximation often used in micromagnetic simulations is accurate. The limits of this approximation are explored, and the static and dynamic interactions with intrinsic crystalline defects and external driving elds are modeled. The results developed here will be important when considering the stability of ultra-high-density storage media.
Critical domain-wall dynamics of model B.
Dong, R H; Zheng, B; Zhou, N J
2009-05-01
With Monte Carlo methods, we simulate the critical domain-wall dynamics of model B, taking the two-dimensional Ising model as an example. In the macroscopic short-time regime, a dynamic scaling form is revealed. Due to the existence of the quasirandom walkers, the magnetization shows intrinsic dependence on the lattice size L . An exponent which governs the L dependence of the magnetization is measured to be sigma=0.243(8) .
Experimental Study on Current-Driven Domain Wall Motion
Ono, T.; Yamaguchi, A.; Tanigawa, H.; Yano, K.; Kasai, S.
2006-06-01
Current-driven domain wall (DW) motion for a well-defined single DW in a micro-fabricated magnetic wire with submicron width was investigated by real-space observation with magnetic force microscopy. Magnetic force microscopy visualizes that a single DW introduced in a wire is displaced back and forth by positive and negative pulsed-current, respectively. Effect of the Joule heating, reduction of the threshold current density by shape control, and magnetic ratchet effect are also presented.
Quark Number Susceptibilities with Domain-Wall Fermions
Hegde, Prasad; Schmidt, Christian
2008-01-01
We present results from calculations of different quark number and hadronic susceptibilities on 2+1-flavor dynamical domain wall ensembles. We find that the iso-spin and electric charge susceptibilities are especially well suited to determine the transition temperature, as these quantities show only small statistical errors. Moreover, the transition values of the coupling obtained from iso-spin and electrical charge susceptibilities are in good agreement with the one obtained from the chiral condensate.
Factorized domain wall partition functions in trigonometric vertex models
Foda, O; Zuparic, M
2007-01-01
We obtain factorized domain wall partition functions for two sets of trigonometric vertex models: 1. The N-state Deguchi-Akutsu models, for N = {2, 3, 4} (and conjecture the result for all N >= 5), and 2. The sl(r+1|s+1) Perk-Schultz models, for {r, s = \\N}, where (given the symmetries of these models) the result is independent of {r, s}.
Dynamics of Biased Domain Walls and the Devaluation Mechanism
Pina-Avelino, P; Sousa, L
2008-01-01
We study the evolution of biased domain walls in the early universe. We explicitly discuss the roles played by the surface tension and volume pressure in the evolution of the walls, and quantify their effects by looking at the collapse of spherical wall solutions. We then apply our results to a particular mechanism, known as the devaluation scenario, in which the dynamics of biased domain walls was suggested as a possible solution to the cosmological constant problem. Our results indicate that devaluation will in general lead to values of the cosmological constant that differ by several orders of magnitude from the observationally inferred value, $\\rho^{1/4}_{vac}\\sim10^{-3} \\rm eV$. We also argue that the reasons behind this are not specific to a particular realization, and are expected to persist in any scenario of this kind, except if a low energy cut-off on the spectra of vacuum energy densities, of the order of the critical density at the present time, is postulated. This implies that any such scenario w...
Dynamics of biased domain walls and the devaluation mechanism
Avelino, P. P.; Martins, C. J. A. P.; Sousa, L.
2008-08-01
We study the evolution of biased domain walls in the early universe. We explicitly discuss the roles played by the surface tension and volume pressure in the evolution of the walls, and quantify their effects by looking at the collapse of spherical wall solutions. We then apply our results to a particular mechanism, known as the devaluation scenario, in which the dynamics of biased domain walls was suggested as a possible solution to the cosmological constant problem. Our results indicate that devaluation will, in general, lead to values of the cosmological constant that differ by several orders of magnitude from the observationally inferred value, ρvac1/4˜10-3eV. We also argue that the reasons behind this are not specific to a particular realization, and are expected to persist in any scenario of this kind, except if a low-energy cutoff on the spectra of vacuum energy densities, of the order of the critical density at the present time, is postulated. This implies that any such scenario will require a fine-tuning similar to the usual one.
The M\\"obius Domain Wall Fermion Algorithm
Brower, Richard C; Orginos, Kostas
2012-01-01
We present a review of the properties of generalized domain wall Fermions, based on a (real) M\\"obius transformation on the Wilson overlap kernel, discussing their algorithmic efficiency, the degree of explicit chiral violations measured by the residual mass ($m_{res}$) and the Ward-Takahashi identities. The M\\"obius class interpolates between Shamir's domain wall operator and Bori\\c{c}i's domain wall implementation of Neuberger's overlap operator without increasing the number of Dirac applications per conjugate gradient iteration. A new scaling parameter ($\\alpha$) reduces chiral violations at finite fifth dimension ($L_s$) but yields exactly the same overlap action in the limit $L_s \\rightarrow \\infty$. Through the use of 4d Red/Black preconditioning and optimal tuning for the scaling $\\alpha(L_s)$, we show that chiral symmetry violations are typically reduced by an order of magnitude at fixed $L_s$. At large $L_s$ we argue that the observed scaling for $m_{res} = O(1/L_s)$ for Shamir is replaced by $m_{res...
Institute of Scientific and Technical Information of China (English)
WEN Qi-Ye; ZHANG Huai-Wu; JIANG Xiang-Dong; SHI Yu; TANG Xiao-Li; ZHANG Wan-Li
2004-01-01
@@ We propose a pseudo-spin-valve (PSV) trilayer using amorphous CoNbZr alloy for soft magnetic layers. The giant magnetoresistance (GMR), domain structures and their variation upon thermal annealing are investigated. The GMR effect is not only stable up to 300℃ but also enhanced due to the improvement of the interfaces between Cu and magnetic layers. With high annealing temperature, the magnetoresistance (MR) ratio decreases rapidly as a result of serious layer interdiffusion. Dense stripe domains, which disappear after annealing at 300℃ for 1 h, are observed in the sandwiched films. It is found that after patterning to elliptic stripe with aspect ratio of 6:1, the trilayers have a single domain and their MR ratio increases. The dynamic MR behaviour under an ac magnetic field indicates that the patterned stripes have good linear MR responses. Therefore, it is believed that the CoNbZr/Cu/Co PSV trilayers have strong potentials for spin-electronic devices including magnetic random access memory.
Coupled Néel domain wall motion in sandwiched perpendicular magnetic anisotropy nanowires
Purnama, I.; Kerk, I. S.; Lim, G J; Lew, W. S.
2015-01-01
The operating performance of a domain wall-based magnetic device relies on the controlled motion of the domain walls within the ferromagnetic nanowires. Here, we report on the dynamics of coupled Néel domain wall in perpendicular magnetic anisotropy (PMA) nanowires via micromagnetic simulations. The coupled Néel domain wall is obtained in a sandwich structure, where two PMA nanowires that are separated by an insulating layer are stacked vertically. Under the application of high current densit...
Energy Technology Data Exchange (ETDEWEB)
Zhmetko, D.N., E-mail: sergey.zhmetko@gmail.com [Department of Physics, Zaporizhzhya National University, 66 Zhukovsky Street, 69063 Zaporizhzhya (Ukraine); Zhmetko, S.D. [Department of Physics, Zaporizhzhya National University, 66 Zhukovsky Street, 69063 Zaporizhzhya (Ukraine); Troschenkov, Y.N. [Institute for Magnetism, 36-b Vernadsky Boulevard, 03142 Kyiv (Ukraine); Matsura, A.V. [Department of Physics, Zaporizhzhya National University, 66 Zhukovsky Street, 69063 Zaporizhzhya (Ukraine)
2013-08-15
The frequency dependence of asymmetry of the domain walls velocity relative to the middle plane of amorphous ribbon is investigated. An additional pressure of the same direction acting on each domain wall caused by dependence of eddy current damping on the coordinate of the domain wall is revealed. The microscopic mechanisms of this additional pressure are considered. - Highlights: ► Additional pressure on the domain wall, caused by inhomogeneity of its damping. ► Asymmetry of the coordinate of the nucleation of domain walls and their damping. ► Connection between the components of additional pressure and its direction. ► Interaction of domain walls with the surface defects of the amorphous ribbon.
Controlled motion of domain walls in submicron amorphous wires
Directory of Open Access Journals (Sweden)
Mihai Ţibu
2016-05-01
Full Text Available Results on the control of the domain wall displacement in cylindrical Fe77.5Si7.5B15 amorphous glass-coated submicron wires prepared by rapid quenching from the melt are reported. The control methods have relied on conical notches with various depths, up to a few tens of nm, made in the glass coating and in the metallic nucleus using a focused ion beam (FIB system, and on the use of small nucleation coils at one of the sample ends in order to apply magnetic field pulses aimed to enhance the nucleation of reverse domains. The notch-based method is used for the first time in the case of cylindrical ultrathin wires. The results show that the most efficient technique of controlling the domain wall motion in this type of samples is the simultaneous use of notches and nucleation coils. Their effect depends on wire diameter, notch depth, its position on the wire length, and characteristics of the applied pulse.
Cosmic bubble and domain wall instabilities II: Fracturing of Colliding Walls
Braden, Jonathan; Mersini-Houghton, Laura
2015-01-01
We study collisions between nearly planar domain walls including the effects of small initial nonplanar fluctuations. These perturbations represent the small fluctuations that must exist in a quantum treatment of the problem. In a previous paper, we demonstrated that at the linear level a subset of these fluctuations experience parametric amplification as a result of their coupling to the planar symmetric background. Here we study the full three-dimensional nonlinear dynamics using lattice simulations, including both the early time regime when the fluctuations are well described by linear perturbation theory as well as the subsequent stage of fully nonlinear evolution. We find that the nonplanar fluctuations have a dramatic effect on the overall evolution of the system. Specifically, once these fluctuations begin to interact nonlinearly the split into a planar symmetric part of the field and the nonplanar fluctuations loses its utility. At this point the colliding domain walls dissolve, with the endpoint of t...
Higher dimensional curved domain walls on Kähler surfaces
Akbar, Fiki T.; Gunara, Bobby E.; Radjabaycolle, Flinn C.; Wijaya, Rio N.
2017-03-01
In this paper we study some aspects of curved BPS-like domain walls in higher dimensional gravity theory coupled to scalars where the scalars span a complex Kähler surface with scalar potential turned on. Assuming that a fake superpotential has a special form which depends on Kähler potential and a holomorphic function, we prove that BPS-like equations have a local unique solution. Then, we analyze the vacuum structure of the theory including their stability using dynamical system and their existence in ultraviolet-infrared regions using renormalization group flow.
On the trigonometric Felderhof model with domain wall boundary conditions
Caradoc, A; Wheeler, M; Zuparic, M; 10.1088/1742-5468/2007/03/P03010
2008-01-01
We consider the trigonometric Felderhof model, of free fermions in an external field, on a finite lattice with domain wall boundary conditions. The vertex weights are functions of rapidities and external fields. We obtain a determinant expression for the partition function in the special case where the dependence on the rapidities is eliminated, but for general external field variables. This determinant can be evaluated in product form. In the homogeneous limit, it is proportional to a 2-Toda tau function. Next, we use the algebraic Bethe ansatz factorized basis to obtain a product expression for the partition function in the general case with dependence on all variables.
Higher dimensional curved domain walls on Kähler surfaces
Energy Technology Data Exchange (ETDEWEB)
Akbar, Fiki T., E-mail: ftakbar@fi.itb.ac.id [Theoretical Physics Laboratory, Theoretical High Energy Physics and Instrumentation Research Group, Faculty of Mathematics and Natural Sciences, Institut Teknologi Bandung, Jl. Ganesha no. 10 Bandung, 40132 (Indonesia); Gunara, Bobby E., E-mail: bobby@fi.itb.ac.id [Theoretical Physics Laboratory, Theoretical High Energy Physics and Instrumentation Research Group, Faculty of Mathematics and Natural Sciences, Institut Teknologi Bandung, Jl. Ganesha no. 10 Bandung, 40132 (Indonesia); Radjabaycolle, Flinn C. [Theoretical Physics Laboratory, Theoretical High Energy Physics and Instrumentation Research Group, Faculty of Mathematics and Natural Sciences, Institut Teknologi Bandung, Jl. Ganesha no. 10 Bandung, 40132 (Indonesia); Departement of Physics, Faculty of Mathematics and Natural Sciences, Cendrawasih University, Jl. Kampwolker Kampus Uncen Baru Waena-Jayapura 99351 (Indonesia); Wijaya, Rio N. [Theoretical Physics Laboratory, Theoretical High Energy Physics and Instrumentation Research Group, Faculty of Mathematics and Natural Sciences, Institut Teknologi Bandung, Jl. Ganesha no. 10 Bandung, 40132 (Indonesia)
2017-03-15
In this paper we study some aspects of curved BPS-like domain walls in higher dimensional gravity theory coupled to scalars where the scalars span a complex Kähler surface with scalar potential turned on. Assuming that a fake superpotential has a special form which depends on Kähler potential and a holomorphic function, we prove that BPS-like equations have a local unique solution. Then, we analyze the vacuum structure of the theory including their stability using dynamical system and their existence in ultraviolet-infrared regions using renormalization group flow.
Dielectric relaxation and charged domain walls in (K,Na)NbO3-based ferroelectric ceramics
Esin, A. A.; Alikin, D. O.; Turygin, A. P.; Abramov, A. S.; Hreščak, J.; Walker, J.; Rojac, T.; Bencan, A.; Malic, B.; Kholkin, A. L.; Shur, V. Ya.
2017-02-01
The influence of domain walls on the macroscopic properties of ferroelectric materials is a well known phenomenon. Commonly, such "extrinsic" contributions to dielectric permittivity are discussed in terms of domain wall displacements under external electric field. In this work, we report on a possible contribution of charged domain walls to low frequency (10-106 Hz) dielectric permittivity in K1-xNaxNbO3 ferroelectric ceramics. It is shown that the effective dielectric response increases with increasing domain wall density. The effect has been attributed to the Maxwell-Wagner-Sillars relaxation. The obtained results may open up possibilities for domain wall engineering in various ferroelectric materials.
Halstead, Evan
2011-01-01
We investigate the time evolution of the temperature and entropy of a gravitationally collapsing de Sitter Schwarzschild domain wall as seen by an asymptotic observer. Recent work has completed this analysis for Schwarzschild and 3+1 BTZ domain walls. There were some striking qualitative differences between the two. Specifically, the BTZ domain wall exhibited a decrease in entropy over time. However, it contained both a cosmological constant and a different topology from the Schwarzschild domain wall, and we wish to isolate which of these is responsible for the qualitative differences. Hence, we will study the de Sitter Schwarzschild domain wall, as it has identical topology to the Schwarzschild domain wall yet also contains a cosmological constant. We utilize a wavefunctional approach where we couple a scalar field to the background of the collapsing domain wall and determine the spectrum of the radiation as a function of time. The fact that the distribution is thermal allows for the determination of the tem...
Magnetic domain wall induced ferroelectricity in double perovskites
Energy Technology Data Exchange (ETDEWEB)
Zhou, Hai Yang; Zhao, Hong Jian, E-mail: dielectric-hjzhao@126.com, E-mail: xmchen59@zju.edu.cn; Chen, Xiang Ming, E-mail: dielectric-hjzhao@126.com, E-mail: xmchen59@zju.edu.cn [Laboratory of Dielectric Materials, Department of Materials Science and Engineering, Zhejiang University, 38 Zheda Road, Hangzhou 310027 (China); Zhang, Wen Qing [Department of Physics, Shanghai University, 99 Shangda Road, Shanghai 200444 (China)
2015-04-13
Recently, a magnetically induced ferroelectricity occurring at magnetic domain wall of double perovskite Lu{sub 2}CoMnO{sub 6} has been reported experimentally. However, there exists a conflict whether the electric polarization is along b or c direction. Here, by first-principles calculations, we show that the magnetic domain wall (with ↑↑↓↓ spin configuration) can lead to the ferroelectric displacements of R{sup 3+}, Ni{sup 2+}, Mn{sup 4+}, and O{sup 2−} ions in double perovskites R{sub 2}NiMnO{sub 6} (R = rare earth ion) via exchange striction. The resulted electric polarization is along b direction with the P2{sub 1} symmetry. We further reveal the origin of the ferroelectric displacements as that: (1) on a structural point of view, such displacements make the two out-of-plane Ni-O-Mn bond angles as well as Ni-Mn distance unequal, and (2) on an energy point of view, such displacements weaken the out-of-plane Ni-Mn super-exchange interaction obviously. Finally, our calculations show that such a kind of ferroelectric order is general in ferromagnetic double perovskites.
Chiral damping in magnetic domain-walls (Conference Presentation)
Jue, Emilie; Safeer, C. K.; Drouard, Marc; Lopez, Alexandre; Balint, Paul; Buda-Prejbeanu, Liliana; Boulle, Olivier; Auffret, Stéphane; Schuhl, Alain; Manchon, Aurélien; Miron, Ioan Mihai; Gaudin, Gilles
2016-10-01
The Dzyaloshinskii-Moriya interaction is responsible for chiral magnetic textures (skyrmions, spin spiral structures, …) in systems with structural inversion asymmetry and high spin-orbit coupling. It has been shown that the domain wall (DW) dynamics in such materials can be explained by chiral DWs with (partly or fully) Néel structure, whose stability derives from an interfacial DMI [1]. In this work, we show that DMI is not the only effect inducing chiral dynamics and demonstrate the existence of a chiral damping [2]. This result is supported by the study of the asymmetry induced by an in-plane magnetic field on field induced domain wall motion in perpendicularly magnetized asymmetric Pt/Co/Pt trilayers. Whereas the asymmetry of the DW motion is consistent with the spatial symmetries expected with the DMI, we show that this asymmetry cannot be attributed to an effective field but originates from a purely dissipative mechanism. The observation of chiral damping, not only enriches the spectrum of physical phenomena engendered by the SIA, but since it can coexist with DMI it is essential for conceiving DW and skyrmion devices. [1] A. Thiaville, et al., EPL 100, 57002 (2012) [2] E. Jué, et al., Nat. Mater., in press (doi: 10.1038/nmat4518)
Energy-momentum balance in particle - domain wall perforating collision
Gal'tsov, D V; Spiirin, P A
2014-01-01
We investigate the energy-momentum balance in the perforating collision of a point particle with an infinitely thin planar domain wall within the linearized gravity in arbitrary dimensions. Since the metric of the wall increases with distance, the wall and the particle are never free, and their energy-momentum balance involves not only the instantaneous kinetic momenta, but also the non-local contribution of gravitational stresses. However, careful analysis shows that the stresses can be unambiguously divided between the colliding objects leading to definition of the gravitationally dressed momenta. These take into account for gravity in the same way as the potential energy does in the non-relativistic theory, but our treatment is fully relativistic. Another unusual feature of our problem is the non-vanishing flux of the total energy-momentum tensor through the lateral surface of the world tube. In this case the zero divergence of the energy-momentum tensor does not imply conservation of the total momentum de...
Soliton-dependent plasmon reflection at bilayer graphene domain walls.
Jiang, Lili; Shi, Zhiwen; Zeng, Bo; Wang, Sheng; Kang, Ji-Hun; Joshi, Trinity; Jin, Chenhao; Ju, Long; Kim, Jonghwan; Lyu, Tairu; Shen, Yuen-Ron; Crommie, Michael; Gao, Hong-Jun; Wang, Feng
2016-08-01
Layer-stacking domain walls in bilayer graphene are emerging as a fascinating one-dimensional system that features stacking solitons structurally and quantum valley Hall boundary states electronically. The interactions between electrons in the 2D graphene domains and the one-dimensional domain-wall solitons can lead to further new quantum phenomena. Domain-wall solitons of varied local structures exist along different crystallographic orientations, which can exhibit distinct electrical, mechanical and optical properties. Here we report soliton-dependent 2D graphene plasmon reflection at different 1D domain-wall solitons in bilayer graphene using near-field infrared nanoscopy. We observe various domain-wall structures in mechanically exfoliated graphene bilayers, including network-forming triangular lattices, individual straight or bent lines, and even closed circles. The near-field infrared contrast of domain-wall solitons arises from plasmon reflection at domain walls, and exhibits markedly different behaviours at the tensile- and shear-type domain-wall solitons. In addition, the plasmon reflection at domain walls exhibits a peculiar dependence on electrostatic gating. Our study demonstrates the unusual and tunable coupling between 2D graphene plasmons and domain-wall solitons.
Chen, Hong-Bo; Li, You-Quan
2016-07-01
We theoretically study the dynamics of a magnetic domain wall controlled by an electric field in the presence of the spin flexoelectric interaction. We reveal that this interaction generates an effective spin torque and results in significant changes in the current-driven domain wall motion. In particular, the electric field can stabilize the domain wall motion, leading to strong suppression of the current-induced Walker breakdown and thus allowing a higher maximum wall velocity. We can furthermore use this electric-field control to efficiently switch the chirality of a moving domain wall in the steady regime.
Efficient stopping of current-driven domain wall using a local Rashba field
Tatara, Gen; Saarikoski, Henri; Mitsumata, Chiharu
2016-10-01
We show theoretically that a locally embedded Rashba interaction acts as a strong pinning center for current-driven domain walls and demonstrate efficient capturing and depinning of the wall using a weak Rashba interaction of the order of 0.01 eV Å. Our discovery is expected to be useful for highly reliable control of domain walls in racetrack memories.
Gravitational ﬁeld of spherical domain wall in higher dimension
Indian Academy of Sciences (India)
Farook Rahaman; Mehedi Kalam
2002-01-01
An exact solution of Einstein’s equations is found describing the gravitational ﬁeld of a spherical domain wall with nonvanishing stress component in the direction perpendicular to the plane of the wall. Also we have studied the motion of test particle around the domain wall.
Altering critical depinning current via domain wall pile-up in magnetic nanowires
Energy Technology Data Exchange (ETDEWEB)
Geng, Liwei D.; Jin, Yongmei M., E-mail: ymjin@mtu.edu
2015-11-01
An important role of domain wall pile-up in current-driven domain wall depinning in magnetic nanowires is revealed using micromagnetic simulations. It is found that the critical current for domain wall depinning can be substantially reduced and conveniently tuned by controlling domain wall number in the pile-up at pinning site, in analogy to dislocation pile-up responsible for Hall–Petch effect in mechanical strength. Domain wall pinning and depinning at an s-shape bend is considered, and the effects of curvature and current crowding in magnetic circuit on domain wall behaviors are discussed. - Highlights: • Advance fundamental knowledge of current-driven domain wall phenomena. • Provide a novel approach to drastically reduce the critical depinning current. • Solve an outstanding problem of effective control of domain wall pinning/depinning. • Report appealing new findings of magnetic domain wall pile-up mechanism. • Overcome the limitations of materials properties for domain wall-based devices.
Far- and near-field second harmonic imaging of ferroelectric domain walls
DEFF Research Database (Denmark)
Bozhevolnyi, Sergey I.; Pedersen, Kjeld; Skettrup, Torben
1998-01-01
Domain walls in periodically poled ferroelectric LiNbO3 crystals are observed with both far- and near-field imaging techniques that make use of second harmonic generation in the transition regions between neighbouring domains. Second harmonic images of domain walls represent bright lines of about.......5 micrometers in width (as measured with the near-field microscope) for the polarization of the second harmonic radiation perpendicular to the domain walls. Origin and selection rules for the constrast in second harmonic images of domain walls are discussed....
The drift of ab-type domain walls in the weak ferromagnetic
Gerasimchuk, V S
2002-01-01
The drift motion of a ab-type 180-degree domain wall in a weak ferromagnetic is studied in elastic stress fields, generated by a sound wave. Parallel or perpendicularly to the domain wall plane. The dependences of the drift velocity on direction, polarization and amplitude of the acoustic wave are obtained. The drift conditions of the band domain structure are defined.
Charm Physics with Domain Wall Fermions and Physical Pion Masses
Boyle, Peter; Jüttner, Andreas; Khamseh, Ava; Sanfilippo, Francesco; Tsang, Justus Tobias; Witzel, Oliver
2016-01-01
We present RBC/UKQCD's charm project using $N_f=2+1$ flavour ensembles with inverse lattice spacings in the range $1.73-2.77\\,\\mathrm{GeV}$ and two physical pion mass ensembles. Domain wall fermions are used for the light as well as the charm quarks. We discuss our strategy for the extraction of the decay constants $f_D$ and $f_{D_s}$ and their extrapolation to the continuum limit, physical pion masses and the physical heavy quark mass. Our preliminary results are $f_D=208.7(2.8)\\,\\mathrm{MeV}$ and $f_{D_s}=246.4(1.9)\\,\\mathrm{MeV}$ where the quoted error is statistical only. We outline our current approach to extend the reach in the heavy quark mass and present preliminary results.
BPS domain walls in N=4 supergravity and dual flows
Cassani, Davide; Faedo, Anton F
2012-01-01
We establish the conditions for supersymmetric domain wall solutions to N=4 gauged supergravity in five dimensions. These read as BPS first-order equations for the warp factor and the scalar fields, driven by a superpotential and supplemented by a set of constraints that we specify in detail. Then we apply our results to certain consistent truncations of IIB supergravity, thus exploring their dual field theory renormalization group flows. We find a universal flow deforming superconformal theories on D3-branes at Calabi-Yau cones. Moreover, we obtain a superpotential for the solution corresponding to the baryonic branch of the Klebanov-Strassler theory, as well as the superpotential for the flow describing D3 and wrapped D5-branes on the resolved conifold.
Investigation of dominant spin wave modes by domain walls collision
Energy Technology Data Exchange (ETDEWEB)
Ramu, M.; Purnama, I.; Goolaup, S.; Chandra Sekhar, M.; Lew, W. S., E-mail: wensiang@ntu.edu.sg [School of Physical and Mathematical Sciences, Nanyang Technological University, 21 Nanyang Link, Singapore 637371 (Singapore)
2014-06-28
Spin wave emission due to field-driven domain wall (DW) collision has been investigated numerically and analytically in permalloy nanowires. The spin wave modes generated are diagonally symmetric with respect to the collision point. The non-propagating mode has the highest amplitude along the middle of the width. The frequency of this mode is strongly correlated to the nanowire geometrical dimensions and is independent of the strength of applied field within the range of 0.1 mT to 1 mT. For nanowire with film thickness below 5 nm, a second spin wave harmonic mode is observed. The decay coefficient of the spin wave power suggests that the DWs in a memory device should be at least 300 nm apart for them to be free of interference from the spin waves.
Depinning of domain walls in permalloy nanowires with asymmetric notches
Gao, Y.; You, B.; Ruan, X. Z.; Liu, M. Y.; Yang, H. L.; Zhan, Q. F.; Li, Z.; Lei, N.; Zhao, W. S.; Pan, D. F.; Wan, J. G.; Wu, J.; Tu, H. Q.; Wang, J.; Zhang, W.; Xu, Y. B.; Du, J.
2016-09-01
Effective control of the domain wall (DW) motion along the magnetic nanowires is of great importance for fundamental research and potential application in spintronic devices. In this work, a series of permalloy nanowires with an asymmetric notch in the middle were fabricated with only varying the width (d) of the right arm from 200 nm to 1000 nm. The detailed pinning and depinning processes of DWs in these nanowires have been studied by using focused magneto-optic Kerr effect (FMOKE) magnetometer, magnetic force microscopy (MFM) and micromagnetic simulation. The experimental results unambiguously exhibit the presence of a DW pinned at the notch in a typical sample with d equal to 500 nm. At a certain range of 200 nm notch, resulting in two DW depinning fields. Those two depinning fields have opposite d dependences, which may be originated from different potential well/barrier generated by the asymmetric notch with varying d.
Current-induced domain wall motion in ferromagnetic semiconductors
Ohno, Hideo
2007-03-01
Low magnetization (˜0.05 T) and high spin-polarization in ferromagnetism of transition metal-doped GaAs allow us to explore a number of spin-dependent phenomena not readily accessible in metal ferromagnets. Spin-polarized current induced domain wall (DW) motion in (Ga,Mn)As [1, 2] reveals rich physics resulting from the interaction between spin-polarized electrons and localized spins inside a magnetic DW. By using a 30 nm thick (Ga,Mn)As layer (xMn = 0.045) with perpendicular magnetic anisotropy, we have measured by magneto-optical Kerr microscopy a wide range of velocity-current density curves in the sample temperature range of 97 -- 107 K. Two regimes are found in the current density dependence of the DW velocity. At high-current densities (> 2 x 10^5 A/cm^2), the domain wall velocity is approximately a linear function of the current density above a threshold current density. This result will be compared to the recent theories of DW motion. At low-current densities, the functional form of the velocity-current curves follow an empirical scaling law, obtained by modifying the one for magnetic-field induced creep. This shows that current-induced DW creep is present. We have also determined the intrinsic resistance of the DW in a similar configuration [3]. *M. Yamanouchi, D. Chiba, F. Matsukura, and H. Ohno, Nature 428, 539 (2004). *M. Yamanouchi, D. Chiba, F. Matsukura, T. Dietl and H. Ohno, Phys. Rev. Lett. 96, 096601 (2006). *D. Chiba, M. Yamanouchi, F. Matsukura, T. Dietl, and H. Ohno, Phys. Rev. Lett. 96, 096602 (2006).
Angular Magnetoresistance of Nanowires with Alternating Cobalt and Nickel Segments
Mohammed, Hanan
2017-06-22
Magnetization reversal in segmented Co/Ni nanowires with varying number of segments was studied using angular Magnetoresistance (MR) measurements on isolated nanowires. The MR measurements offer an insight into the pinning of domain walls within the nanowires. Angular MR measurements were performed on nanowires with two and multiple segments by varying the angle between the applied magnetic field and nanowire (−90° ≤θ≤90°). The angular MR measurements reveal that at lower values of θ the switching fields are nearly identical for the multisegmented and two-segmented nanowires, whereas at higher values of θ, a decrease in the switching field is observed in the case of two segmented nanowires. The two segmented nanowires generally exhibit a single domain wall pinning event, whereas an increased number of pinning events are characteristic of the multisegmented nanowires at higher values of θ. In-situ magnetic force microscopy substantiates reversal by domain wall nucleation and propagation in multisegmented nanowires.
Measurement of magnetic domain wall width using energy-filtered Fresnel images.
Lloyd, S J; Loudon, J C; Midgley, P A
2002-08-01
Magnetic domain walls in Nd2Fe14B have been examined using a series of energy-filtered Fresnel images in the field emission gun transmission electron microscope (FEGTEM). We describe the changes in the intensity distribution of the convergent wall image as a function of defocus, foil thickness and domain wall width. The effect of tilted domain walls and beam convergence on the fringe pattern is also discussed. A comparison of the experimental intensity profile with that from simulations allows the domain wall width to be determined. Measurement of very narrow walls is made possible only by using a relatively thick foil, which necessitates energy-filtering to allow quantitative comparison with simulations. The magnetic domain wall width in Nd2Fe14B was found to be 3 +/- 2 nm.
Electric field induced domain-wall dynamics: Depinning and chirality switching
Upadhyaya, Pramey; Dusad, Ritika; Hoffman, Silas; Tserkovnyak, Yaroslav; Alzate, Juan G.; Amiri, Pedram Khalili; Wang, Kang L.
2013-12-01
We theoretically study the equilibrium and dynamic properties of nanoscale magnetic tunnel junctions (MTJs) and magnetic wires, in which an electric field controls the magnetic anisotropy through spin-orbit coupling. By performing micromagnetic simulations, we construct a rich phase diagram and find that, in particular, the equilibrium magnetic textures can be tuned between Néel and Bloch domain walls in an elliptical MTJ. Furthermore, we develop a phenomenological model of a quasi-one-dimensional domain wall confined by a parabolic potential and show that, near the Néel-to-Bloch-wall transition, a pulsed electric field induces precessional domain-wall motion which can be used to reverse the chirality of a Néel wall and even depin it. This domain-wall motion controlled by electric fields, in lieu of applied current, may provide a model for ultralow-power domain-wall memory and logic devices.
Coupled Néel domain wall motion in sandwiched perpendicular magnetic anisotropy nanowires.
Purnama, I; Kerk, I S; Lim, G J; Lew, W S
2015-03-04
The operating performance of a domain wall-based magnetic device relies on the controlled motion of the domain walls within the ferromagnetic nanowires. Here, we report on the dynamics of coupled Néel domain wall in perpendicular magnetic anisotropy (PMA) nanowires via micromagnetic simulations. The coupled Néel domain wall is obtained in a sandwich structure, where two PMA nanowires that are separated by an insulating layer are stacked vertically. Under the application of high current density, we found that the Walker breakdown phenomenon is suppressed in the sandwich structure. Consequently, the coupled Néel domain wall of the sandwich structure is able to move faster as compared to individual domain walls in a single PMA nanowire.
Energy Technology Data Exchange (ETDEWEB)
Alija, A; Sobrado, I; Rodriguez-RodrIguez, G; Velez, M; Alameda, J M; MartIn, J I [Dpto. Fisica. Fac. Ciencias. Universidad de Oviedo - CINN. 33007, Oviedo (Spain); Parrondo, J M R, E-mail: a.alija@cinn.e [Dpto. Fisica Atomica, Molecular y Nuclear and GISD. Universidad Complutense de Madrid. 28040, Madrid (Spain)
2010-01-01
Micromagnetic simulations have been performed in uniaxial magnetic films with 2D array of asymmetric arrow shape holes. In order to understand the asymmetric pinning potential created by the holes, different boundary geometries conditions are used on the simulations. The depinning fields for forward and backward domain wall propagation have been calculated by the analysis of the energy landscapes as a function of the domain wall position. Domain wall depinning occurs preferentially at the free ends of the domain wall at the film boundaries. We have found that the domain wall propagation is different at the top/bottom boundaries of the simulated film which can be understood in terms of the magnetostatic energy and the chirality of the domain wall.
Current-driven dynamics of chiral ferromagnetic domain walls.
Emori, Satoru; Bauer, Uwe; Ahn, Sung-Min; Martinez, Eduardo; Beach, Geoffrey S D
2013-07-01
In most ferromagnets the magnetization rotates from one domain to the next with no preferred handedness. However, broken inversion symmetry can lift the chiral degeneracy, leading to topologically rich spin textures such as spin spirals and skyrmions through the Dzyaloshinskii-Moriya interaction (DMI). Here we show that in ultrathin metallic ferromagnets sandwiched between a heavy metal and an oxide, the DMI stabilizes chiral domain walls (DWs) whose spin texture enables extremely efficient current-driven motion. We show that spin torque from the spin Hall effect drives DWs in opposite directions in Pt/CoFe/MgO and Ta/CoFe/MgO, which can be explained only if the DWs assume a Néel configuration with left-handed chirality. We directly confirm the DW chirality and rigidity by examining current-driven DW dynamics with magnetic fields applied perpendicular and parallel to the spin spiral. This work resolves the origin of controversial experimental results and highlights a new path towards interfacial design of spintronic devices.
Interaction between a domain wall and spin supercurrent in easy-cone magnets
Kim, Se Kwon; Tserkovnyak, Yaroslav
2016-12-01
A domain wall and spin supercurrent can coexist in magnets with easy-cone anisotropy owing to simultaneous spontaneous breaking of Z2 and U(1) symmetries. Their interaction is theoretically investigated in quasi-one-dimensional ferromagnets within the Landau-Lifshitz-Gilbert phenomenology. Specifically, the spin supercurrent can exert the torque on a domain wall and thereby drive it. We also show, as a reciprocal phenomenon, a field-induced motion of a domain wall can generate spin supercurrent.
Domain walls collision in Fe-rich and Co-rich glass covered microwires
Directory of Open Access Journals (Sweden)
Gonzalez J.
2013-01-01
Full Text Available We report the results of the investigation of domain walls propagation in Fe-rich and Co-rich microwires performed using Sixtus-Tonks and magneto-optical Kerr effect techniques. It was found that under certain experimental conditions we are able to create the regime of the motion of two domain walls moving to opposite directions which terminates by the collision of the domain walls. Also the domain walls collision was visualized using magneto-optical Kerr effect microscope when the surface giant Barkhausen jump induced by circular magnetic field has been observed.
Magnetic soft x-ray microscopy of the domain wall depinning process in permalloy magnetic nanowires.
Im, Mi-Young; Bocklage, Lars; Meier, Guido; Fischer, Peter
2012-01-18
Full-field magnetic transmission x-ray microscopy at high spatial resolution down to 20 nm is used to directly observe field-driven domain wall motion in notch-patterned permalloy nanowires. The depinning process of a domain wall around a notch exhibits a stochastic nature in most nanowires. The stochasticity of the domain wall depinning sensitively depends on the geometry of the nanowire such as the wire thickness, the wire width, and the notch depth. We propose an optimized design of the nanowire for deterministic domain wall depinning field at a notch.
Vogel, J; Bonfim, M; Rougemaille, N; Boulle, O; Miron, I M; Auffret, S; Rodmacq, B; Gaudin, G; Cezar, J C; Sirotti, F; Pizzini, S
2012-06-15
Domain wall motion induced by nanosecond current pulses in nanostripes with perpendicular magnetic anisotropy (Pt/Co/AlO(x)) is shown to exhibit negligible inertia. Time-resolved magnetic microscopy during current pulses reveals that the domain walls start moving, with a constant speed, as soon as the current reaches a constant amplitude, and no or little motion takes place after the end of the pulse. The very low "mass" of these domain walls is attributed to the combination of their narrow width and high damping parameter α. Such a small inertia should allow accurate control of domain wall motion by tuning the duration and amplitude of the current pulses.
Injection and controlled motion of conducting domain walls in improper ferroelectric Cu-Cl boracite
McQuaid, Raymond G. P.; Campbell, Michael P.; Whatmore, Roger W.; Kumar, Amit; Gregg, J. Marty
2017-05-01
Ferroelectric domain walls constitute a completely new class of sheet-like functional material. Moreover, since domain walls are generally writable, erasable and mobile, they could be useful in functionally agile devices: for example, creating and moving conducting walls could make or break electrical connections in new forms of reconfigurable nanocircuitry. However, significant challenges exist: site-specific injection and annihilation of planar walls, which show robust conductivity, has not been easy to achieve. Here, we report the observation, mechanical writing and controlled movement of charged conducting domain walls in the improper-ferroelectric Cu3B7O13Cl. Walls are straight, tens of microns long and exist as a consequence of elastic compatibility conditions between specific domain pairs. We show that site-specific injection of conducting walls of up to hundreds of microns in length can be achieved through locally applied point-stress and, once created, that they can be moved and repositioned using applied electric fields.
Modeling thermally activated domain wall dynamics in thin magnetic strips with disorder
Energy Technology Data Exchange (ETDEWEB)
Laurson, L; Mughal, A; Serpico, C; Durin, G; Zapperi, S, E-mail: lasse.laurson@gmail.com [ISI Foundation, Torino (Italy)
2011-04-01
We study the effect of disorder and temperature on the field-driven dynamics of a transverse domain wall occurring in thin and narrow magnetic strips made of a soft magnetic material such as permalloy. Motivated by a micromagnetic description of such a domain wall, we construct a model based on two coupled flexible lines enclosing the domain wall transition region, capturing both the finite width and the characteristic V-shape of the wall. Disorder is included via randomly distributed pinning centers interacting with the two lines. We study the field-driven dynamics of the domain wall in disordered strips in a finite temperature, and compare our findings to experimental observations of stochastic domain wall dynamics.
Correlated Switching Dynamics in the Nanoscale Proximity of 90∘ Ferroelectric Domain Walls
Lei, Shiming; Wang, Xueyun; Cheong, S. W.; Chen, L. Q.; Kalinin, Sergei; Gopalan, Venkatraman
2015-03-01
Ferroelectrics are materials which have a built in polarization in their crystal structure even in the absence of an electric field. Domain walls themselves can possess dramatically different properties than the bulk ferroelectrics themselves. Previously we discovered that the universally present 180° walls have an order of magnitude lower domain switching threshold field than the bulk. This effect extends up to many microns around a wall, though the wall itself is unit cell thick. Here we present new results on 90° walls in PbTiO3 single crystals that show similar proximity effect and correlated switching. Our SSPFM imaging across the a / c / a domain walls suggests a strong correlated switching behavior in the proximity of the inclined 90° domain walls, even at a small AC driving voltage of 1V without DC bias on the tip. Consistent with phase-field modeling results, the inclined extended domain walls is found to act as nucleation sites in ferroelectric materials, and give rise to the domain wall asymmetrical broadening across the domain wall.
Transverse field-induced nucleation pad switching modes during domain wall injection
Energy Technology Data Exchange (ETDEWEB)
Bryan, M. T.; Fry, P. W.; Schrefl, T.; Gibbs, M. R. J.; Allwood, D. A.; Im, M.-Y.; Fischer, P.
2010-03-12
We have used magnetic transmission X-ray microscopy (M-TXM) to image in-field magnetization configurations of patterned Ni{sub 80}Fe{sub 20} domain wall 'injection pads' and attached planar nanowires. Comparison with micromagnetic simulations suggests that the evolution of magnetic domains in rectangular injection pads depends on the relative orientation of closure domains in the remanent state. The magnetization reversal pathway is also altered by the inclusion of transverse magnetic fields. These different modes explain previous results of domain wall injection into nanowires. Even more striking was the observation of domain walls injecting halfway across the width of wider (>400 nm wide) wires but over wire lengths of several micrometers. These extended Neel walls can interact with adjacent nanowires and cause a switching in the side of the wire undergoing reversal as the domain wall continues to expand.
Temperature-dependent anisotropic magnetoresistance inversion behaviors in Fe3O4 films
Yoon, Kap Soo; Hong, Jin Pyo
2017-02-01
We address the abnormal anisotropic magnetoresistance (AMR) reversal feature of half-metallic polycrystalline Fe3O4 films occurring at a specific temperature. Experimental results revealed a positive to negative MR transition in the Fe3O4 films at 264 K, which reflect the influence of additional domain wall scattering. These features was described by a correlation between domain wall resistance and inversion behavior of AMR with additional domain wall scattering factors. We further describe a possible model based on systematic structural and electrical measurements that employs a temperature-dependent domain wall width and spin diffusion length of the conducting electrons. This model allows for spin-flipping scattering of spin polarized electrons inside a proper domain width.
Evidence of domain wall pinning in aluminum substituted cobalt ferrites
Maurya, J. C.; Janrao, P. S.; Datar, A. A.; Kanhe, N. S.; Bhoraskar, S. V.; Mathe, V. L.
2016-08-01
In the present work spinel structured cobalt ferrites with aluminum substitution having composition CoAlxFe2-xO4 (x=0.0, 0.1, 0.2 and 0.3) have been synthesized using chemical co-precipitation method. Their microstructural, magnetic, magnetostriction and magnetoimpedance properties have been investigated. The piezomagnetic coefficient (dλ/dH) obtained from magnetostriction data is found to enhance with 0.1 Al substitutions in place of iron which decreases with further increase of Al content. It is noticed that 0.3 Al substitutions in place of Fe introduces domain wall pinning as evidenced from magnetostriction, magnetoimpedance and dc magnetization data. It is noted that ferrites so prepared using a simple procedure are magnetostrictive in good measure and with the addition of very small amount of non-magnetic aluminum their magnetostriction has shown saturation at relatively low magnetic fields. Such magnetostrictive ferrites find their applications in magnetic sensors and actuators.
Domain walls and vortices in linearly coupled systems
Dror, Nir; Zeng, Jianhua
2011-01-01
We investigate 1D and 2D radial domain-wall (DW) states in the system of two nonlinear-Schr\\"{o}dinger/Gross-Pitaevskii equations, which are coupled by the linear mixing and by the nonlinear XPM (cross-phase-modulation). The system has straightforward applications to two-component Bose-Einstein condensates, and to the bimodal light propagation in nonlinear optics. In the former case, the two components represent different hyperfine atomic states, while in the latter setting they correspond to orthogonal polarizations of light. Conditions guaranteeing the stability of flat continuous wave (CW) asymmetric bimodal states are established, followed by the study of families of the corresponding DW patterns. Approximate analytical solutions for the DWs are found near the point of the symmetry-breaking bifurcation of the CW states. An exact DW solution is produced for ratio 3:1 of the XPM and SPM coefficients. The DWs between flat asymmetric states, which are mirror images to each other, are completely stable, and al...
Magnetic domain wall motion in notch patterned permalloy nanowire devices
Energy Technology Data Exchange (ETDEWEB)
Chen, Ting-Chieh; Kuo, Cheng-Yi; Mishra, Amit K.; Das, Bipul; Wu, Jong-Ching, E-mail: phjcwu@cc.ncue.edu.tw
2015-11-01
We report a study of magnetization reversal process of notch-patterned permalloy (Py) nanowires (NWs) by using an in-situ magnetic force microscopy (MFM). Three neighboring straight NWs and an individual straight NW with discs connected to the wires ends are fabricated by standard electron beam lithography through a lift-off technique. MFM images are taken in the presence of an in-plane magnetic field applied along the wires length. As a result, the nucleation, pinning and depinning of domain walls (DWs) along the NW are observed. The artificial constraints (notch) in such symmetrical geometry of NWs indeed serve as pinning sites to pin the DWs. The nature of magnetization reversal, pinning field and depinning field for the DWs that are observed in these permalloy NWs, indicate the key roles of notch depth, the terminal connection structure of NW end and the inter-wire interaction among the NWs. The in-situ MFM measurements are examined with the micromagnetic simulations. Consequently, good agreements are obtained for the DW structures and the effect of DWs pining/depinning, however a dissimilarity in experimental and simulation observations for the direction of propagation of DWs in NWs needs further investigation.
Charm as a domain wall fermion in quenched lattice QCD
Lin, H W; Soni, A; Yamada, N; Lin, Huey-Wen; Ohta, Shigemi; Soni, Amarjit; Yamada, Norikazu
2006-01-01
We report a study describing the charm quark by a domain-wall fermion (DWF) in lattice quantum chromodynamics (QCD). Our study uses a quenched gauge ensemble with the DBW2 rectangle-improved gauge action at a lattice cutoff of $a^{-1} \\sim 3$ GeV. We calculate masses of heavy-light (charmed) and heavy-heavy (charmonium) mesons with spin-parity $J^P = 0^\\mp$ and $1^\\mp$, leptonic decay constants of the charmed pseudoscalar mesons ($D$ and $D_s$), and the $D^0$-$\\bar{D^0}$ mixing parameter. The charm quark mass is found to be $m^{\\bar{\\rm MS}}_{c}(m_{c})=1.24(1)(18)$ GeV. The mass splittings in charmed-meson parity partners $\\Delta_{q,J=0}$ and $\\Delta_{q, J=1}$ are degenerate within statistical errors, in accord with experiment, and they satisfy a relation $\\Delta_{q=ud, J} > \\Delta_{q=s, J}$, also consistent with experiment. A C-odd axial vector charmonium state, $h_c), lies 22(11) MeV above the $\\chi_{c1}$ meson, or $m_{h_{c}} = 3533(11)_{\\rm stat.}$ MeV using the experimental $\\chi_{c1}) mass. However, in t...
Spin torque and domain wall velocity in ferromagnetic semiconductor π and 2π N'eel walls
Golovatski, E. A.; Flatté, M. E.
2010-03-01
The motion of a domain wall under an applied spin-polarized current[1] has interesting device applications for the development of spintronic devices. We model 2π N'eel walls (energetically favorable in thin films) in ferromagnetic semiconductors, and compare the results to those for the more-frequently studied π walls. Under coherent transport conditions, analytic solutions for spin-dependent reflection and transmission coefficients are possible[2,3]. We calculate charge resistance, spin torque, and domain wall velocity. We find the peak spin torque is more than twice as large for a 2π wall than for a π wall. We also find that the peak velocity of a 2π wall is larger than that of a π wall, but the peak velocities of 3π and 4π walls are smaller than those of both π and 2π walls. This work was supported by an ARO MURI.[4pt] [1] M. Yamanouchi, D. Chiba, F. Matsukura, and H. Ohno, Nature 428, 539 (2004).[0pt] [2] G. Vignale and M. Flatt'e, Phys. Rev. Lett. 89 (2002).[0pt] [3] D. Ralph and M. Stiles, Journal of Magnetism and Magnetic Materials 320, 1190 (2008).
Domain walls to Boussinesq-type equations in (2 + 1)-dimensions
Triki, H.; Kara, A. H.; Biswas, A.
2014-07-01
In this paper, two models with fourth-order dispersion in 2 + 1 dimensions are investigated. Based on Ansatz method, exact domain wall solutions are derived. Parametric conditions for the existence of the domain wall solutions are given. Lie symmetry analysis also retrieves conserved densities of governing nonlinear evolution equations.
Creep of current-driven domain-wall lines: intrinsic versus extrinsic pinning
Duine, R.A.; de Morais Smith, C.
2008-01-01
We present a model for current-driven motion of a magnetic domain-wall line, in which the dynamics of the domain wall is equivalent to that of an overdamped vortex line in an anisotropic pinning potential. This potential has both extrinsic contributions due to, e.g., sample inhomogeneities, and an
Exact solution of eddy current losses produced by a domain wall with nonzero thickness
Energy Technology Data Exchange (ETDEWEB)
Real, R.P. del [Laboratorio de Optoelectronica, Area de Cargas Utiles e Instrumentacion, Departamento de Ciencias del Espacio y Tecnologias Electronicas, Instituto Nacional de Tecnica Aeroespacial (INTA), Torrejon de Ardoz 28850 (Spain)]. E-mail: perezrr@inta.es
2006-08-15
The influence of the domain wall thickness on eddy current losses has been calculated. It is shown that, for samples with low magnetic anisotropy and small thickness, the reduction of magnetic losses with respect to the zero thickness domain wall must be seriously taken into account.
Current-driven vortex domain wall motion in wire-tube nanostructures
Energy Technology Data Exchange (ETDEWEB)
Espejo, A. P. [Departamento de Física, Universidad de Santiago de Chile (USACH), Av. Ecuador 3493, 9170124 Santiago (Chile); Institute of Nanostructure and Solid State Physics, University of Hamburg, Jungiusstrasse 11, D-20355 Hamburg (Germany); Vidal-Silva, N. [Departamento de Física, Universidad de Santiago de Chile (USACH), Av. Ecuador 3493, 9170124 Santiago (Chile); López-López, J. A. [Departamento de Física, Universidad Técnica Federico Santa María, Av. España 1680, Valparaíso (Chile); Goerlitz, D.; Nielsch, K. [Institute of Nanostructure and Solid State Physics, University of Hamburg, Jungiusstrasse 11, D-20355 Hamburg (Germany); Escrig, J. [Departamento de Física, Universidad de Santiago de Chile (USACH), Av. Ecuador 3493, 9170124 Santiago (Chile); Center for the Development of Nanoscience and Nanotechnology (CEDENNA), Av. Ecuador 3493, 9170124 Santiago (Chile)
2015-03-30
We have investigated the current-driven domain wall motion in nanostructures comprised of a pair of nanotube and nanowire segments. Under certain values of external magnetic fields, it is possible to pin a vortex domain wall in the transition zone between the wire and tube segments. We explored the behavior of this domain wall under the action of an electron flow applied in the opposite direction to the magnetic field. Thus, for a fixed magnetic field, it is possible to release a domain wall pinned simply by increasing the intensity of the current density, or conversely, for a fixed current density, it is possible to release the domain wall simply decreasing the magnetic external field. When the domain wall remains pinned due to the competition between the current density and the magnetic external field, it exhibits a oscillation frequency close to 8 GHz. The amplitude of the oscillations increases with the current density and decreases over time. On the other hand, when the domain wall is released and propagated through the tube segment, this shows the standard separation between a steady and a precessional regime. The ability to pin and release a domain wall by varying the geometric parameters, the current density, or the magnetic field transforms these wire-tube nanostructures in an interesting alternative as an on/off switch nano-transistor.
Energy Technology Data Exchange (ETDEWEB)
Lequeux, Steven; Sampaio, Joao; Bortolotti, Paolo; Cros, Vincent; Grollier, Julie [Unité Mixte de Physique CNRS/Thales and Université Paris-Sud 11, 1 Ave. A. Fresnel, 91767 Palaiseau (France); Devolder, Thibaut [Institut d' Electronique Fondamentale, Univ. Paris-Sud, CNRS UMR 8622, Bât. 220, 91405 Orsay Cedex (France); Matsumoto, Rie; Yakushiji, Kay; Kubota, Hitoshi; Fukushima, Akio; Yuasa, Shinji [National Institute of Advanced Industrial Science and Technology (AIST), 1-1-1 Umezono, Tsukuba, Ibaraki 305-8568 (Japan); Nishimura, Kazumasa; Nagamine, Yoshinori; Tsunekawa, Koji [Process Development Center, Canon ANELVA Corporation, Kurigi 2-5-1, Asao, Kawasaki, Kanagawa 215-8550 (Japan)
2015-11-02
Spin torque resonance has been used to simultaneously probe the dynamics of a magnetic domain wall and of magnetic domains in a nanostripe magnetic tunnel junction. Due to the large associated resistance variations, we are able to analyze quantitatively the resonant properties of these single nanoscale magnetic objects. In particular, we find that the magnetic damping of both the domains and the domain wall is doubled compared to the damping value of the host magnetic layer. We estimate the contributions to the damping arising from the dipolar couplings between the different layers in the junction and from the intralayer spin pumping effect, and find that they cannot explain the large damping enhancement that we observe. We conclude that the measured increased damping is intrinsic to large amplitudes excitations of spatially localized modes or solitons such as vibrating or propagating domain walls.
Modulated Magnetic Nanowires for Controlling Domain Wall Motion: Toward 3D Magnetic Memories
Ivanov, Yurii P.
2016-05-03
Cylindrical magnetic nanowires are attractive materials for next generation data storage devices owing to the theoretically achievable high domain wall velocity and their efficient fabrication in highly dense arrays. In order to obtain control over domain wall motion, reliable and well-defined pinning sites are required. Here, we show that modulated nanowires consisting of alternating nickel and cobalt sections facilitate efficient domain wall pinning at the interfaces of those sections. By combining electron holography with micromagnetic simulations, the pinning effect can be explained by the interaction of the stray fields generated at the interface and the domain wall. Utilizing a modified differential phase contrast imaging, we visualized the pinned domain wall with a high resolution, revealing its three-dimensional vortex structure with the previously predicted Bloch point at its center. These findings suggest the potential of modulated nanowires for the development of high-density, three-dimensional data storage devices. © 2016 American Chemical Society.
Current-driven magnetic domain wall motion and its real-time detection
Kim, Kab-Jin; Yoshimura, Yoko; Ono, Teruo
2017-08-01
Current-controlled magnetic domain wall motion has opened the possibility of a novel type of shift register memory device, which has been optimistically predicted to replace existing magnetic memories. Owing to this promising prospect, intensive work has been carried out during the last few decades. In this article, we first review the progress in the study of current-induced magnetic domain wall motion. Underlying mechanisms behind the domain wall motion, which have been discovered during last few decades, as well as technological achievements are presented. We then present our recent experimental results on the real-time detection of current-driven multiple magnetic domain wall motion, which directly demonstrates the operation of a magnetic domain wall shift register.
Magnetic Domain Walls as Hosts of Spin Superfluids and Generators of Skyrmions
Kim, Se Kwon; Tserkovnyak, Yaroslav
2017-07-01
A domain wall in a magnet with easy-axis anisotropy is shown to harbor spin superfluid associated with its spontaneous breaking of the U(1) spin-rotational symmetry. The spin superfluid is shown to have several topological properties, which are absent in conventional superfluids. First, the associated phase slips create and destroy Skyrmions to obey the conservation of the total Skyrmion charge, which allows us to use a domain wall as a generator and detector of Skyrmions. Second, the domain wall engenders the emergent magnetic flux for magnons along its length, which are proportional to the spin supercurrent flowing through it, and thereby provides a way to manipulate magnons. Third, the spin supercurrent can be driven by the magnon current traveling across it owing to the spin transfer between the domain wall and magnons, leading to the magnonic manipulation of the spin superfluid. The theory for superfluid spin transport within the domain wall is confirmed by numerical simulations.
Athermal domain-wall creep near a ferroelectric quantum critical point.
Kagawa, Fumitaka; Minami, Nao; Horiuchi, Sachio; Tokura, Yoshinori
2016-02-16
Ferroelectric domain walls are typically stationary because of the presence of a pinning potential. Nevertheless, thermally activated, irreversible creep motion can occur under a moderate electric field, thereby underlying rewritable and non-volatile memory applications. Conversely, as the temperature decreases, the occurrence of creep motion becomes less likely and eventually impossible under realistic electric-field magnitudes. Here we show that such frozen ferroelectric domain walls recover their mobility under the influence of quantum fluctuations. Nonlinear permittivity and polarization-retention measurements of an organic charge-transfer complex reveal that ferroelectric domain-wall creep occurs via an athermal process when the system is tuned close to a pressure-driven ferroelectric quantum critical point. Despite the heavy masses of material building blocks such as molecules, the estimated effective mass of the domain wall is comparable to the proton mass, indicating the realization of a ferroelectric domain wall with a quantum-particle nature near the quantum critical point.
Reply to "Domain-growth kinetics of systems with soft walls''
DEFF Research Database (Denmark)
Mouritsen, Ole G.; Præstgaard, Eigil
1988-01-01
On the basis of computer-simulation results for three different models with soft domain walls it is argued that the zero-temperature domain-growth kinetics falls in a separate universality class characterized by a kinetic growth exponent n≃0.25. However, for finite temperatures there is a distinct...... crossover to Lifshitz-Allen-Cahn kinetics n=0.50, thus suggesting that the soft-wall and hard-wall universality classes become identical at finite temperatures....
Soft-wall domain-growth kinetics of twofold-degenerate ordering
DEFF Research Database (Denmark)
Mouritsen, Ole G.
1986-01-01
The domain growth in a two-dimensional twofold-degenerate system with soft domain walls is shown to obey dynamical scaling. The value of the growth exponent is n≃0.25 which differs from the classical Lifshitz-Allen-Cahn prediction n=(1/2), but accords with recent findings for other growth models ...... with soft walls. The results suggest that domain-wall softness may be more important than the degeneracy of the ground state for a possible universal classification of domain-growth kinetics....
Enhancement of Local Photovoltaic Current at Ferroelectric Domain Walls in BiFeO3
Yang, Ming-Min; Bhatnagar, Akash; Luo, Zheng-Dong; Alexe, Marin
2017-02-01
Domain walls, which are intrinsically two dimensional nano-objects exhibiting nontrivial electronic and magnetic behaviours, have been proven to play a crucial role in photovoltaic properties of ferroelectrics. Despite this recognition, the electronic properties of domain walls under illumination until now have been accessible only to macroscopic studies and their effects upon the conduction of photovoltaic current still remain elusive. The lack of understanding hinders the developing of nanoscale devices based on ferroelectric domain walls. Here, we directly characterize the local photovoltaic and photoconductive properties of 71° domain walls on BiFeO3 thin films with a nanoscale resolution. Local photovoltaic current, proven to be driven by the bulk photovoltaic effect, has been probed over the whole illuminated surface by using a specially designed photoelectric atomic force microscopy and found to be significantly enhanced at domain walls. Additionally, spatially resolved photoconductive current distribution reveals a higher density of excited carriers at domain walls in comparison with domains. Our measurements demonstrate that domain wall enhanced photovoltaic current originates from its high conduction rather than the internal electric field. This photoconduction facilitated local photovoltaic current is likely to be a universal property of topological defects in ferroelectric semiconductors.
DEFF Research Database (Denmark)
Mouritsen, Ole G.; Praestgaard, Eigil
1988-01-01
temperature, the domain-growth kinetics is found to be independent of the value of this parameter over several decades of its range. This suggests that a universal principle is operative. The domain-wall shape is analyzed and shown to be well represented by a hyperbolic tangent function. The growth process......The domain-growth kinetics in two different anisotropic two-dimensional XY-spin models is studied by computer simulation. The models have uniaxial and cubic anisotropy which leads to ground-state orderings which are twofold and fourfold degenerate, respectively. The models are quenched from...... infinite to zero temperature as well as to nonzero temperatures below the ordering transition. The continuous nature of the spin variables causes the domain walls to be ‘‘soft’’ and characterized by a finite thickness. The steady-state thickness of the walls can be varied by a model parameter, P. At zero...
Energy Technology Data Exchange (ETDEWEB)
Kravchuk, Volodymyr P., E-mail: vkravchuk@bitp.kiev.ua
2014-10-01
It is shown that the Dzialoshinskii–Moriya interaction leads to asymmetrical deformation of the transverse domain wall profile in one-dimensional biaxial magnet. Amplitude of the deformation is linear with respect to the Dzialoshinskii constant D. Corrections caused by the Dzialoshinskii–Moriya interaction are obtained for the number of the domain wall parameters: energy density, Döring mass, and Walker field. The modified q–Φ model with an additional pair of conjugated collective variables is proposed for studying the dynamical properties of the wall with taking into account the internal degrees of freedom. - Highlights: • Dzialoshinskii–Moriya interaction deforms the domain wall profile asymmetrically. • Extended model with 2 pairs of collective variables is proposed for a domain wall. • The Walker field is slightly changed due to the Dzialoshinskii–Moriya interaction.
Hydrodynamics of domain walls in ferroelectrics and multiferroics: Impact on memory devices
Scott, J. F.; Evans, D. M.; Gregg, J. M.; Gruverman, A.
2016-07-01
The standard "Kittel Law" for the thickness and shape of ferroelectric, ferroelastic, or ferromagnet domains assumes mechanical equilibrium. The present paper shows that such domains may be highly nonequilibrium, with unusual thicknesses and shapes. In lead germanate and multiferroic lead zirconate titanate iron tantalate domain wall instabilities resemble hydrodynamics (Richtmyer-Meshkov and Helfrich-Hurault, respectively).
Domain wall structure transition during magnetization reversal process in magnetic nanowires
Institute of Scientific and Technical Information of China (English)
无
2007-01-01
The analytical micromagnetics and numerical simulations were used to investigate the domain wall structure during the magnetization reversal in nanowires. Micromagnetic analysis shows that the domain wall structure is mainly determined by the competition between the demagnetization energy and exchange energy. The wall with vortex magnetization structure in cross-section is energetically more favorable for wires with large diameter. With the reduction of diameter the exchange energy increases. At a critical diameter the vortex structure can not be sustained and the transition from vortex wall to transverse wall occurs. The critical diameters for this transition are about 40 nm for Ni wire and 20 nm for Fe wire, respectively. A series of micromagnetic simulations on the cone-shaped wire confirm the analytical results. The simulations also show that during the reversal process the vortex domain wall moves much faster than the transverse one.
Domain wall network as QCD vacuum and the chromomagnetic trap formation under extreme conditions
Energy Technology Data Exchange (ETDEWEB)
Nedelko, Sergei N.; Voronin, Vladimir E. [JINR, Bogoliubov Laboratory of Theoretical Physics, Dubna (Russian Federation)
2015-04-01
The ensemble of Euclidean gluon field configurations represented by the domain wall network is considered. A single domain wall is given by the sine-Gordon kink for the angle between chromomagnetic and chromoelectric components of the gauge field. The domain wall separates the regions with Abelian self-dual and anti-self-dual fields. The network of the domain wall defects is introduced as a combination of multiplicative and additive superpositions of kinks. The character of the spectrum and eigenmodes of color-charged fluctuations in the presence of the domain wall network is discussed. Conditions for the formation of a stable thick domain wall junction (the chromomagnetic trap) during heavy-ion collisions are discussed, and the spectrum of color-charged quasi-particles inside the trap is evaluated. An important observation is the existence of the critical size L{sub c} of a single trap stable against gluon tachyonic modes. The size L{sub c} is related to the value of gluon condensate left angle g{sup 2} F{sup 2} right angle. The growth of large lumps of merged chromomagnetic traps and the concept of the confinement-deconfinement transition in terms of the ensemble of domain wall networks are outlined. (orig.)
Micromagnetic simulation of thickness variation of Neel cap in hybrid Bloch-Neel domain wall
Energy Technology Data Exchange (ETDEWEB)
Lu Mai [Key Lab. of Opto-Electronic Technology and Intelligent Control, Lanzhou Jiaotong University, Ministry of Education, P.O. Box 73, 118 West Anning Road, Lanzhou 730070, Gansu (China) and Department of Signals and Systems, Chalmers University of Technology, SE-412 96, Gothenburg (Sweden)]. E-mail: m.lu@mail.edu.cn; Leonard, Paul J. [Department of Electronic and Electrical Engineering, University of Bath, Claverton Down, Bath BA2 7AY (United Kingdom)
2005-08-01
The hybrid Bloch-Neel domain wall in iron film has been investigated using three-dimensional micromagnetic calculations. Magnetization distributions in the film plane and cross-section are presented. In the film plane the rotation of magnetization in the 180 deg domain wall takes two different patterns from the bottom layer to the top layer. In cross-section the C-shaped magnetization distribution with hybrid Bloch-Neel domain wall has been found. The thickness of the top Neel cap changes from its largest value as the C-shaped magnetization distribution appears, and becomes thinner as the C-shaped magnetization distribution gradually moves and grows up. The thickness variation of the bottom Neel cap changes in a similar way, but with a reversal pattern. The results in this paper will enrich our knowledge of magnetic domain and domain wall patterns in magnetic materials.
Domain wall energy landscapes in amorphous magnetic films with asymmetric arrays of holes
Energy Technology Data Exchange (ETDEWEB)
Alija, A; Perez-Junquera, A; RodrIguez-RodrIguez, G; Velez, M; Alameda, J M; MartIn, J I [Depto. Fisica, Fac. Ciencias, Universidad de Oviedo - CINN, Av. Calvo Sotelo s/n, 33007 Oviedo (Spain); Marconi, V I; Kolton, A B; Parrondo, J M R [Depto. Fisica Atomica, Molecular y Nuclear, and GISC, Universidad Complutense, 28040 Madrid (Spain); Anguita, J V [Instituto de Microelectronica de Madrid, CNM-CSIC, Isaac Newton 8, PTM, Tres Cantos, 28760 Madrid (Spain)
2009-02-21
Arrays of asymmetric holes have been defined in amorphous Co-Si films by e-beam lithography in order to study domain wall motion across the array subject to the asymmetric pinning potential created by the holes. Experimental results on Kerr effect magnetooptical measurements and hysteresis loops are compared with micromagnetic simulations in films with arrays of triangular holes. These show that the potential asymmetry favours forward wall propagation for flat walls but, if the wall contains a kink, net backward wall propagation is preferred at low fields, in agreement with minor loop experiments. The difference between the fields needed for forward and backward flat wall propagation increases as the size of the triangular holes is reduced, becoming maximum for 1 {mu}m triangles, which is the characteristic length scale set by domain wall width.
Domain walls in Fe(001) bicrystals-thickness dependence and field-induced transitions
Energy Technology Data Exchange (ETDEWEB)
Hanson, M. [Department of Applied physics, Chalmers University of Technology, SE-412 96 Goeteborg (Sweden)]. E-mail: maj.hanson@fy.chalmers.se; Brucas, R. [Department of Applied physics, Chalmers University of Technology, SE-412 96 Goeteborg (Sweden)
2007-03-15
Magnetic domain walls (DW's) formed at the grain boundary (GB) of epitaxial bicrystal Fe(001) films, thickness t=50 and 70nm, were studied by magnetic force microscopy. The 'as-grown' samples displayed DW's with different magnetic contrast profiles yielding a single peak for t=50nm and a double peak with a change of sign at the centre of the wall for t=70nm. For t=50nm the wall is characterised as an asymmetric Bloch wall. The double peak of the 70nm thick film transformed into a single peak characteristic for a charged wall, when a field of 30mT was applied along the GB. At remanence this domain wall relaxed to a regular Bloch wall divided into segments of alternating signs.
Domain wall motion driven by spin Hall effect—Tuning with in-plane magnetic anisotropy
Energy Technology Data Exchange (ETDEWEB)
Rushforth, A. W., E-mail: andrew.rushforth@nottingham.ac.uk [School of Physics and Astronomy, University of Nottingham, University Park, Nottingham NG7 2RD (United Kingdom)
2014-04-21
This letter investigates the effects of in-plane magnetic anisotropy on the current induced motion of magnetic domain walls in systems with dominant perpendicular magnetic anisotropy, where accumulated spins from the spin Hall effect in an adjacent heavy metal layer are responsible for driving the domain wall motion. It is found that that the sign and magnitude of the domain wall velocity in the uniform flow regime can be tuned significantly by the in-plane magnetic anisotropy. These effects are sensitive to the ratio of the adiabatic and non-adiabatic spin transfer torque parameters and are robust in the presence of pinning and thermal fluctuations.
Energy Technology Data Exchange (ETDEWEB)
Wang, Chih-Hung, E-mail: chwang@phy.ncu.edu.tw [Department of Physics, Tamkang University, Taipei 25137, Taiwan (China); Department of Physics, National Central University, Chungli 320, Taiwan (China); Wu, Yu-Huei, E-mail: yhwu@phy.ncu.edu.tw [Center for Mathematics and Theoretical Physics, National Central University, Chungli 320, Taiwan (China); Department of Physics, National Central University, Chungli 320, Taiwan (China); Hsu, Stephen D.H., E-mail: hsu@uoregon.edu [Institute of Theoretical Science, University of Oregon, Eugene, OR 97403 (United States)
2012-06-18
We study the gravitational effects of a planar domain wall on quantum fluctuations of a massless scalar field during inflation. By obtaining an exact solution of the scalar field equation in de-Sitter space, we show that the gravitational effects of the domain wall break the rotational invariance of the primordial power spectrum without affecting the translational invariance. The strength of rotational violation is determined by one dimensionless parameter {beta}, which is a function of two physical parameters, the domain wall surface tension {sigma} and cosmological constant {Lambda}. In the limit of small {beta}, the leading effect of rotational violation of the primordial power spectrum is scale-invariant.
Multi-scalar tachyon potential on non-BPS domain walls
Brito, F A
2009-01-01
We have considered the multi-scalar and multi-tachyon fields living on a 3d domain wall embedded in a 5d dimensional Minkowski spacetime. The effective action for such a domain wall can be found by integrating out the normal modes as vibrating modes around the domain wall solution of a truncated 5d supergravity action. The multi-scalar tachyon potential are good enough to modeling assisted inflation scenario with multi-tachyon fields. The tachyon condensation are also briefly addressed.
Critical Behavior of Four-Terminal Junctions of Bilayer Graphene Domain Walls
Wieder, Benjamin; Zhang, Fan; Kane, Charles
2014-03-01
Bilayer graphene in a perpendicular electric field can host domain walls between regions of reversed field direction or interlayer stacking. The gapless modes propagating along these domain walls, while not strictly topological, nevertheless have interesting physical properties, including valley-momentum locking. A junction where four domain walls meet forms the analogue of a quantum point contact. We study theoretically the critical behavior of this junction near the pinch-off transition, which is controlled by a non-trivial quantum critical point. At low temperatures, the transition sharpens and the conductance is described by a universal scaling function, which we compute.
N=1 domain wall solutions of massive type II supergravity as generalized geometries
Energy Technology Data Exchange (ETDEWEB)
Louis, J. [Hamburg Univ. (Germany). 2. Inst. fuer Theoretische Physik]|[Hamburg Univ. (Germany). Zentrum fuer Mathematische Physik; Vaula, S. [Hamburg Univ. (Germany). 2. Inst. fuer Theoretische Physik]|[Deutsches Elektronen-Synchrotron (DESY), Hamburg (Germany)
2006-05-15
We study N=1 domain wall solutions of type IIB supergravity compactified on a Calabi-Yau manifold in the presence of RR and NS electric and magnetic fluxes. We show that the dynamics of the scalar fields along the direction transverse to the domain wall is described by gradient flow equations controlled by a superpotential W. We then provide a geometrical interpretation of the gradient flow equations in terms of the mirror symmetric compactification of type IIA. They correspond to a set of generalized Hitchin flow equations of a manifold with SU(3) x SU(3)structure which is fibered over the direction transverse to the domain wall. (Orig.)
Large exchange-dominated domain wall velocities in antiferromagnetically coupled nanowires
Directory of Open Access Journals (Sweden)
Majd Kuteifan
2016-04-01
Full Text Available Magnetic nanowires supporting field- and current-driven domain wall motion are envisioned for methods of information storage and processing. A major obstacle for their practical use is the domain-wall velocity, which is traditionally limited for low fields and currents due to the Walker breakdown occurring when the driving component reaches a critical threshold value. We show through numerical and analytical modeling that the Walker breakdown limit can be extended or completely eliminated in antiferromagnetically coupled magnetic nanowires. These coupled nanowires allow for large domain-wall velocities driven by field and/or current as compared to conventional nanowires.
Domain wall spin structures in mesoscopic Fe rings probed by high resolution SEMPA
Krautscheid, Pascal; Reeve, Robert M.; Lauf, Maike; Krüger, Benjamin; Kläui, Mathias
2016-10-01
We present a combined theoretical and experimental study of the energetic stability and accessibility of different domain wall spin configurations in mesoscopic magnetic iron rings. The evolution is investigated as a function of the width and thickness in a regime of relevance to devices, while Fe is chosen as a material due to its simple growth in combination with attractive magnetic properties including high saturation magnetization and low intrinsic anisotropy. Micromagnetic simulations are performed to predict the lowest energy states of the domain walls, which can be either the transverse or vortex wall spin structure, in good agreement with analytical models, with further simulations revealing the expected low temperature configurations observable on relaxation of the magnetic structure from saturation in an external field. In the latter case, following the domain wall nucleation process, transverse domain walls are found at larger widths and thicknesses than would be expected by just comparing the competing energy terms demonstrating the importance of metastability of the states. The simulations are compared to high spatial resolution experimental images of the magnetization using scanning electron microscopy with polarization analysis to provide a phase diagram of the various spin configurations. In addition to the vortex and simple symmetric transverse domain wall, a significant range of geometries are found to exhibit highly asymmetric transverse domain walls with properties distinct from the symmetric transverse wall. Simulations of the asymmetric walls reveal an evolution of the domain wall tilting angle with ring thickness which can be understood from the thickness dependencies of the contributing energy terms. Analysis of all the data reveals that in addition to the geometry, the influence of materials properties, defects and thermal activation all need to be taken into account in order to understand and reliably control the experimentally accessible
Quantum-induced interactions in the moduli space of degenerate BPS domain walls
Energy Technology Data Exchange (ETDEWEB)
Alonso-Izquierdo, A. [Departamento de Matematica Aplicada and IUFFyM, Universidad de Salamanca,c/ del Parque 2, 37008-Salamanca (Spain); Guilarte, J. Mateos [Departamento de Fisica Fundamental and IUFFyM, Universidad de Salamanca,Plaza de la Merced s/n, 37008-Salamanca (Spain)
2014-01-23
In this paper quantum effects are investigated in a very special two-scalar field model having a moduli space of BPS topological defects. In a (1+1)-dimensional space-time the defects are classically degenerate in mass kinks, but in (3+1) dimensions the kinks become BPS domain walls, all of them sharing the same surface tension at the classical level. The heat kernel/zeta function regularization method will be used to control the divergences induced by the quantum kink and domain wall fluctuations. A generalization of the Gilkey-DeWitt-Avramidi heat kernel expansion will be developed in order to accommodate the infrared divergences due to zero modes in the spectra of the second-order kink and domain wall fluctuation operators, which are respectively N=2×N=2 matrix ordinary or partial differential operators. Use of these tools in the spectral zeta function associated with the Hessian operators paves the way to obtain general formulas for the one-loop kink mass and domain wall tension shifts in any (1+1)- or (3+1)-dimensional N-component scalar field theory model. Application of these formulae to the BPS kinks or domain walls of the N=2 model mentioned above reveals the breaking of the classical mass or surface tension degeneracy at the quantum level. Because the main parameter distinguishing each member in the BPS kink or domain wall moduli space is essentially the distance between the centers of two basic kinks or walls, the breaking of the degeneracy amounts to the surge in quantum-induced forces between the two constituent topological defects. The differences in surface tension induced by one-loop fluctuations of BPS walls give rise mainly to attractive forces between the constituent walls except if the two basic walls are very far apart. Repulsive forces between two close walls only arise if the coupling approaches the critical value from below.
Gomonay, O.; Kläui, M.; Sinova, J.
2016-10-01
Future applications of antiferromagnets (AFs) in many spintronics devices rely on the precise manipulation of domain walls. The conventional approach using static magnetic fields is inefficient due to the low susceptibility of AFs. Recently proposed electrical manipulation with spin-orbit torques is restricted to metals with a specific crystal structure. Here, we propose an alternative, broadly applicable approach: using asymmetric magnetic field pulses to induce controlled ratchet motion of AF domain walls. The efficiency of this approach is based on three peculiarities of AF dynamics. First, a time-dependent magnetic field couples with an AF order parameter stronger than a static magnetic field, which leads to higher mobility of the domain walls. Second, the rate of change of the magnetic field couples with the spatial variation of the AF order parameter inside the domain, and this enables a synchronous motion of multiple domain walls with the same structure. Third, tailored asymmetric field pulses in combination with static friction can prevent backward motion of domain walls and thus lead to the desired controlled ratchet effect. The proposed use of an external field, rather than internal spin-orbit torques, avoids any restrictions on size, conductivity, and crystal structure of the AF material. We believe that our approach paves a way for the development of AF-based devices based on the controlled motion of AF domain walls.
Domain wall motion and Barkhausen effect in magnetic nanoparticles for EOR applications
Baig, Mirza Khurram; Soleimani, Hassan; Yahya, Noorhana
2016-11-01
The domain wall motion in magnetic nanoparticles is a useful parameter of study. The subject of this research is to study of the phenomenon of discontinuous domain wall motion, or the Barkhausen Effect in magnetic nanoparticles. In this work hematite (Fe2O3) nanoparticles have been synthesized using sol-gel auto-combustion and characterized using X-ray diffraction, Field emission scanning electron microscopy (FESEM), Transmission electron microscope (TEM) and Vibrating sample magnetometer (VSM) for crystal structure, morphology, shape, size and magnetic properties respectively. The FESEM and TEM results show that the particles are spherical in nature and average size is 60nm that is suitable for domain walls and barkhuasen effect. The VSM results show high coercivity 175 Oe and low saturation magnetization due to domain wall pinning and barkhausen effect. The size and magnetic properties reveals the existence of domain walls in the synthesized sample. The magnetic properties confirm the energy losses due to domain wall pinning, discontinuous domain rotation or barkhausen effect during magnetization which is useful for oil-water interfacial tension reduction and viscosity of oil. The high surface charge of magnetic nanoparticles and adsorption at the rock surface is useful for wettability alteration of rocks.
Non-Ising and chiral ferroelectric domain walls revealed by nonlinear optical microscopy
Cherifi-Hertel, Salia; Bulou, Hervé; Hertel, Riccardo; Taupier, Grégory; Dorkenoo, Kokou Dodzi (Honorat); Andreas, Christian; Guyonnet, Jill; Gaponenko, Iaroslav; Gallo, Katia; Paruch, Patrycja
2017-06-01
The properties of ferroelectric domain walls can significantly differ from those of their parent material. Elucidating their internal structure is essential for the design of advanced devices exploiting nanoscale ferroicity and such localized functional properties. Here, we probe the internal structure of 180° ferroelectric domain walls in lead zirconate titanate (PZT) thin films and lithium tantalate bulk crystals by means of second-harmonic generation microscopy. In both systems, we detect a pronounced second-harmonic signal at the walls. Local polarimetry analysis of this signal combined with numerical modelling reveals the existence of a planar polarization within the walls, with Néel and Bloch-like configurations in PZT and lithium tantalate, respectively. Moreover, we find domain wall chirality reversal at line defects crossing lithium tantalate crystals. Our results demonstrate a clear deviation from the ideal Ising configuration that is traditionally expected in uniaxial ferroelectrics, corroborating recent theoretical predictions of a more complex, often chiral structure.
Characteristics of domain wall chirality and propagation in a Y-junction nanowire
Energy Technology Data Exchange (ETDEWEB)
Kwak, W.-Y.; Yoon, Seungha; Kwon, J.-H. [School of Materials Science and Engineering, Gwangju Institute of Science and Technology (GIST), Gwangju 61005 (Korea, Republic of); Grünberg, P. [Gruenberg Center for Magnetic Nanomaterials, Gwangju Institute of Science and Technology (GIST), Gwangju 61005 (Korea, Republic of); Cho, B. K., E-mail: chobk@gist.ac.kr [School of Materials Science and Engineering, Gwangju Institute of Science and Technology (GIST), Gwangju 61005 (Korea, Republic of); Gruenberg Center for Magnetic Nanomaterials, Gwangju Institute of Science and Technology (GIST), Gwangju 61005 (Korea, Republic of)
2016-01-14
Chirality-dependent propagation of transverse wall along a nanowire was investigated using a Y-junction with spin-valve structure. It was found that the Y-junction can be used for convenient and effective electric detection of transverse domain wall chirality, especially in a nanowire with sub-200 nm width, where it is difficult to electrically detect chirality using conventional artificial defect, such as a notch, due to small resistance change. Domain wall propagation path in the Y-junction was found to be determined by the wall chirality, whether clockwise or counterclockwise. Using the Y-junction nanowire, characteristics of domain wall chirality that was nucleated in a nucleation pad, attached at the end of a nanowire, were studied and found to be in good agreement with the results of theoretical simulation.
Domain-wall theory and nonstationarity in driven flow with exclusion
Stinchcombe, R. B.; de Queiroz, S. L. A.
2016-07-01
We study the dynamical evolution toward steady state of the stochastic nonequilibrium model known as the totally asymmetric simple exclusion process, in both uniform and nonuniform (staggered) one-dimensional systems with open boundaries. Domain-wall theory and numerical simulations are used and, where pertinent, their results are compared to existing mean-field predictions and exact solutions where available. For uniform chains we find that the inclusion of fluctuations inherent to the domain-wall formulation plays a crucial role in providing good agreement with simulations, which is severely lacking in the corresponding mean-field predictions. For alternating-bond chains the domain-wall predictions for the features of the phase diagram in the parameter space of injection and ejection rates turn out to be realized only in an incipient and quantitatively approximate way. Nevertheless, significant quantitative agreement can be found between several additional domain-wall theory predictions and numerics.
Universal charge and current on magnetic domain walls in Weyl semimetals
Araki, Yasufumi; Yoshida, Akihide; Nomura, Kentaro
2016-09-01
Domain walls in three-dimensional Weyl semimetals, formed by localized magnetic moments, are investigated. There appear bound states around the domain wall with the discrete spectrum, among which we find "Fermi arc" states with the linear dispersion. The Fermi arc modes contribute to the electric charge and current localized at the domain wall, which reveal a universal behavior depending only on chemical potential and the splitting of the Weyl nodes. This equilibrium current can be traced back to the chiral magnetic effect, or the edge counterpart of the anomalous Hall effect in the bulk. We propose a way to manipulate the motion of the domain wall, accompanied with the localized charge, by applying an external electric field.
Sulejmanpasic, Tin; Sandvik, Anders; Unsal, Mithat
2016-01-01
In a spontaneously dimerized quantum antiferromagnet (a valence-bond-solid, VBS) in two or three dimensions, elementary spin-1/2 excitations (spinons) are confined by strings akin to the strings confining quarks in non-abelian gauge theories. The VBS has multiple degenerate ground states (vacua) and domain walls between regions of inequivalent vacua. Here we demonstrate that, if the number of vacua is two, the spinons become liberated (deconfined) on the domain wall. This is in close analogy to supersymmetric gauge theories, where quarks deconfine on domain walls separating two vacua, as first conjecture by Rey and Witten. We show that the confinement mechanism in the VBS and Super-Yang-Mills theory are identical in certain regimes. This remarkable close analogy opens doors to improving our understanding of confinement by computational and experimental studies in quantum magnetism. As an illustration, we present a numerical demonstration of spinon deconfinement on domain walls in a two-dimensional quantum mag...
Beyond the quasi-particle: stochastic domain wall dynamics in soft ferromagnetic nanowires
Hayward, T. J.; Omari, K. A.
2017-03-01
We study the physical origins of stochastic domain wall pinning in soft ferromagnetic nanowires using focused magneto-optic Kerr effect measurements and dynamic micromagnetic simulations. Our results illustrate the ubiquitous nature of these effects in Ni80Fe20 nanowires, and show that they are not only a result of the magnetisation history of the system (i.e. the magnetisation structure of the injected domain walls), and the onset of non-linear propagation dynamics above the Walker breakdown field, but also a complex interplay between the two. We show that this means that, while micromagnetics can be used to make qualitative predictions of the behaviour of domain walls at defect sites, making quantitative predictions is much more challenging. Together, our results reinforce the view that even in these simple pseudo-one dimensional nanomagnets, domain walls must be considered as complex, dynamically evolving objects rather than simple quasi-particles.
Huang, Hao-Ting; Lai, Mei-Feng; Hou, Yun-Fang; Wei, Zung-Hang
2015-05-13
We investigated the influence of magnetic domain walls and magnetic fields on the thermal conductivity of suspended magnetic nanowires. The thermal conductivity of the nanowires was obtained using steady-state Joule heating to measure the change in resistance caused by spontaneous heating. The results showed that the thermal conductivity coefficients of straight and wavy magnetic nanowires decreased with an increase in the magnetic domain wall number, implying that the scattering between magnons and domain walls hindered the heat transport process. In addition, we proved that the magnetic field considerably reduced the thermal conductivity of a magnetic nanowire. The influence of magnetic domain walls and magnetic fields on the thermal conductivity of polycrystalline magnetic nanowires can be attributed to the scattering of long-wavelength spin waves mediated by intergrain exchange coupling.
Multiple integral representation for the trigonometric SOS model with domain wall boundaries
Galleas, W
2011-01-01
Using the dynamical Yang-Baxter algebra we derive a functional equation for the partition function of the trigonometric SOS model with domain wall boundary conditions. The solution of the equation is given in terms of a multiple contour integral.
Analytical modelling and x-ray imaging of oscillations of a single magnetic domain wall
Energy Technology Data Exchange (ETDEWEB)
Bocklage, Lars; Kruger, Benjamin; Fischer, Peter; Meier, Guido
2009-07-10
Domain-wall oscillation in a pinnig potential is described analytically in a one dimensional model for the feld-driven case. For a proper description the pinning potential has to be extended by nonharmonic contributions. Oscillations of a domain wall are observed on its genuine time scale by magnetic X-ray microscopy. It is shown that the nonharmonic terms are present in real samples with a strong restoring potential. In the framework of our model we gain deep insight into the domain-wall motion by looking at different phase spaces. The corrections of the harmonic potential can change the motion of the domain wall significantly. The damping parameter of permalloy is determined via the direct imaging technique.
Li, Songtian; Liu, Xiaoxi; Morisako, Akimistu
2012-09-01
The domain wall movement behaviors under current combining with magnetic field in perpendicularly magnetized TbFeCo wire were studied by a polar magneto-optical Kerr effect microscope. The velocity for domain wall creeping along electrons flowing direction was found to be apparently higher than that of domain wall creeping against electrons flowing, which is the signature of the spin transfer torque effect. By employing the modified field-driven creep motion law, a spin transfer efficiency of 2.7 Oe cm2/10(6) A was determined for TbFeCo wire by treating the spin transfer torque as an effective field adding to the external field. The high spin transfer efficiency suggests that perpendicularly magnetized system with sharp domain walls in TbFeCo film shows high superiorities for applications in spin transfer torque based devices compared with in-plane magnetized systems.
Direct imaging of topological edge states at a bilayer graphene domain wall
Yin, Long-Jing; Jiang, Hua; Qiao, Jia-Bin; He, Lin
2016-06-01
The AB-BA domain wall in gapped graphene bilayers is a rare naked structure hosting topological electronic states. Although it has been extensively studied in theory, a direct imaging of its topological edge states is still missing. Here we image the topological edge states at the graphene bilayer domain wall by using scanning tunnelling microscope. The simultaneously obtained atomic-resolution images of the domain wall provide us unprecedented opportunities to measure the spatially varying edge states within it. The one-dimensional conducting channels are observed to be mainly located around the two edges of the domain wall, which is reproduced quite well by our theoretical calculations. Our experiment further demonstrates that the one-dimensional topological states are quite robust even in the presence of high magnetic fields. The result reported here may raise hopes of graphene-based electronics with ultra-low dissipation.
Fermions with a domain-wall mass: explicit greens function and anomaly cancellation
Chandrasekharan, Shailesh
1994-04-01
We calculate the explicit Greens function for fermions in 2+1 dimensions, with a domain wall mass. We then show a calculation demonstrating the anomaly cancellation when such fermions move in the background of an abelian gauge field.
Stochastic calculation of the QCD Dirac operator spectrum with Mobius domain-wall fermion
Cossu, G; Hashimoto, S; Kaneko, T; Noaki, J
2016-01-01
We calculate the spectral function of the QCD Dirac operator using the four-dimensional effective operator constructed from the Mobius domain-wall implementation. We utilize the eigenvalue filtering technique combined with the stochastic estimate of the mode number. The spectrum in the entire eigenvalue range is obtained with a single set of measurements. Results on 2+1-flavor ensembles with Mobius domain-wall sea quarks at lattice spacing ~ 0.08 fm are shown.
Fine Structure Constant, Domain Walls, and Generalized Uncertainty Principle in the Universe
Directory of Open Access Journals (Sweden)
Luigi Tedesco
2011-01-01
Full Text Available We study the corrections to the fine structure constant from the generalized uncertainty principle in the spacetime of a domain wall. We also calculate the corrections to the standard formula to the energy of the electron in the hydrogen atom to the ground state, in the case of spacetime of a domain wall and generalized uncertainty principle. The results generalize the cases known in literature.
Domain wall solitons and Hopf algebraic translational symmetries in noncommutative field theories
Sasai, Yuya; Sasakura, Naoki
2008-02-01
Domain wall solitons are the simplest topological objects in field theories. The conventional translational symmetry in a field theory is the generator of a one-parameter family of domain wall solutions, and induces a massless moduli field which propagates along a domain wall. We study similar issues in braided noncommutative field theories possessing Hopf algebraic translational symmetries. As a concrete example, we discuss a domain wall soliton in the scalar ϕ4 braided noncommutative field theory in Lie-algebraic noncommutative space-time, [xi,xj]=2iκγijkxk (i,j,k=1,2,3), which has a Hopf algebraic translational symmetry. We first discuss the existence of a domain wall soliton in view of Derrick’s theorem, and construct explicitly a one-parameter family of solutions in perturbation of the noncommutativity parameter κ. We then find the massless moduli field which propagates on the domain wall soliton. We further extend our analysis to the general Hopf algebraic translational symmetry.
Domain wall solitons and Hopf algebraic translational symmetries in noncommutative field theories
Sasai, Yuya
2007-01-01
Domain wall solitons are the simplest topological objects in field theories. The conventional translational symmetry in a field theory is the generator of a one-parameter family of domain wall solutions, and induces a massless moduli field which propagates along a domain wall. We study similar issues in braided noncommutative field theories possessing Hopf algebraic translational symmetries. As a concrete example, we discuss a domain wall soliton in the scalar phi^4 braided noncommutative field theory in Lie-algebraic noncommutative spacetime, [x^i,x^j]=2i kappa epsilon^{ijk}x_k (i,j,k=1,2,3), which has a Hopf algebraic translational symmetry. We first discuss the existence of a domain wall soliton in view of Derrick's theorem, and construct explicitly a one-parameter family of solutions in perturbation of the noncommutativity parameter kappa. We then find the massless moduli field which propagates on the domain wall soliton. We further extend our analysis to the general Hopf algebraic translational symmetry.
Velocity asymmetry of Dzyaloshinskii domain walls in the creep and flow regimes.
Vaňatka, M; Rojas-Sánchez, J-C; Vogel, J; Bonfim, M; Belmeguenai, M; Roussigné, Y; Stashkevich, A; Thiaville, A; Pizzini, S
2015-08-19
We have carried out measurements of domain wall dynamics in a Pt/Co/GdOx(t) wedge sample with perpendicular magnetic anisotropy. When driven by an easy-axis field Hz in the presence of an in-plane field Hx, the domain wall propagation is different along [Formula: see text]x, as expected for samples presenting Dzyaloshinskii-Moriya (DMI) interaction. In the creep regime, the sign and the value of the domain wall velocity asymmetry changes along the wedge. We show that in our samples the domain wall speed versus Hx curves in the creep regime cannot be explained simply in terms of the variation of the domain wall energy with Hx, as suggested by previous works. For this reason the strength and the sign of the DMI cannot be extracted from these measurements. To obtain reliable information on the DMI strength using magnetic field-induced domain wall dynamics, measurements have been performed with high fields, bringing the DW close to the flow regime of propagation. In this case we find large values of the DMI, consistent in magnitude and sign with those obtained from Brillouin light scattering measurements.
Domain wall pinning in FeCoCu bamboo-like nanowires
Berganza, Eider; Bran, Cristina; Jaafar, Miriam; Vázquez, Manuel; Asenjo, Agustina
2016-07-01
The three dimensional nature of cylindrical magnetic nanowires has opened a new way to control the domain configuration as well as the magnetization reversal process. The pinning effect of the periodic diameter modulations on the domain wall propagation in FeCoCu individual nanowires is determined by Magnetic Force Microscopy, MFM. A main bistable magnetic configuration is firstly concluded from MFM images characterized by the spin reversal between two nearly single domain states with opposite axial magnetization. Complementary micromagnetic simulations confirm a vortex mediated magnetization reversal process. A non-standard variable field MFM imaging procedure allows us to observe metastable magnetic states where the propagating domain wall is pinned at certain positions with enlarged diameter. Moreover, it is demonstrated that it is possible to control the position of the pinned domain walls by an external magnetic field.
Quantum transport across van der Waals domain walls in bilayer graphene
Abdullah, H. M.; Van Duppen, B.; Zarenia, M.; Bahlouli, H.; Peeters, F. M.
2017-10-01
Bilayer graphene can exhibit deformations such that the two graphene sheets are locally detached from each other resulting in a structure consisting of domains with different van der Waals inter-layer coupling. Here we investigate how the presence of these domains affects the transport properties of bilayer graphene. We derive analytical expressions for the transmission probability, and the corresponding conductance, across walls separating different inter-layer coupling domains. We find that the transmission can exhibit a valley-dependent layer asymmetry and that the domain walls have a considerable effect on the chiral tunnelling properties of the charge carriers. We show that transport measurements allow one to obtain the strength with which the two layers are coupled. We perform numerical calculations for systems with two domain walls and find that the availability of multiple transport channels in bilayer graphene significantly modifies the conductance dependence on inter-layer potential asymmetry.
Finite-Temperature Atomic Structure of 180^o Ferroelectric Domain Walls in PbTiO3
Angoshtari, Arzhang; Yavari, Arash
2010-01-01
In this letter we obtain the finite-temperature structure of 180^o domain walls in PbTiO3 using a quasi-harmonic lattice dynamics approach. We obtain the temperature dependence of the atomic structure of domain walls from 0K up to room temperature. We also show that both Pb-centered and Ti-centered 180^o domain walls are thicker at room temperature; domain wall thickness at T=300K is about three times larger than that of T=0K. Our calculations show that Ti-centered domain walls have a lower f...
Magnetoresistive logic and biochip
Energy Technology Data Exchange (ETDEWEB)
Brueckl, Hubert E-mail: brueckl@physik.uni-bielefeld.de; Brzeska, Monika; Brinkmann, Dirk; Schotter, J.Joerg; Reiss, Guenter; Schepper, Willi; Kamp, P.-B.; Becker, Anke
2004-11-01
While some magnetoresistive devices based on giant magnetoresistance or spin-dependent tunneling are already commercialized, a new branch of development is evolving towards magnetoresistive logic with magnetic tunnel junctions. Furthermore, the new magnetoelectronic effects show promising properties in magnetoresistive biochips, which are capable of detecting even single molecules (e.g. DNA) by functionalized magnetic markers. The unclear limits of this approach are discussed with two model systems.
Direct observation of domain walls in NiFe films using high-resolution Lorentz microscopy
Wong, Bunsen Y.; Laughlin, David E.
1996-04-01
A novel approach to observe the interaction between magnetic domain wall and nanoscale microstructural features is demonstrated. The method is based on Focault mode Lorentz microscopy and utilizes a Gatan energy image filter to provide additional magnification. A postexperimental image processing technique was applied to separate lattice diffraction from that induced by magnetic domains. The effect of NiFe thickness on the width of a 180° Néel wall has been studied. It was found that the thickness dependence has a similar profile to the theoretically predicted trend but the actual wall thickness is smaller than the calculated values.
Time Variation of the Fine Structure Constant in the Spacetime of a Cosmic Domain Wall
Campanelli, L.; Cea, P.; Tedesco, L.
The gravitational field produced by a domain wall acts as a medium with spacetime-dependent permittivity ɛ. Therefore, the fine structure constant α=e2/4πɛ will be a time-dependent function at fixed position. The most stringent constraint on the time-variation of α comes from the natural reactor Oklo and gives |˙ α /α | < few × 10-17 yr-1. This limit constrains the tension of a cosmic domain wall to be less than σ ≲ 10-2 MeV3, and then represents the most severe limit on the energy density of a cosmic wall stretching our Universe.
Time Variation of the Fine Structure Constant in the Spacetime of a Domain Wall
Campanelli, L; Tedesco, L
2005-01-01
The gravitational field produced by a domain wall acts as a medium with spacetime-dependent permittivity \\epsilon. Therefore, the fine structure constant \\alpha = e^2/4 \\pi \\epsilon will be a time-dependent function at fixed position. The most stringent constraint on the time-variation of \\alpha comes from the natural reactor Oklo and gives |\\dot{\\alpha}/\\alpha| < few 10^{-17} yr^{-1}. This limit constrains the tension of a cosmic domain wall to be less than \\sigma \\lesssim 10^{-2} MeV^3, and then represents the most severe limit on the energy density of a cosmic wall stretching our Universe.
Domain-wall conduction in ferroelectric BiFeO3 controlled by accumulation of charged defects
Rojac, Tadej; Bencan, Andreja; Drazic, Goran; Sakamoto, Naonori; Ursic, Hana; Jancar, Bostjan; Tavcar, Gasper; Makarovic, Maja; Walker, Julian; Malic, Barbara; Damjanovic, Dragan
2016-11-01
Mobile charged defects, accumulated in the domain-wall region to screen polarization charges, have been proposed as the origin of the electrical conductivity at domain walls in ferroelectric materials. Despite theoretical and experimental efforts, this scenario has not been directly confirmed, leaving a gap in the understanding of the intriguing electrical properties of domain walls. Here, we provide atomic-scale chemical and structural analyses showing the accumulation of charged defects at domain walls in BiFeO3. The defects were identified as Fe4+ cations and bismuth vacancies, revealing p-type hopping conduction at domain walls caused by the presence of electron holes associated with Fe4+. In agreement with the p-type behaviour, we further show that the local domain-wall conductivity can be tailored by controlling the atmosphere during high-temperature annealing. This work has possible implications for engineering local conductivity in ferroelectrics and for devices based on domain walls.
Shevchenko, A B; Barabash, M Yu
2015-12-01
It is shown that at low temperatures, quantum oscillations of nanoscale structural inhomogeneities (the vertical Bloch line and the Bloch point) occur in the domain walls of cylindrical magnetic domains formed in a uniaxial magnetic film with strong magnetic anisotropy. The conditions for the excitation of these oscillations are determined.
A Clash-of-Symmetries Mechanism from Intersecting Domain-Wall Branes
Callen, Benjamin D
2013-01-01
We present a new Clash-of-Symmetries mechanism in the context of an intersecting domain-wall brane model in 5+1-dimensional Minkowskian spacetime recently proposed by the authors. This new application of the Dvali-Shifman idea is designed for localizing gauge fields on a domain-wall intersection and we employ it by adding a gauge group $G$ and giving the scalar fields which form lump-like profiles gauge charges. These fields in turn break $G$ to two different subgroups $H_{1}$ and $H_{2}$ on each domain wall, and the gauge fields of these subgroups are taken to be localized to the respective walls by the confinement dynamics of $G$. There is then a further breaking on the domain-wall intersection to $H_{1}\\cap{}H_{2}$ and gauge fields of this overlap group can then be localized to the intersection if they belong inside non-Abelian subgroups of both $H_{1}$ and $H_{2}$ which are spontaneously broken on the intersection and confining in the 4+1D bulks of the respective domain-wall branes. This mechanism has som...
Crossed ratchet effects on magnetic domain walls: geometry and transverse field effects
Energy Technology Data Exchange (ETDEWEB)
Alija, A; Hierro-Rodriguez, A; Perez-Junquera, A; Alameda, J M; Martin, J I; Velez, M, E-mail: mvelez@uniovi.es [Dept. Fisica, Universidad de Oviedo-CINN, 33007 Oviedo (Spain)
2011-08-17
Domain wall propagation across a 2D array of asymmetric holes is strongly dependent on the domain wall configuration: i.e. on whether the wall is flat or kinked. This results in interesting crossed ratchet and asymmetric accommodation effects that have been studied as a function of geometry and transverse field. Micromagnetic simulations have shown that the observation of crossed ratchet effects is easier for arrow than for triangular holes due to a larger field range in which kink propagation is the preferred mode for domain wall motion. Also, it has been found that dc transverse fields can produce a significant enhancement of the easy axis asymmetric accommodation and, also, that ac transverse fields can be rectified by the crossed ratchet potential.
Domain Walls and Textured Vortices in a Two-Component Ginzburg-Landau Model
DEFF Research Database (Denmark)
Madsen, Søren Peder; Gaididei, Yu. B.; Christiansen, Peter Leth
2005-01-01
We look for domain wall and textured vortex solutions in a two-component Ginzburg-Landau model inspired by two-band superconductivity. The two-dimensional two-component model, with equal coherence lengths and no magnetic field, shows some interesting properties. In the absence of a Josephson type...... coupling between the two order parameters a ''textured vortex'' is found by analytical and numerical solution of the Ginzburg-Landau equations. With a Josephson type coupling between the two order parameters we find the system to split up in two domains separated by a domain wall, where the order parameter...
Domain Walls and Textured Vortices in a Two-Component Ginzburg-Landau Model
DEFF Research Database (Denmark)
Madsen, Søren Peder; Gaididei, Yu. B.; Christiansen, Peter Leth
2005-01-01
We look for domain wall and textured vortex solutions in a two-component Ginzburg-Landau model inspired by two-band superconductivity. The two-dimensional two-component model, with equal coherence lengths and no magnetic field, shows some interesting properties. In the absence of a Josephson type...... coupling between the two order parameters a ''textured vortex'' is found by analytical and numerical solution of the Ginzburg-Landau equations. With a Josephson type coupling between the two order parameters we find the system to split up in two domains separated by a domain wall, where the order parameter...
Energy Technology Data Exchange (ETDEWEB)
Schaab, J.; Meier, D., E-mail: dennis.meier@mat.ethz.ch [Department of Materials, ETH Zurich, Vladimir-Prelog-Weg 4, 8093 Zurich (Switzerland); Krug, I. P. [Institut für Optik und Atomare Physik, TU Berlin, Hardenbergstrasse 36, 10623 Berlin (Germany); Forschungszentrum Jülich Peter Grünberg Institute (PGI-6), Leo-Brandt-Strasse, 52425 Jülich (Germany); Nickel, F.; Gottlob, D. M.; Doğanay, H.; Schneider, C. M. [Forschungszentrum Jülich Peter Grünberg Institute (PGI-6), Leo-Brandt-Strasse, 52425 Jülich (Germany); Cano, A. [CNRS, Univ. Bordeaux, ICMCB, UPR 9048, F-33600 Pessac (France); Hentschel, M. [4th Physics Institute and Research Center SCoPE, University of Suttgart, Pfaffenwaldring 57, 70659 Stuttgart (Germany); Materials Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720 (United States); Yan, Z.; Bourret, E. [Materials Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720 (United States); Ramesh, R. [Materials Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720 (United States); Department of Materials Science and Engineering, University of California, Berkeley, California 94720 (United States)
2014-06-09
High-resolution X-ray photoemission electron microscopy (X-PEEM) is a well-established method for imaging ferroelectric domain structures. Here, we expand the scope of application of X-PEEM and demonstrate its capability for imaging and investigating domain walls in ferroelectrics with high spatial resolution. Using ErMnO{sub 3} as test system, we show that ferroelectric domain walls can be visualized based on photo-induced charging effects and local variations in their electronic conductance can be mapped by analyzing the energy distribution of photoelectrons. Our results open the door for non-destructive, contact-free, and element-specific studies of the electronic and chemical structure at domain walls in ferroelectrics.
Domain Walls of D=8 Gauged Supergravities and their D=11 Origin
Alonso-Alberca, N; Gran, U G; Linares, R; Ortín, Tomas; Roest, D
2003-01-01
Performing a Scherk-Schwarz dimensional reduction of D=11 supergravity on a three-dimensional group manifold we construct five D=8 gauged maximal supergravities whose gauge groups are the three-dimensional (non-)compact subgroups of SL(3,R). These cases include the Salam-Sezgin SO(3) gauged supergravity. We construct the most general half-supersymmetric domain wall solutions to these five gauged supergravities. The generic form is a triple domain wall solution whose truncations lead to double and single domain wall solutions. We find that one of the single domain wall solutions has zero potential but nonzero superpotential. Upon uplifting to 11 dimensions each domain wall becomes a purely gravitational 1/2 BPS solution. The corresponding metric has a 7+4 split with a Minkowski 7-metric and a 4-metric that corresponds to a gravitational instanton. These instantons generalize the SO(3) metric of Belinsky, Gibbons, Page and Pope (which includes the Eguchi-Hanson metric) to the other Bianchi types of class A.
Directory of Open Access Journals (Sweden)
Youhei Yamaji
2014-05-01
Full Text Available Topological insulators, in contrast to ordinary semiconductors, accompany protected metallic surfaces described by Dirac-type fermions. Here, we theoretically show that another emergent two-dimensional metal embedded in the bulk insulator is realized at a magnetic domain wall. The domain wall has long been studied as an ingredient of both old-fashioned and leading-edge spintronics. The domain wall here, as an interface of seemingly trivial antiferromagnetic insulators, emergently realizes a functional interface preserved by zero modes with robust two-dimensional Fermi surfaces, where pyrochlore iridium oxides proposed to host the condensed-matter realization of Weyl fermions offer such examples at low temperatures. The existence of in-gap states that are pinned at domain walls, theoretically resembling spin or charge solitons in polyacetylene, and protected as the edges of hidden one-dimensional weak Chern insulators characterized by a zero-dimensional class-A topological invariant, solves experimental puzzles observed in R_{2}Ir_{2}O_{7} with rare-earth elements R. The domain wall realizes a novel quantum confinement of electrons and embosses a net uniform magnetization that enables magnetic control of electronic interface transports beyond the semiconductor paradigm.
Direct observation of interlocked domain walls in hexagonal RMnO3 (R=Tm, Lu)
Zhang, Q. H.; Wang, L. J.; Wei, X. K.; Yu, R. C.; Gu, L.; Hirata, A.; Chen, M. W.; Jin, C. Q.; Yao, Y.; Wang, Y. G.; Duan, X. F.
2012-01-01
Using state-of-the-art aberration-corrected annular-bright-field and high-angle annular-dark-field scanning transmission electron microscopy, we investigated domain wall structures in multiferroic hexagonal TmMnO3 and LuMnO3 ceramics at the atomic scale. Two types of 180° domain walls (DWs), i.e., the transverse and the longitudinal DWs with uniform displacements of a/3 and 2a/3, respectively, were identified along the b direction, which is in agreement with the interlock between the ferroelectric and structural translation domain walls that had been predicted previously. Across the domain wall the arrangement of MnO5 polyhedra was not found to be inversed, indicating that (i) it has negligible effects on the polarization and (ii) the structures of the neighbor domains with opposite polarizations are not exactly the same. These wall structures are different from the polarization inversion in conventional ferroelectrics and may be used to explain the unusual transport properties and magnetoelectic effects.
The defects influence on domain wall propagation in bistable glass-coated microwires
Energy Technology Data Exchange (ETDEWEB)
Rodionova, V. [Magnetism Division, Faculty of Physics, M.V. Lomonosov Moscow State University, Moscow 119991 (Russian Federation); Immanuel Kant Baltic Federal University, Kaliningrad 236041 (Russian Federation); Dpto. Fisica de Materiales, Fac. Quimicas, UPV/EHU, San Sebastian 20018 (Spain); Zhukova, V., E-mail: valentina.zhukova@ehu.es [Dpto. Fisica de Materiales, Fac. Quimicas, UPV/EHU, San Sebastian 20018 (Spain); Ilyn, M.; Ipatov, M. [Dpto. Fisica de Materiales, Fac. Quimicas, UPV/EHU, San Sebastian 20018 (Spain); Perov, N. [Magnetism Division, Faculty of Physics, M.V. Lomonosov Moscow State University, Moscow 119991 (Russian Federation); Zhukov, A. [Dpto. Fisica de Materiales, Fac. Quimicas, UPV/EHU, San Sebastian 20018 (Spain); IKERBASQUE, Basque Foundation for Science, Bilbao 48011 (Spain)
2012-05-01
We studied the domain wall (DW) dynamics of magnetically bistable amorphous glass-coated Fe{sub 74}B{sub 13}Si{sub 11}C{sub 2} microwires. In according to our experimental results magnetic field dependences of DW velocity of studied microwires can be divided into two groups: with uniform or uniformly accelerated DW propagation along the microwire. Strong correlation between the type of the magnetic field dependence of domain wall velocity, v(H), and the distribution of the local nucleation fields has been observed. Moreover, we observed abrupt increasing of DW velocity (jump) on the magnetic field dependences of the domain wall velocity, v(H), for the both types of the v(H) dependences. At the same time usual linear increasing of the domain wall velocity with magnetic field persists below these jumps. It was found that the jump height correlates with the location of nucleation place of the new domain wall. We have measured local nucleation field distribution in all the microwires. From local nucleation field distribution we have obtained the DW nucleation locations and estimated the jump height.
Spin distributions and dynamics in domain walls guided by soft magnetic nanowire structures
Yang, Jusang; Erskine, James L.
2017-01-01
Numerical simulations are used to investigate static and dynamic properties of spin distributions within domain walls confined by rectangular cross section Permalloy nanowire conduits having widths up to 1000 nm and thickness up to 50 nm. Phase boundaries and critical regions associated with domain-wall spin distributions of various topologies [transverse (or asymmetric transverse), vortex, double-vortex, triple-vortex and cross-tie] are accurately determined using high-performance computing resources. Mobility curves are calculated that characterize domain-wall propagation for an interesting region of the spin texture phase diagram: 20 nm thick nanowires with widths of 60-700 nm at axial drive fields extending to 150 Oe. The simulations (and corresponding experiments, which are discussed), reveal new propagating fixed configuration domain-wall topologies with enhanced velocity. Effects of temperature on the spin distributions and dynamics are explored, by conducting simulations that include separately varying temperature-dependent parameters (saturation magnetization and exchange constant) and simulating effects of temperature-dependent fluctuations using the Langevin dynamics feature of the simulation code. Related temperature-dependent experiments are discussed. The simulation studies demonstrate a close connection between static and (field-driven) dynamic spin configurations in nanowire-confined domain walls and demonstrate the importance of exploring model-system parameter space at high numerical precision.
Detection of ferromagnetic domain wall pinning and depinning with a semiconductor device
Energy Technology Data Exchange (ETDEWEB)
Malec, Chris E.; Bennett, Brian R.; Johnson, Mark B. [Naval Research Laboratory, Washington, D.C. 20375 (United States)
2015-12-21
We demonstrate the detection of a ferromagnetic domain wall using a nanoscale Hall cross. A narrow permalloy wire is defined lithographically on top of a Hall cross fabricated from an InAs quantum well. The width of the Hall cross (500 nm–1 μm) is similar to the width of the ferromagnetic wire (200–500 nm), and a geometric pinning site is fabricated in the ferromagnetic wire to trap a domain wall within the area of the Hall cross. The devices provide a signal that is often the same order of magnitude as the offset Hall voltage when a domain wall is located above the Hall cross, and may be useful for memory applications. Different geometries for the Hall cross and ferromagnetic wire are tested, and radiofrequency pulses are sent into the wire to demonstrate current driven domain wall motion. Further changes to the Hall bar geometry with respect to the wire geometry are investigated by numerical computation. A large gain in signal is seen for Hall bars only slightly wider than the ferromagnetic wires as compared to those twice as wide, as well as a larger sensitivity to the exact position of the domain wall with respect to the center of the Hall cross.
Vacuum Domain Walls in D-dimensions Local and Global Space-Time Structure
Cvetic, M; Cvetic, Mirjam; Wang, Jing
2000-01-01
We study local and global gravitational effects of (D-2)-brane configurations (domain-walls) in the vacuum of D-dimensional space-time. We focus on infinitely thin vacuum domain walls with arbitrary cosmological constants on either side of the wall. In the comoving frame of the wall we derive a general metric Ansatz, consistent with the homogeneity and isotropy of the space-time intrinsic to the wall, and employ Israel's matching conditions at the wall. The space-time, intrinsic to the wall, is that of (D-1)-dimensional Freedman-Lemaitre-Robertson-Walker universe (with k=-1,0,1) which has a (local) description as either anti-deSitter, Minkowski or deSitter space-time. For each of these geometries, we provide a systematic classification of the local and global space-time structure transverse to the walls, for those with both positive and negative tension; they fall into different classes according to the values of their energy density relative to that of the extreme (superysmmetric) configurations. We find tha...
Energy-efficient writing scheme for magnetic domain-wall motion memory
Kim, Kab-Jin; Yoshimura, Yoko; Ham, Woo Seung; Ernst, Rick; Hirata, Yuushou; Li, Tian; Kim, Sanghoon; Moriyama, Takahiro; Nakatani, Yoshinobu; Ono, Teruo
2017-04-01
We present an energy-efficient magnetic domain-writing scheme for domain wall (DW) motion-based memory devices. A cross-shaped nanowire is employed to inject a domain into the nanowire through current-induced DW propagation. The energy required for injecting the magnetic domain is more than one order of magnitude lower than that for the conventional field-based writing scheme. The proposed scheme is beneficial for device miniaturization because the threshold current for DW propagation scales with the device size, which cannot be achieved in the conventional field-based technique.
A micromagnetic study of the oscillations of pinned domain walls in magnetic ribbons
Energy Technology Data Exchange (ETDEWEB)
Alejos, Oscar [Dpto. Electricidad y Electronica, Universidad de Valladolid, 47071 Valladolid (Spain)]. E-mail: oscaral@ee.uva.es; Torres, Carlos [Dpto. Electricidad y Electronica, Universidad de Valladolid, 47071 Valladolid (Spain); Hernandez-Gomez, Pablo [Dpto. Electricidad y Electronica, Universidad de Valladolid, 47071 Valladolid (Spain); Lopez-Diaz, Luis [Dpto. Fisica Aplicada, Universidad de Salamanca, 37071 Salamanca (Spain); Torres, Luis [Dpto. Fisica Aplicada, Universidad de Salamanca, 37071 Salamanca (Spain); Martinez, Eduardo [Dpto. Ingenieria Electromecanica, Universidad de Burgos, 09001 Burgos (Spain)
2007-09-15
The work studies the dynamics of domain walls in magnetic ribbons with thicknesses of the order of magnitude of the permalloy exchange length (5.7 nm) by means of micromagnetic simulations. Two small defects are symmetrically placed on both edges of the ribbon, one on each edge, occupying the whole ribbon thickness. One transverse domain wall is pinned by the defects, in a head-to-head configuration. A free wall oscillation is forced by applying a static external magnetic field in the direction of the large axis until the wall reaches a new equilibrium position (elongation), and then removed. Three dynamic regimes are observed depending on the size of the cross ribbon section.
Unstable equilibrium point in chaotic domain-wall motion and Ott-Grebogi-Yorke control
Okuno, H.; Takemura, Y.
2001-06-01
A method for finding the unstable equilibrium points in Bloch wall motion is proposed, which is important for controlling the chaotic domain-wall motion by using the Ott-Grebogi-Yorke (OGY) method. The dynamics of Bloch wall motion are expressed by a nonlinear differential equation with the terms of inertia, damping, restoring, and an external magnetic drive force. An equation is transformed into the difference equations by following the OGY method, approximating linearly around an unstable equilibrium point (a saddle point), and adding a controlling input. The unstable equilibrium points are obtained by using the return map and the condition of hyperbolic fixed point. The time series of domain-wall motion successfully controlled on the unstable equilibrium points by the OGY method is shown.
Valence-bond-solid domain walls in a 2D quantum magnet
Shao, Hui; Guo, Wenan; Sandvik, Anders
sing quantum Monte Carlo simulations, we study properties of domain walls in a square-lattice S=1/2 Heisenberg model with additional interactions which can drive the system from an antiferromagnetic (AFM) ground state to a valence-bond solid (VBS). We study the finite-size scaling of the domain-wall energy at the putative ''deconfined'' critical AFM-VBS point, which gives access to the critical exponent governing the domain-wall width. This length-scale diverges faster than the correlation length and also is related to the scale of spinon deconfinement. Our results show additional evidence of deconfied quantum criticality and are compatible with critical exponents extracted from finite-size scaling of other quantities. NSFC Grant No. 11175018, NSF Grant No. DMR-1410126.
Domain Wall Motion in Magnetic Nanostrips under the Influence of Rashba Field
Directory of Open Access Journals (Sweden)
Vito Puliafito
2012-01-01
Full Text Available Spin-orbit Rashba effect applies a torque on the magnetization of a ferromagnetic nanostrip in the case of structural inversion asymmetry, also affecting the steady domain wall motion induced by a spin-polarized current. This influence is here analytically studied in the framework of the extended Landau-Lifshitz-Gilbert equation, including the Rashba effect as an additive term of the effective field. Results of previous micromagnetic simulations and experiments have shown that this field yields an increased value of the Walker breakdown current together with an enlargement of the domain wall width. In order to analytically describe these results, the standard travelling wave ansatz for the steady domain wall motion is here adopted. Results of our investigations reveal the impossibility to reproduce, at the same time, the previous features and suggest the need of a more sophisticated model whose development requires, in turn, additional information to be extracted from ad hoc micromagnetic simulations.
Influence of exchange coupling on current-driven domain wall motion in a nanowire
Energy Technology Data Exchange (ETDEWEB)
Komine, Takashi, E-mail: komine@mx.ibaraki.ac.j [Department of Media and Telecommunications Engineering, Ibaraki University, Ibaraki 316-8511 (Japan); Takahashi, Kota; Murakami, Hiroshi; Sugita, Ryuji [Department of Media and Telecommunications Engineering, Ibaraki University, Ibaraki 316-8511 (Japan)
2010-10-15
In this study, the effect of exchange stiffness constant on current-driven domain wall motion in nanowires with in-plane magnetic anisotropy (IMA) and perpendicular magnetic anisotropy (PMA) has been investigated using micromagnetic simulation. The critical current density in a nanowire with IMA decreases as the exchange stiffness constant decreases because the domain wall width at the upper edge of the nanowire narrows according to the decrease of the exchange stiffness constant. On the other hand, the critical current density in a nanowire with PMA slightly decreases contrary to that of IMA although the domain wall width reasonably decreases as the exchange stiffness constant decreases. The slight reduction rate of the critical current density is due to the increase of the effective hard-axis anisotropy of PMA nanowire.
Chiral Symmetry Breaking for Domain Wall Fermions in Quenched Lattice QCD
Wu, L
2001-01-01
The domain wall fermion formulation exhibits full chiral symmetry for finite lattice spacing except for the effects of mixing between the domain walls. Close to the continuum limit these symmetry breaking effects should be described by a single residual mass. We determine this mass from the conservation law obeyed by the conserved axial current in quenched simulations with beta=5.7 and 6.0 and domain wall separations varying between 12 and 48 on 8^3x32 and 16^3x32 lattices. Using the resulting values for the residual mass we perform two complete and independent calculations of the pion decay constant. Good agreement is found between these two methods and with experiment.
Critical behavior of four-terminal conductance of bilayer graphene domain walls
Wieder, Benjamin J.; Zhang, Fan; Kane, C. L.
2015-08-01
Bilayer graphene in a perpendicular electric field can host domain walls between regions of reversed field direction or interlayer stacking. The gapless modes propagating along these domain walls, while not strictly topological, nevertheless have interesting physical properties, including valley-momentum locking. A junction where two domain walls intersect forms the analog of a quantum point contact. We study theoretically the critical behavior of this junction near the pinch-off transition, which is controlled by two separate classes of nontrivial quantum critical points. For strong interactions, the junction can host phases of unique charge and valley conductances. For weaker interactions, the low-temperature charge conductance can undergo one of two possible quantum phase transitions, each characterized by a specific critical exponent and a collapse to a universal scaling function, which we compute.
Energy Technology Data Exchange (ETDEWEB)
Sánchez-Tejerina, L. [Dpto. Electricidad y Electrónica, Facultad de Ciencias, Universidad de Valladolid, 47011 Valladolid (Spain); Alejos, Ó., E-mail: oscaral@ee.uva.es [Dpto. Electricidad y Electrónica, Facultad de Ciencias, Universidad de Valladolid, 47011 Valladolid (Spain); Martínez, E. [Dpto. Física Aplicada, Facultad de Ciencias, Universidad de Salamanca, 37011 Salamanca (Spain); Muñoz, J.M. [Dpto. Electricidad y Electrónica, Facultad de Ciencias, Universidad de Valladolid, 47011 Valladolid (Spain)
2016-07-01
The dynamics of domain walls in ultrathin ferromagnetic strips with perpendicular magnetic anisotropy is studied from both numerical and analytical micromagnetics. The influence of a moderate interfacial Dzyaloshinskii–Moriya interaction associated to a bi-layer strip arrangement has been considered, giving rise to the formation of Dzyaloshinskii domain walls. Such walls possess under equilibrium conditions an inner magnetization structure defined by a certain orientation angle that make them to be considered as intermediate configurations between Bloch and Néel walls. Two different dynamics are considered, a field-driven and a current-driven dynamics, in particular, the one promoted by the spin torque due to the spin-Hall effect. Results show an inherent asymmetry associated with the rotation of the domain wall magnetization orientation before reaching the stationary regime, characterized by a constant terminal speed. For a certain initial DW magnetization orientation at rest, the rotation determines whether the reorientation of the DW magnetization prior to reach stationary motion is smooth or abrupt. This asymmetry affects the DW motion, which can even reverse for a short period of time. Additionally, it is found that the terminal speed in the case of the current-driven dynamics may depend on either the initial DW magnetization orientation at rest or the sign of the longitudinally injected current. - Highlights: • The asymmetric response of domain walls in bilayer strips with PMA is studied. • Out-of-plane fields and SHE longitudinal currents are applied. • The response is associated to the rotation of the domain wall inner magnetization. • Clockwise and counter-clockwise magnetization rotations are not equivalent. • The asymmetry results in different travelled distances and/or terminal speeds.
Energy Technology Data Exchange (ETDEWEB)
Toscano, D., E-mail: danilotoscano@fisica.ufjf.br [Departamento de Física, Laboratório de Simulação Computacional, Universidade Federal de Juiz de Fora, Juiz de Fora, Minas Gerais 36036–330 (Brazil); Leonel, S.A., E-mail: sidiney@fisica.ufjf.br [Departamento de Física, Laboratório de Simulação Computacional, Universidade Federal de Juiz de Fora, Juiz de Fora, Minas Gerais 36036–330 (Brazil); Coura, P.Z., E-mail: pablo@fisica.ufjf.br [Departamento de Física, Laboratório de Simulação Computacional, Universidade Federal de Juiz de Fora, Juiz de Fora, Minas Gerais 36036–330 (Brazil); Sato, F., E-mail: sjfsato@fisica.ufjf.br [Departamento de Física, Laboratório de Simulação Computacional, Universidade Federal de Juiz de Fora, Juiz de Fora, Minas Gerais 36036–330 (Brazil); Costa, B.V., E-mail: bvc@fisica.ufmg.br [Departamento de Física, Laboratório de Simulação, Universidade Federal de Minas Gerais, Belo Horizonte, Minas Gerais 30123–970 (Brazil); Vázquez, M., E-mail: mvazquez@icmm.csic.es [Instituto de Ciencia de Materiales de Madrid, CSIC. 28049 Madrid (Spain)
2016-12-01
Numerical simulations have been used to investigate the polarity reversal of the transverse domain wall in rectangular magnetic nanowires and the stabilization of the domain wall position after occurring the polarity reversal. In order to control the wall position we have considered two clusters of magnetic impurities, identical and equidistant from the nanowire width axis. Traps of pinning and blocking for the transverse domain wall can be originated from magnetic impurities, consisting of a local variation of the exchange constant. Under suitable excitation amplitudes it is possible to switch the polarity of the transverse domain wall by applying a nanosecond axial magnetic field pulse in a fast and controllable way. - Highlights: • Traps for pinning and blocking transverse domain walls are proposed. • The traps consisting of localized modifications of the magnetic properties. • The wall polarity can be reversed in a fast and controllable way.
Directory of Open Access Journals (Sweden)
Zhaoliang Liao
2014-09-01
Full Text Available La2/3Sr1/3MnO3 films with uniaxial magnetic anisotropy were coherently grown on NdGaO3 (110 substrates. The uniaxial anisotropy has strong effect on magnetoresistance (MR. A positive MR was observed when the current is along magnetic easy axis under the current-field perpendicular geometry. In contrast, no positive MR is observed when current is along the magnetic hard axis regardless of the field direction. Our analysis indicates that the anomalous anisotropic MR effect arises from the uniaxial magnetic anisotropy caused stripe domains which contribute to strong anisotropic domain wall resistivity.
Directory of Open Access Journals (Sweden)
S. Dutta
2015-12-01
Full Text Available Reducing the switching energy of devices that rely on magnetic domain wall motion requires scaling the devices to widths well below 100 nm, where the nanowire line edge roughness (LER is an inherent source of domain wall pinning. We investigate the effects of periodic and isolated rectangular notches, triangular notches, changes in anisotropy, and roughness measured from images of fabricated wires, in sub-100-nm-wide nanowires with in-plane and perpendicular magnetic anisotropy using micromagnetic modeling. Pinning fields calculated for a model based on discretized images of physical wires are compared to experimental measurements. When the width of the domain wall is smaller than the notch period, the domain wall velocity is modulated as the domain wall propagates along the wire. We find that in sub-30-nm-wide wires, edge defects determine the operating threshold and domain wall dynamics.
Richter, Kornel; Krone, Andrea; Mawass, Mohamad-Assaad; Krüger, Benjamin; Weigand, Markus; Stoll, Hermann; Schütz, Gisela; Kläui, Mathias
2016-07-01
We report time-resolved observations of field-induced domain wall nucleation in asymmetric ferromagnetic rings using single direction field pulses and rotating fields. We show that the asymmetric geometry of a ring allows for controlling the position of nucleation events, when a domain wall is nucleated by a rotating magnetic field. Direct observation by scanning transmission x-ray microscopy (STXM) reveals that the nucleation of domain walls occurs through the creation of transient ripplelike structures. This magnetization state is found to exhibit a surprisingly high reproducibility even at room temperature and we determine the combinations of field strengths and field directions that allow for reliable nucleation of domain walls and directly quantify the stability of the magnetic states. Our analysis of the processes occurring during field induced domain wall nucleation shows how the effective fields determine the nucleation location reproducibly, which is a key prerequisite toward using domain walls for spintronic devices.
Domain Walls and Flux Tubes in N=2 SQCD D-Brane Prototypes
Shifman, M
2003-01-01
This paper could have been entitled "D branes and strings from flesh and blood." We study field theoretic prototypes of D branes/strings. To this end we consider (2+1)-dimensional domain walls in (3+1)-dimensional N=2 SQCD with SU(2) gauge group and two quark flavors in the fundamental representation. This theory is perturbed by a small mass term of the adjoint matter which, in the leading order in the mass parameter, does not break N=2 supersymmetry, and reduces to a (generalized) Fayet-Iliopoulos term in the effective low-energy N=2 SQED. We find 1/2 BPS-saturated domain wall solution interpolating between two quark vacua at weak coupling, and show that this domain wall localizes a U(1) gauge field. To make contact with the brane/string picture we consider the Abrikosov-Nielsen-Olesen magnetic flux tube in one of two quark vacua and demonstrate that it can end on the domain wall. We find an explicit 1/4 BPS-saturated solution for the wall/flux tube junction. We verify that the end point of the flux tube on ...
Gravitational waves from domain walls in the next-to-minimal supersymmetric standard model
Energy Technology Data Exchange (ETDEWEB)
Kadota, Kenji [Center for Theoretical Physics of the Universe, Institute for Basic Science,Daejeon 305-811 (Korea, Republic of); Kawasaki, Masahiro [Institute for Cosmic Ray Research, The University of Tokyo,5-1-5 Kashiwa-no-ha, Kashiwa City, Chiba 277-8582 (Japan); Kavli Institute for the Physics and Mathematics of the Universe (WPI),Todai Institutes for Advanced Study, The University of Tokyo,5-1-5 Kashiwa-no-ha, Kashiwa City, Chiba 277-8582 (Japan); Saikawa, Ken’ichi [Department of Physics, Tokyo Institute of Technology,2-12-1 Ookayama, Meguro-ku, Tokyo 152-8551 (Japan)
2015-10-16
The next-to-minimal supersymmetric standard model predicts the formation of domain walls due to the spontaneous breaking of the discrete Z{sub 3}-symmetry at the electroweak phase transition, and they collapse before the epoch of big bang nucleosynthesis if there exists a small bias term in the potential which explicitly breaks the discrete symmetry. Signatures of gravitational waves produced from these unstable domain walls are estimated and their parameter dependence is investigated. It is shown that the amplitude of gravitational waves becomes generically large in the decoupling limit, and that their frequency is low enough to be probed in future pulsar timing observations.
Ding, Song; Tian, GuiYun; Dobmann, Gerd; Wang, Ping
2017-01-01
Skewness of Magnetic Barkhausen Noise (MBN) signal is used as a new feature for applied stress determination. After experimental studies, skewness presents its ability for measuring applied tensile stress compared with conventional feature, meanwhile, a non-linear behavior of this new feature and an independence of the excitation conditions under compressive stress are found and discussed. Effective damping during domain wall motion influencing the asymmetric shape of the MBN statistical distribution function is discussed under compressive and tensile stress variation. Domain wall (DW) energy and distance between pinning edges of the DW are considered altering the characteristic relaxation time, which is the reason for the non-linear phenomenon of skewness.
Domain Walls in Non-Equilibrium Systems and the Emergence of Persistent Patterns
Hagberg, A
1993-01-01
Abstract: Domain walls in equilibrium phase transitions propagate in a preferred direction so as to minimize the free energy of the system. As a result, initial spatio-temporal patterns ultimately decay toward uniform states. The absence of a variational principle far from equilibrium allows the coexistence of domain walls propagating in any direction. As a consequence, *persistent* patterns may emerge. We study this mechanism of pattern formation using a non-variational extension of Landau's model for second order phase transitions. PACS numbers: 05.70.Fh, 42.65.Pc, 47.20.Ky, 82.20Mj
Effect of Joule heating in current-driven domain wall motion
A., Yamaguchi; S., Nasu; H., Tanigawa; T., Ono; K., Miyake; Ko, Mibu; T., Shinjo
2004-01-01
It was found that high current density needed for the current-driven domain wall motion results in the Joule heating of the sample. The sample temperature, when the current-driven domain wall motion occurred, was estimated by measuring the sample resistance during the application of a pulsed current. The sample temperature was 750 K for the threshold current density of 6.7×1011 A/m2 in a 10-nm-thick Ni81Fe19 wire with a width of 240 nm on thermally oxidized silicon substrate. The temperature ...
Effect of Joule heating in current-driven domain wall motion
Yamaguchi, A.; Tanigawa, H.; Ono, T.; Nasu, S; Miyake, K.; Mibu, K.; Shinjo, T.
2004-01-01
It was found that high current density needed for the current-driven domain wall motion results in the Joule heating of the sample. The sample temperature, when the current-driven domain wall motion occurred, was estimated by measuring the sample resistance during the application of a pulsed-current. The sample temperature was 750 K for the threshold current density of 6.7 x 10^11 A/m2 in a 10 nm-thick Ni81Fe19 wire with a width of 240 nm. The temperature was raised to 830 K for the current d...
Simulations of super-structure domain walls in two dimensional assemblies of magnetic nanoparticles
DEFF Research Database (Denmark)
Jordanovic, Jelena; Beleggia, Marco; Schiøtz, Jakob
2015-01-01
taking the role of the atomic spins. The coupling is, however, different. The superspins interact only by dipolar interactions as exchange coupling between individual nanoparticles may be neglected due to interparticle spacing. We observe that it is energetically favorable to introduce domain walls...... oriented along the long dimension of nanoparticle assemblies rather than along the short dimension. This is unlike what is typically observed in continuous magnetic materials, where the exchange interaction introduces an energetic cost proportional to the area of the domain walls. Structural disorder...
Tachyon condensation due to domain-wall annihilation in Bose-Einstein condensates.
Takeuchi, Hiromitsu; Kasamatsu, Kenichi; Tsubota, Makoto; Nitta, Muneto
2012-12-14
We show theoretically that a domain-wall annihilation in two-component Bose-Einstein condensates causes tachyon condensation accompanied by spontaneous symmetry breaking in a two-dimensional subspace. Three-dimensional vortex formation from domain-wall annihilations is considered a kink formation in subspace. Numerical experiments reveal that the subspatial dynamics obey the dynamic scaling law of phase-ordering kinetics. This model is experimentally feasible and provides insights into how the extra dimensions influence subspatial phase transition in higher-dimensional space.
Manipulation of a Nuclear Spin by a Magnetic Domain Wall in a Quantum Hall Ferromagnet
Korkusinski, M.; Hawrylak, P.; Liu, H. W.; Hirayama, Y.
2017-03-01
The manipulation of a nuclear spin by an electron spin requires the energy to flip the electron spin to be vanishingly small. This can be realized in a many electron system with degenerate ground states of opposite spin polarization in different Landau levels. We present here a microscopic theory of a domain wall between spin unpolarized and spin polarized quantum Hall ferromagnet states at filling factor two with the Zeeman energy comparable to the cyclotron energy. We determine the energies and many-body wave functions of the electronic quantum Hall droplet with up to N = 80 electrons as a function of the total spin, angular momentum, cyclotron and Zeeman energies from the spin singlet ν = 2 phase, through an intermediate polarization state exhibiting a domain wall to the fully spin-polarized phase involving the lowest and the second Landau levels. We demonstrate that the energy needed to flip one electron spin in a domain wall becomes comparable to the energy needed to flip the nuclear spin. The orthogonality of orbital electronic states is overcome by the many-electron character of the domain - the movement of the domain wall relative to the position of the nuclear spin enables the manipulation of the nuclear spin by electrical means.
New confining force solution of the QCD axion domain-wall problem.
Barr, S M; Kim, Jihn E
2014-12-12
The serious cosmological problems created by the axion-string-axion-domain-wall system in standard axion models are alleviated by positing the existence of a new confining force. The instantons of this force can generate an axion potential that erases the axion strings long before QCD effects become important, thus preventing QCD-generated axion walls from ever appearing. Axion walls generated by the new confining force would decay so early as not to contribute significantly to the energy in axion dark matter.
Stability of gravity-scalar systems for domain-wall models with a soft wall
George, Damien P
2010-01-01
We show that it is possible to create an RS soft-wall model, a model with a compact extra dimension, without using fundamental branes. All that is required are bulk scalar fields minimally coupled to gravity. Of crucial importance is the stability of the size of the extra dimension. Without branes, one cannot easily implement the Goldberger-Wise mechanism, and instead it must be shown that the scalar configuration is stable in its own right. We use the superpotential approach for generating solutions, the so called 'fake supergravity' scenario, and show that configurations generated in such a way are always free of tachyonic modes. Furthermore, we show that the model is also free of zero modes (in the spin-0 sector) if all the scalars have odd parity. We discuss the hierarchy problem in soft-wall models, and applications of our analysis to the AdS/QCD correspondence.
Miyamoto, S; Miura, T; Watanabe, S; Nagase, K; Hirayama, Y
2016-03-09
We present fractional quantum Hall domain walls confined in a gate-defined wire structure. Our experiments utilize spatial oscillation of domain walls driven by radio frequency electric fields to cause nuclear magnetic resonance. The resulting spectra are discussed in terms of both large quadrupole fields created around the wire and hyperfine fields associated with the oscillating domain walls. This provides the experimental fact that the domain walls survive near the confined geometry despite of potential deformation, by which a localized magnetic resonance is allowed in electrical means.
Sánchez-Tejerina, L.; Alejos, Ó.; Martínez, E.; Muñoz, J. M.
2016-07-01
The dynamics of domain walls in ultrathin ferromagnetic strips with perpendicular magnetic anisotropy is studied from both numerical and analytical micromagnetics. The influence of a moderate interfacial Dzyaloshinskii-Moriya interaction associated to a bi-layer strip arrangement has been considered, giving rise to the formation of Dzyaloshinskii domain walls. Such walls possess under equilibrium conditions an inner magnetization structure defined by a certain orientation angle that make them to be considered as intermediate configurations between Bloch and Néel walls. Two different dynamics are considered, a field-driven and a current-driven dynamics, in particular, the one promoted by the spin torque due to the spin-Hall effect. Results show an inherent asymmetry associated with the rotation of the domain wall magnetization orientation before reaching the stationary regime, characterized by a constant terminal speed. For a certain initial DW magnetization orientation at rest, the rotation determines whether the reorientation of the DW magnetization prior to reach stationary motion is smooth or abrupt. This asymmetry affects the DW motion, which can even reverse for a short period of time. Additionally, it is found that the terminal speed in the case of the current-driven dynamics may depend on either the initial DW magnetization orientation at rest or the sign of the longitudinally injected current.
Domain wall signatures in BICEP2, Planck, VLT/UVES and Keck/HIRES data?
Avelino, P P
2014-01-01
We consider the possibility that current hints for a spatial variation of the fine structure constant at high redshift could be due to a domain wall network described by a scalar field non-minimally coupled to the electromagnetic field. We show that in order to be cause of the reported spatial variation of the fine structure constant, without being in conflict with the observed anisotropies of the cosmic microwave background, the characteristic scale of the network would have to be of the order of the Hubble radius and the fractional contribution of the domain wall network to the energy density of the Universe would need to be in the range $10^{-10} < \\Omega_{w0} < 10^{-5}$. We argue that for sufficiently large values of $\\Omega_{w0}$ in this range, domain walls could even be responsible for the large scale anomalies in the temperature distribution of the cosmic microwave background detected by Planck and WMAP and for the B-mode polarisation signature detected by BICEP2. Since the domain wall contributi...
Quark matter coupled to domain walls in Bianchi types II, VIII and IX Universes
Indian Academy of Sciences (India)
S D Katore; M M Sancheti; S P Hatkar
2014-10-01
In this study of Bianchi types II, VIII and IX Universes, quark matter coupled to domain walls in the context of general relativity are explored. To obtain deterministic solution of the Einstein’s field equations, various techniques are adopted. The features of the obtained solution are discussed.
Model of hybrid interfacial domain wall in ferromagnetic/antiferromagnetic bilayers
Zhang, Wen; Zhai, Ya; Lu, Mu; You, Biao; Zhai, Hong-Ru; Caroline, G. Morgan
2015-04-01
A general model of a hybrid interfacial domain wall (HIDW) in ferromagnetic/antiferromagnetic exchange biased bilayers is proposed, where an interfacial domain wall is allowed to extend into either the ferromagnetic or antiferromagnetic layer or across both. The proposition is based on our theoretical investigation on thickness and field dependences of ferromagnetic domain wall (FMDW) and antiferromagnetic domain wall (AFDW), respectively. Good match of the simulation to the hysteresis loops of a series of NiFe/FeMn exchange-biased bilayers confirms the existence of the HIDW, where the AFDW part is found to preferentially occupy the entire antiferromagnetic layer while the FMDW shrinks with the increased magnetic field as expected. The observed asymmetry between the ascending and descending branches of the hysteresis loop is explained naturally as a consequence of different partition ratios between AFDW and FMDW. Project supported by the National Basic Research Program, China (Grant No. 2010CB923404), the National Natural Science Foundation for Young Scientists of China (Grant No. 61306121), and the China Postdoctoral Science Foundation (Grant No. 2013M541580).
Coupling between Current and Dynamic Magnetization : from Domain Walls to Spin Waves
Lucassen, M.E.
2012-01-01
So far, we have derived some general expressions for domain-wall motion and the spin motive force. We have seen that the β parameter plays a large role in both subjects. In all chapters of this thesis, there is an emphasis on the determination of this parameter. We also know how to incorporate therm
Axionic domain wall number related to U(1anom global symmetry
Directory of Open Access Journals (Sweden)
Jihn E. Kim
2016-08-01
Full Text Available The QCD axion with fa at an intermediate scale, 109 GeV∼1012 GeV, seems in conflict with the gravity spoil of global symmetries and may face the axionic domain wall problem. We point out that the string compactifications with an anomalous U(1 gauge symmetry, allowing desirable chiral matter spectra, circumvent these two problems simultaneously.
Domain wall pinning sites in Sm(CoFeCuZr) x magnets
Wong, Bunsen Y.; Willard, Matthew; Laughlin, David E.
1997-05-01
The magnetic domain structure of Sm(CoFeCuZr) x magnets was studied along various crystallographic zone axes with high resolution Focault mode Lorentz microscopy. The domain wall has been observed to be pinned at (1) 60° hexagonal (H) SmCo 5 cell boundaries, (2) features parallel to RSm 2Co 17c-axis, (3) features parallel to the RSm 2Co 17 basal plane, and (4) linear features with no specific crystallographic direction. The wall pinning features which are parallel to the c-axis were determined to be RSm 2Co 17 antiphase boundaries (APB) and possibly vertical section of HSmCo 5 cell boundaries. Both these microstructure features were found to have a higher Cu content than the RSm 2Co 17 matrix. This chemical inhomogeneity leads to local variations in magnetocrystalline anisotropy assists domain wall pinning, similar to the role of HSmCo 5 suggested previously. Since not all the domain wall pinning features observed are in a strained state, this suggested that chemical segregation to nanostructural features such as HSmCo 5 cell boundaries and APB play a more important role than coherency strain in determining Hci.
Domain wall pinning sites in Sm(CoFeCuZr){sub x} magnets
Energy Technology Data Exchange (ETDEWEB)
Wong, B.Y. [Pittsburgh Univ., PA (United States). Dept. of Materials Science and Engineering; Willard, M. [Pittsburgh Univ., PA (United States). Dept. of Materials Science and Engineering; Laughlin, D.E. [Pittsburgh Univ., PA (United States). Dept. of Materials Science and Engineering
1997-05-01
The magnetic domain structure of Sm(CoFeCuZr){sub x} magnets was studied along various crystallographic zone axes with high resolution Focault mode Lorentz microscopy. The domain wall has been observed to be pinned at (1) 60 hexagonal (H) SmCo{sub 5} cell boundaries, (2) features parallel to RSm{sub 2}Co{sub 17} c-axis, (3) features parallel to the RSm{sub 2}Co{sub 17} basal plane, and (4) linear features with no specific crystallographic direction. The wall pinning features which are parallel to the c-axis were determined to be RSm{sub 2}Co{sub 17} antiphase boundaries (APB) and possibly vertical section of HSmCo{sub 5} cell boundaries. Both these microstructure features were found to have a higher Cu content than the RSm{sub 2}Co{sub 17} matrix. This chemical inhomogeneity leads to local variations in magnetocrystalline anisotropy which assists domain wall pinning, similar to the role of HSmCo{sub 5} suggested previously. Since not all the domain wall pinning features observed are in a strained state, this suggested that chemical segregation to nanostructural features such as HSmCo{sub 5} cell boundaries and APB play a more important role than coherency strain in determining H{sub ci}. (orig.).
Domain walls in noncommutative gauge theories, folded D-branes, and communication with mirror world
Energy Technology Data Exchange (ETDEWEB)
Dubovsky, S.L.; Sibiryakov, S.M. E-mail: sibir@ms2.inr.ac.ru
2004-07-19
Noncommutative U(N) gauge theories at different N may be often thought of as different sectors of a single theory. For instance, U(1) theory possesses a sequence of vacua labeled by an integer parameter N, and the theory in the vicinity of the Nth vacuum coincides with the U(N) noncommutative gauge theory. We construct domain walls on noncommutative plane, which separate vacua with different gauge groups in gauge theory with adjoint scalar field. The scalar field has nonminimal coupling to the gauge field, such that the scale of noncommutativity is determined by the vacuum value of the scalar field. The domain walls are solutions of the BPS equations in the theory. It is natural to interprete the domain wall as a stack of D-branes plus a stack of folded D-branes. We support this interpretation by the analysis of small fluctuations around domain walls, and suggest that such configurations of branes emerge as solutions of the Matrix model in large class of pp-wave backgrounds with inhomogeneous field strength. We point out that the folded D-brane per se provides an explicit realization of the 'mirror world' idea, and speculate on some phenomenological consequences of this scenario.
Photonic realization of topologically protected bound states in domain-wall waveguide arrays
Lee-Thorp, James P; Xu, Xinan; Yang, Jinghui; Fefferman, Charles L; Wong, Chee Wei; Weinstein, Michael I
2016-01-01
We present an analytical theory of topologically protected photonic states for the two-dimensional Maxwell equations for a class of continuous periodic dielectric structures, modulated by a domain wall. We further numerically confirm the applicability of this theory for three-dimensional structures.
Nonadiabatic spin torque investigated using thermally activated magnetic domain wall dynamics
Eltschka, M.; Wötzel, M.; Rhensius, J.; Krzyk, S.; Nowak, U.; Kläui, M.; Kasama, T.; Dunin-Borkowski, R. E.; Heyderman, L. J.; van Driel, H.J.; Duine, R.A.
2010-01-01
Using transmission electron microscopy, we investigate the thermally activated motion of domain walls (DWs) between two positions in Permalloy (Ni80Fe20) nanowires at room temperature. We show that this purely thermal motion is well described by an Arrhenius law, allowing for a description of the DW
Solutions of the Ginsparg-Wilson relation and improved domain wall fermions
Bietenholz, W
1999-01-01
We discuss a number of lattice fermion actions solving the Ginsparg-Wilson relation. We also consider short ranged approximate solutions. In particular, we are interested in reducing the lattice artifacts, while avoiding (or suppressing) additive mass renormalization. In this context, we also arrive at a formulation of improved domain wall fermions.
Nonadiabatic Spin Torque Investigated Using Thermally Activated Magnetic Domain Wall Dynamics
DEFF Research Database (Denmark)
Eltschka, M.; Woetzel, Mathias; Rhensius, J.
2010-01-01
Using transmission electron microscopy, we investigate the thermally activated motion of domain walls (DWs) between two positions in Permalloy (Ni80Fe20) nanowires at room temperature. We show that this purely thermal motion is well described by an Arrhenius law, allowing for a description...
Nonsteady dynamic properties of a domain wall for the creep state under an alternating driving field
Zhou, N. J.; Zheng, B.
2014-07-01
With Monte Carlo simulations, the nonsteady dynamic properties of a domain wall have been systematically investigated for the thermally activated creep state under an alternating driving field. Taking the driven random-field Ising model in two dimensions as an example, two distinct growth stages of the domain interface are identified with both the correlation length and roughness function. One stage belongs to the universality class of the random depositions, and the other to that of the quenched Edwards-Wilkinson equation. In the latter case, due to the dynamic effect of overhangs, the domain interface may exhibit an intrinsic anomalous scaling behavior, different from that of the quenched Edwards-Wilkinson equation.
Some properties of domain wall solution in the Randall-Sundrum model
Ichinose, Shoichi
2001-12-01
Properties of the domain wall (kink) solution in the five-dimensional Randall-Sundrum model are examined both analytically and numerically. The configuration is derived by the bulk Higgs mechanism. We focus on (1) the convergence property of the solution, (2) the stablity of the solution, (3) the non-singular property of the Riemann curvature and (4) the behaviours of the warp factor and the Higgs field. It is found that the bulk curvature changes the sign around the surface of the wall. We also present some exact solutions for two simple cases: (a) the no-potential case, (b) the cosmological term-dominated case. Both solutions have the (naked) curvature singularity. We can regard the domain wall solution as a singularity resolution of the exact solutions.
Some Properties of Domain Wall Solution in the Randall-Sundrum Model
Ichinose, S
2001-01-01
Properties of the domain wall (kink) solution in the 5 dimensional Randall-Sundrum model are examined both {\\it analytically} and {\\it numerically}. The configuration is derived by the bulk Higgs mechanism. We focus on 1) the convergence property of the solution, 2) the stableness of the solution, 3) the non-singular property of the Riemann curvature, 4) the behaviours of the warp factor and the Higgs field. It is found that the bulk curvature changes the sign around the surface of the wall. We also present some {\\it exact} solutions for two simple cases: a) the no potential case, b) the cosmological term dominated case. Both solutions have the (naked) curvature singularity. We can regard the domain wall solution as a singularity resolution of the exact solutions.
Magnetic domain-wall velocity enhancement induced by a transverse magnetic field
Energy Technology Data Exchange (ETDEWEB)
Yang, Jusang, E-mail: jsyang@physics.utexas.edu [Department of Physics, The University of Texas at Austin, Austin, TX 78712-1081 (United States); Beach, Geoffrey S.D. [Department of Materials Science and Engineering, Massachusetts Institute of Technology, Cambridge, MA 02139 (United States); Knutson, Carl; Erskine, James L. [Department of Physics, The University of Texas at Austin, Austin, TX 78712-1081 (United States)
2016-01-01
Spin dynamics of field-driven domain walls (DWs) guided by permalloy nanowires are studied by high-speed magneto-optic polarimetry and numerical simulations. DW velocities and spin configurations are determined as functions of longitudinal drive field, transverse bias field, and nanowire width. Nanowires having cross-sectional dimensions large enough to support vortex wall structures exhibit regions of drive-field strength (at zero bias field) that have enhanced DW velocity resulting from coupled vortex structures that suppress oscillatory motion. Factor of 10 enhancements of the DW velocity are observed above the critical longitudinal drive-field (that marks the onset of oscillatory DW motion) when a transverse bias field is applied. Nanowires having smaller cross-sectional dimensions that support transverse wall structures also exhibit a region of higher mobility above the critical field, and similar transverse-field induced velocity enhancement but with a smaller enhancement factor. The bias-field enhancement of DW velocity is explained by numerical simulations of the spin distribution and dynamics within the propagating DW that reveal dynamic stabilization of coupled vortex structures and suppression of oscillatory motion in the nanowire conduit resulting in uniform DW motion at high speed. The enhanced velocity and drive field range are achieved at the expense of a less compact DW spin distribution. - Highlights: • The transverse magnetic fields can dramatically enhance the domain wall velocity. • The numerical simulation exhibits the four distinct dynamic modes. • Coupled multiple vortex structures within the domain wall become dynamically stable. • The enhanced domain wall velocity is explained by numerical simulations.
Transverse and vortex domain wall structure in magnetic nanowires with uniaxial in-plane anisotropy.
Bryan, M T; Bance, S; Dean, J; Schrefl, T; Allwood, D A
2012-01-18
Micromagnetic and analytical models are used to investigate how in-plane uniaxial anisotropy affects transverse and vortex domain walls in nanowires where shape anisotropy dominates. The effect of the uniaxial anisotropy can be interpreted as a modification of the effective wire dimensions. When the anisotropy axis is aligned with the wire axis (θ(a) = 0), the wall width is narrower than when no anisotropy is present. Conversely, the wall width increases when the anisotropy axis is perpendicular to the wire axis (θ(a) = π/2). The anisotropy also affects the nanowire dimensions at which transverse walls become unstable. This phase boundary shifts to larger widths or thicknesses when θ(a) = 0, but smaller widths or thicknesses when θ(a) = π/2.
Energy Technology Data Exchange (ETDEWEB)
Ueda, K.; Koyama, T.; Hiramatsu, R.; Kobayashi, K.; Ono, T. [Institute for Chemical Research, Kyoto University, Gokasho, Uji, Kyoto 611-0011 (Japan); Chiba, D. [Institute for Chemical Research, Kyoto University, Gokasho, Uji, Kyoto 611-0011 (Japan); PRESTO, Japan Science and Technology Agency, 4-1-8 Honcho Kawaguchi, Saitama 322-0012 (Japan); Fukami, S. [Green Innovation Research Laboratories, NEC Corporation, 34 Miyukigaoka, Tsukuba, Ibaraki 305-8501 (Japan); Center for Spintronics Integrated Systems, Tohoku University, 2-1-1 Katahira, Aoba-ku, Sendai 980-8577 (Japan); Tanigawa, H.; Suzuki, T. [RENESAS Electronics Corporation, Sagamihara, Kanagawa 252-5298 (Japan); Ohshima, N. [NEC Energy Device Ltd., 1120 Shimokuzawa, Chuo-ku, Sagamihara, Kanagawa 252-5298 (Japan); Ishiwata, N. [Green Innovation Research Laboratories, NEC Corporation, 34 Miyukigaoka, Tsukuba, Ibaraki 305-8501 (Japan); Nakatani, Y. [University of Electro-communications, Chofu, Tokyo 182-8585 (Japan)
2012-05-14
We have investigated the temperature dependence of the current-induced magnetic domain wall (DW) motion in a perpendicularly magnetized Co/Ni nanowire at various temperatures and with various applied currents. The carrier spin polarization was estimated from the measured domain wall velocity. We found that it decreased more with increasing temperature from 100 K to 530 K than the saturation magnetization did.
Evolution of defect signatures at ferroelectric domain walls in Mg-doped LiNbO{sub 3}
Energy Technology Data Exchange (ETDEWEB)
Nataf, Guillaume F. [Materials, Research and Technology Department, Luxembourg Institute of Science and Technology, 41 Rue du Brill, 4422, Belvaux (Luxembourg); Service de Physique de l' Etat Condense, DSM/IRAMIS/SPEC, CNRS UMR 3680, CEA Saclay, 91191, Gif sur Yvette cedex (France); Guennou, Mael [Materials, Research and Technology Department, Luxembourg Institute of Science and Technology, 41 Rue du Brill, 4422, Belvaux (Luxembourg); Haussmann, Alexander [Institut fuer Angewandte Photophysik, Technische Universitaet Dresden, George-Baehr-Str. 1, 01069, Dresden (Germany); Barrett, Nick [Service de Physique de l' Etat Condense, DSM/IRAMIS/SPEC, CNRS UMR 3680, CEA Saclay, 91191, Gif sur Yvette cedex (France); Kreisel, Jens [Materials, Research and Technology Department, Luxembourg Institute of Science and Technology, 41 Rue du Brill, 4422, Belvaux (Luxembourg); Physics and Materials Science Research Unit, University of Luxembourg, 41 Rue du Brill, 4422, Belvaux (Luxembourg)
2016-03-15
The domain structure of uniaxial ferroelectric lithium niobate single crystals is investigated using Raman spectroscopy mapping. The influence of doping with magnesium and poling at room temperature is studied by analysing frequency shifts at domain walls and their variations with dopant concentration and annealing conditions. It is shown that defects are stabilized at domain walls and that changes in the defect structures with Mg concentration can be probed by the shift of Raman modes. We show that the signatures of polar defects in the bulk and at the domain walls differ. (copyright 2016 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)
Tunneling decay of false domain walls: the silence of the lambs
Haberichter, Mareike; Paranjape, M B; Ung, Yvan
2015-01-01
We study the decay of "false" domain walls, which are metastable states of the quantum theory where the true vacuum is trapped inside the wall, with the false vacuum outside. We consider a theory with two scalar fields, a shepherd field and a field of sheep. The shepherd field serves to herd the solitons of the sheep field so that they are nicely bunched together. However, quantum tunnelling of the shepherd field releases the sheep to spread out uncontrollably. We show how to calculate the tunnelling amplitude for such a disintegration.
Tunneling decay of false domain walls: The silence of the lambs
Energy Technology Data Exchange (ETDEWEB)
Haberichter, Mareike, E-mail: M.Haberichter@kent.ac.uk [Department of Applied Mathematics and Theoretical Physics, University of Cambridge, Wilberforce Road, Cambridge CB3 0WA (United Kingdom); School of Mathematics, Statistics and Actuarial Science, University of Kent, Canterbury CT2 7NF (United Kingdom); MacKenzie, Richard, E-mail: richard.mackenzie@umontreal.ca; Ung, Yvan, E-mail: klingon-ecology@hotmail.com [Groupe de Physique des Particules, Département de Physique, Université de Montréal, C.P. 6128, Succursale Centre-ville, Montreal, Québec H3C 3J7 (Canada); Paranjape, M. B., E-mail: paranj@lps.umontreal.ca [Department of Applied Mathematics and Theoretical Physics, University of Cambridge, Wilberforce Road, Cambridge CB3 0WA (United Kingdom); Groupe de Physique des Particules, Département de Physique, Université de Montréal, C.P. 6128, Succursale Centre-ville, Montreal, Québec H3C 3J7 (Canada); St. John’s College, University of Cambridge, Cambridge CB2 1TP (United Kingdom)
2016-04-15
We study the decay of “false” domain walls, that is, metastable states of the quantum theory where the true vacuum is trapped inside the wall with the false vacuum outside. We consider a theory with two scalar fields, a shepherd field and a field of sheep. The shepherd field serves to herd the solitons of the sheep field so that they are nicely bunched together. However, quantum tunnelling of the shepherd field releases the sheep to spread out uncontrollably. We show how to calculate the tunnelling amplitude for such a disintegration.
Optimized cobalt nanowires for domain wall manipulation imaged by in situ Lorentz microscopy
Energy Technology Data Exchange (ETDEWEB)
Rodriguez, L. A. [Laboratorio de Microscopias Avanzadas (LMA), Instituto de Nanociencia de Aragon (INA), Universidad de Zaragoza, 50018 Zaragoza (Spain); Departamento de Fisica de la Materia Condensada, Universidad de Zaragoza, 50009 Zaragoza (Spain); Transpyrenean Associated Laboratory for Electron Microscopy (TALEM), CEMES-INA, CNRS-Universidad de Zaragoza, Toulouse (France); CEMES-CNRS 29, rue Jeanne Marvig, B.P. 94347 F-31055, Toulouse Cedex (France); Magen, C. [Laboratorio de Microscopias Avanzadas (LMA), Instituto de Nanociencia de Aragon (INA), Universidad de Zaragoza, 50018 Zaragoza (Spain); Departamento de Fisica de la Materia Condensada, Universidad de Zaragoza, 50009 Zaragoza (Spain); Transpyrenean Associated Laboratory for Electron Microscopy (TALEM), CEMES-INA, CNRS-Universidad de Zaragoza, Toulouse (France); Fundacion ARAID, 50004 Zaragoza (Spain); Snoeck, E.; Gatel, C. [Transpyrenean Associated Laboratory for Electron Microscopy (TALEM), CEMES-INA, CNRS-Universidad de Zaragoza, Toulouse (France); CEMES-CNRS 29, rue Jeanne Marvig, B.P. 94347 F-31055, Toulouse Cedex (France); Serrano-Ramon, L. [Departamento de Fisica de la Materia Condensada, Universidad de Zaragoza, 50009 Zaragoza (Spain); Instituto de Ciencia de Materiales de Aragon (ICMA), Universidad de Zaragoza-CSIC, 50009 Zaragoza (Spain); and others
2013-01-14
Direct observation of domain wall (DW) nucleation and propagation in focused electron beam induced deposited Co nanowires as a function of their dimensions was carried out by Lorentz microscopy (LTEM) upon in situ application of magnetic field. Optimal dimensions favoring the unambiguous DW nucleation/propagation required for applications were found in 500-nm-wide and 13-nm-thick Co nanowires, with a maximum nucleation field and the largest gap between nucleation and propagation fields. The internal DW structures were resolved using the transport-of-intensity equation formalism in LTEM images and showed that the optimal nanowire dimensions correspond to the crossover between the nucleation of transverse and vortex walls.
Gravitational domain walls and the dynamics of the gravitational constant G
Bunster, Claudio; Gomberoff, Andrés
2017-07-01
From the point of view of elementary particle physics, the gravitational constant G is extraordinarily small. This has led to asking whether it could have decayed to its present value from an initial one commensurate with microscopical units. A mechanism that leads to such a decay is proposed herein. It is based on assuming that G may take different values within regions of the universe separated by a novel kind of domain wall, a "G -wall." The idea is implemented by introducing a gauge potential Aμ ν ρ, and its conjugate D , which determines the value of G as an integration constant rather than a fundamental constant. The value of G jumps when one goes through a G -wall. The procedure extends one previously developed for the cosmological constant, but the generalization is far from straightforward: (i) The intrinsic geometry of a G -wall is not the same as seen from its two sides because the second law of black hole thermodynamics mandates that the jump in G must cause a discontinuity in the scale of length. (ii) The size of the decay step in G is controlled by a function G (D ) which may be chosen so as to diminish the value of G towards the asymptote G =0 . It is shown that: (i) The dynamics of the gravitational field with G treated as a dynamical variable, coupled to G -walls and matter, follows from an action principle, which is given. (ii) A particle that impinges on a G -wall may be refracted or reflected. (iii) The various forces between two particles change when a G -wall is inserted in between them. (iv) G -walls may be nucleated trough tunneling and thermal effects, whose semiclassical probabilities are evaluated. (v) If the action principle is constructed properly, the entropy of a black hole increases when the value of the gravitational constant is changed through the absorption of a G-wall by the hole.
Localization and chiral symmetry in 2+1 flavor domain wall QCD
Antonio, David J; Boyle, Peter A; Christ, Norman H; Clark, Michael A; Cohen, Saul D; Dawson, Chris; Hart, Alistair; Joó, Balint; Jung, Chulwoo; Kenway, Richard D; Li, Shu; Lin, Meifeng; Mawhinney, Robert D; Maynard, Christopher M; Ohta, Shigemi; Tweedie, Robert J; Yamaguchi, Azusa
2007-01-01
We present results for the dependence of the residual mass of domain wall fermions (DWF) on the size of the fifth dimension and its relation to the density and localization properties of low-lying eigenvectors of the corresponding hermitian Wilson Dirac operator for 2+1 flavor domain wall QCD. Using the DBW2 and Iwasaki gauge actions, we generate ensembles of configurations with a $16^3\\times 32$ space-time volume and an extent of 8 in the fifth dimension for the sea quarks. We demonstrate the existence of a regime where the degree of locality, the size of chiral symmetry breaking and the rate of topology change can be acceptable for inverse lattice spacings $a^{-1} \\ge 1.6$ GeV.
Kondo effect from a Lorentz-violating domain wall description of superconductivity
Bazeia, D; Mota-Silva, J C
2016-01-01
We extend recent results on domain wall description of superconductivity in an Abelian Higgs model by introducing a particular Lorentz-violating term. The temperature of the system is interpreted through the fact that the soliton following accelerating orbits is a Rindler observer experiencing a thermal bath. We show that this term can be associated with the {\\sl Kondo effect}, that is, the Lorentz-violating parameter is closely related to the concentration of magnetic impurities living on a superconducting domain wall. We also found that the critical temperature decreasing with the impurity concentration as a non-single valued function, for the case $T_K
Perterbative O(asa) matching in static heavy and domain-wall light quark system
Energy Technology Data Exchange (ETDEWEB)
Ishikawa,T.
2008-07-14
We discuss the perturbative O(a{sub s}a) matching in the static heavy and domain-wall light quark system. The gluon action is the Iwasaki action and the link smearing is performed in the static heavy action. The chiral symmetry of the light quark realized by using the domain-wall fermion formulation does not prohibit the mixing of the operators at O(a). The application of O(a) improvement to the actual data shows that the B meson decay constant f{sub B}, the matrix elements M{sub B} and the B parameter B{sub B} have non-negligible effects, while the effect on the SU(3) breaking ratio {zeta} is small.
Using domain walls to perform non-local measurements with high spin signal amplitudes
Savero Torres, W.; Pham, V.-T.; Zahnd, G.; Laczkowski, P.; Nguyen, V.-D.; Beigné, C.; Notin, L.; Jamet, M.; Marty, A.; Vila, L.; Attané, J.-P.
2016-07-01
Standard non-local measurements require lateral spin-valves with two different ferromagnetic electrodes, to create and to detect the spin accumulation. Here we show that non-local measurements can also be performed in a cross-shaped nanostructure, made of a single ferromagnetic wire connected to an orthogonal non-magnetic wire. A magnetic domain wall located underneath the ferromagnetic/non-magnetic interface is used to control the magnetizations of the injection and detection zones. As these zones can be very close, our results display spin signals possessing amplitudes larger than those obtained in conventional non-local measurements. We also show that this method can be used as a domain wall detection technique.
Domain wall pinning on strain relaxation defects in FePt(001)/Pt thin films
Energy Technology Data Exchange (ETDEWEB)
Attane, J. P.; Samson, Y.; Marty, A.; Halley, D.; Beigne, C.
2001-08-06
Thin FePt (001) films, grown by molecular-beam epitaxy on Pt(001), exhibit a very large perpendicular magnetic anisotropy (K{sub u}=5 x 10{sup 6}Jm{sup -3}) and a 100% magnetic remanence in perpendicular field. The lattice misfit between FePt and Pt (1.5%) relaxes through the pileup of a/6 <112> partial dislocations along {l_brace}111{r_brace} planes, leading to the formation of microtwins. Atomic force microscopy images demonstrate that this process induces a spontaneous rectangular nanostructuration of the sample, while magnetic force microscopy shows that the microtwins act as pinning sites for the magnetic walls. This leads to square magnetic domains and explains the large coercivity associated with the domain wall propagation. {copyright} 2001 American Institute of Physics.
Domain wall pinning on strain relaxation defects in FePt(001)/Pt thin films
Attané, J. P.; Samson, Y.; Marty, A.; Halley, D.; Beigné, C.
2001-08-01
Thin FePt (001) films, grown by molecular-beam epitaxy on Pt(001), exhibit a very large perpendicular magnetic anisotropy (Ku=5×106J m-3) and a 100% magnetic remanence in perpendicular field. The lattice misfit between FePt and Pt (1.5%) relaxes through the pileup of a/6 partial dislocations along {111} planes, leading to the formation of microtwins. Atomic force microscopy images demonstrate that this process induces a spontaneous rectangular nanostructuration of the sample, while magnetic force microscopy shows that the microtwins act as pinning sites for the magnetic walls. This leads to square magnetic domains and explains the large coercivity associated with the domain wall propagation.
Domain wall interactions due to vacuum Dirac field fluctuations in 2 +1 dimensions
Fosco, C. D.; Mazzitelli, F. D.
2016-07-01
We evaluate quantum effects due to a two-component Dirac field in 2 +1 spacetime dimensions, coupled to domain-wall-like defects with a smooth shape. We show that these effects induce nontrivial contributions to the (shape-dependent) energy of the domain walls. For a single defect, we study the divergences in the corresponding self-energy, and also consider the role of the massless zero mode—corresponding to the Callan-Harvey mechanism—by coupling the Dirac field to an external gauge field. For two defects, we show that the Dirac field induces a nontrivial, Casimir-like effect between them, and we provide an exact expression for that interaction in the case of two straight-line parallel defects. As is the case for the Casimir interaction energy, the result is finite and unambiguous.
Localization and chiral symmetry in 2+1 flavor domain wall QCD
Energy Technology Data Exchange (ETDEWEB)
David J. Antonio; Kenneth C. Bowler; Peter A. Boyle; Norman H. Christ; Michael A. Clark; Saul D. Cohen; Chris Dawson; Alistair Hart; Balint Joó; Chulwoo Jung; Richard D. Kenway; Shu Li; Meifeng Lin; Robert D. Mawhinney; Christopher M. Maynard; Shigemi Ohta; Robert J. Tweedie; Azusa Yamaguchi
2008-01-01
We present results for the dependence of the residual mass of domain wall fermions (DWF) on the size of the fifth dimension and its relation to the density and localization properties of low-lying eigenvectors of the corresponding hermitian Wilson Dirac operator relevant to simulations of 2+1 flavor domain wall QCD. Using the DBW2 and Iwasaki gauge actions, we generate ensembles of configurations with a $16^3\\times 32$ space-time volume and an extent of 8 in the fifth dimension for the sea quarks. We demonstrate the existence of a regime where the degree of locality, the size of chiral symmetry breaking and the rate of topology change can be acceptable for inverse lattice spacings $a^{-1} \\ge 1.6$ GeV.
Current induced domain wall motion in nanostripes with perpendicular magnetic anisotropy
Energy Technology Data Exchange (ETDEWEB)
Noh, Su Jung; Tan, Reasmey P.; Chun, Byong Sun [Department of Materials Science and Engineering, Korea University, Seoul 136-713 (Korea, Republic of); Kim, Young Keun, E-mail: ykim97@korea.ac.k [Department of Materials Science and Engineering, Korea University, Seoul 136-713 (Korea, Republic of)
2010-11-15
We report micromagnetic modeling results of current induced domain wall (DW) motion in magnetic devices with perpendicular magnetic anisotropy by solving the Landau-Lifschitz-Gilbert equation including adiabatic and non-adiabatic terms. A nanostripe model system with dimensions of 500 nm (L)x25 nm (W)x5 nm (H) was selected for calculating the DW motion and its width, as a function of various parameters such as non-adiabatic contribution, anisotropy constant (K{sub u}), saturation magnetization (M{sub s}), and temperature (T). The DW velocity was found to increase when the values of K{sub u} and T were increased and the M{sub s} value decreased. In addition, a reduction of the domain wall width could be achieved by increasing K{sub u} and lowering M{sub s} values regardless of the non-adiabatic constant value.
Partial Breaking of Three-Fold Symmetry via Percolation of a Domain Wall
Bhattacharya, Soumyadeep
2016-01-01
We show that suppression of vortex strings splits the order-disorder transition in the three-state Potts ferromagnet on a simple cubic lattice and opens up an intermediate phase characterized by partial breaking of the three-fold symmetry and long-range order. In contrast, suppression of vortices in the same model on a square lattice results in an intermediate phase with enhanced U(1) symmetry and quasi-long-range order. We show that the difference between the two phases originates from distinct patterns of domain wall proliferation. A domain wall, separating the two most populous spin states, percolates on its own in the former phase but remains at a percolation threshold in the latter.
The Stability of Fake Flat Domain Walls on Kähler Manifold
Akbar, F. T.; Wijaya, R. N.; Gunara, B. E.
2016-08-01
In this paper, we study the stability of flat fake domain walls solution of fake N = 1 supergravity in d + 1 dimensions with Kahler surface as the sigma model. We start with Lagrangian for N = 1 fake supergravity which is coupling between gravity and complex scalar in d + 1 dimensions with scalar potential turned on. Then, as in supergravity theory, we demand that the scalar fields span the Kahler manifold. The equations of motion for fields can be reduced into first order equations by defining the superpotential and the resulting equations are called the projection equation and the fake BPS equation. Finally, we discuss about the stability of flat fake domain walls by investigating the critical points of the superpotential and the scalar potential.
πK scattering in full QCD with domain-wall valence quarks
Beane, Silas R.; Bedaque, Paulo F.; Luu, Thomas C.; Orginos, Kostas; Pallante, Elisabetta; Parreño, Assumpta; Savage, Martin J.
2006-01-01
We calculate the π+K+ scattering length in fully-dynamical lattice QCD with domain-wall valence quarks on MILC lattices with rooted staggered sea-quarks at a lattice spacing of b = 0.125 fm, lattice spatial size of L = 2.5 fm and at pion masses of mπ ~ 290, 350, 490 and 600 MeV. The lattice data, an
Energy Technology Data Exchange (ETDEWEB)
BLUM,T.; SONI,A.
2007-03-15
The workshop was held to mark the 10th anniversary of the first numerical simulations of QCD using domain wall fermions initiated at BNL. It is very gratifying that in the intervening decade widespread use of domain wall and overlap fermions is being made. It therefore seemed appropriate at this stage for some ''communal introspection'' of the progress that has been made, hurdles that need to be overcome, and physics that can and should be done with chiral fermions. The meeting was very well attended, drawing about 60 registered participants primarily from Europe, Japan and the US. It was quite remarkable that pioneers David Kaplan, Herbert Neuberger, Rajamani Narayanan, Yigal Shamir, Sinya Aoki, and Pavlos Vranas all attended the workshop. Comparisons between domain wall and overlap formulations, with their respective advantages and limitations, were discussed at length, and a broad physics program including pion and kaon physics, the epsilon regime, nucleon structure, and topology, among others, emerged. New machines and improved algorithms have played a key role in realizing realistic dynamical fermion lattice simulations (small quark mass, large volume, and so on), so much in fact that measurements are now as costly. Consequently, ways to make the measurements more efficient were also discussed. We were very pleased to see the keen and ever growing interest in chiral fermions in our community and the significant strides our colleagues have made in bringing chiral fermions to the fore of lattice QCD calculations. Their contributions made the workshop a success, and we thank them deeply for sharing their time and ideas. Finally, we must especially acknowledge Norman Christ and Bob Mawhinney for their early and continued collaboration without which the success of domain wall fermions would not have been possible.
Integral formula for elliptic SOS models with domain walls and a reflecting end
Lamers, Jules
2015-12-01
In this paper we extend previous work of Galleas and the author to elliptic SOS models. We demonstrate that the dynamical reflection algebra can be exploited to obtain a functional equation characterizing the partition function of an elliptic SOS model with domain-wall boundaries and one reflecting end. Special attention is paid to the structure of the functional equation. Through this approach we find a novel multiple-integral formula for that partition function.
Domain wall motions in perpendicularly magnetized CoFe/Pd multilayer nanowire
DEFF Research Database (Denmark)
Meng, Zhaoliang; Kumar, Manoj; Qiu, Jinjun;
2014-01-01
Current-induced domain wall (DW) motion is investigated in a 600nm wide nanowire using multilayer film with a structure of Ta(5nm)/Pd(5nm)/[CoFe(0.4nm)/Pd(1.2nm)]15/Ta(5nm) in terms of anomalous Hall effect measurements. It is found that motion of DWs can be driven by a current density as low as 1...
On-Chip Manipulation of Protein-Coated Magnetic Beads via Domain-Wall Conduits
DEFF Research Database (Denmark)
Donolato, Marco; Vavassori, Paolo; Gobbi, Marco;
2010-01-01
Geometrically constrained magnetic domain walls (DWs) in magnetic nanowires can be manipulated at the nanometer scale. The inhomogeneous magnetic stray field generated by a DW can capture a magnetic nanoparticle in solution. On-chip nanomanipulation of individual magnetic beads coated with proteins...... is demonstrated through the motion of geometrically constrained DWs in specially designed magnetic nanoconduits fully integrated in a lab-on-a-chip platform....
Observation of galvanomagnetic voltages at a magnetic domain wall in Ni-Fe films
Gopalaswamy, S.; Berger, L.
1991-11-01
A Ni81Fe19 film of 110 nm thickness is traversed by a dc current density normal to the easy axis. Two sharp tungsten wires serve as potential probes, distant by 210 μm along the easy axis. A charged wall, oriented at an angle to the easy axis, is made to creep slowly across the sample by applying dc easy axis and 60-Hz hard axis magnetic fields. The dc voltage between the probes is found to vary whenever the wall passes by the probes. The variation has the form of a voltage peak of ≂40 μV typical height. These peaks are caused by the planar Hall effect, in combination with a canting of the domain magnetization near the charged wall. In the case of a current parallel to the easy axis and normal to the line joining the probes, a steplike voltage variation ≤150 μV is observed for an uncharged wall in the presence of a dc hard axis field. Planar Hall effect and (field induced) domain canting are again responsible.
An investigation of time-dependent domain wall pinning effects in Tb/Fe multilayer thin flms
Phillips, G.N.; O'Grady, K.; El-Hilo, M.
2002-01-01
Reverse domain nucleation time measurements have been performed on two Tb/Fe multilayer magneto-optic films exhibiting different degrees of domain wall pinning.A linear relationship between ln (reverse domain nucleation time) and the applied field has been predicted and observed for a sample exhibit
Microscopic Raman spectroscopy in the vicinity of domain wall of (Na,K)NbO3 piezoelectrics
Taniguchi, Yuya; Kakimoto, Ken-ichi
2015-10-01
The domain walls of Mn-doped (Na,K)NbO3 (NKN) crystals and ceramics have been measured by spectroscopy methods. Microscopy-Raman and infrared (IR) spectroscopies were performed vertically to lamellar domain structures by line mapping. Regarding the crystals, large changes were confirmed in the vicinity of domain walls. Both the Raman shift and the peak intensity at approximately 600 cm-1, which include the symmetric stretching modes of the oxygen octahedron, were observed. Similar changes were also characterized for electrically polarized NKN ceramics. In addition, the permittivity of NKN crystals increased in the vicinity of the domain wall, which was measured by IR spectroscopy. These results were attributed to the changes in the oxygen octahedron structures due to local changes in spontaneous polarization directions in the vicinity of the domain walls.
Nagatani, Y
2001-01-01
A spherical domain wall around a small black hole is formed by the Hawking radiation from the black hole in the symmetry-broken-phase of the field theory, e.g., the Standard Model (SM) and the Grand Unified Theory (GUT) which have a property of the phase transition. We have obtained two types of the spherical domain wall; (a) thermalized wall which is formed by the local heating up near black hole and symmetry restore locally and (b) dynamical wall which is formed by the balance between the pressure from the Hawking radiation and the pressure from the wall tensions. The electroweak wall is formed as a thermalized wall around a black hole with mass of the several hundred kilogram. The GUT wall is formed as a dynamical wall around much smaller black hole. The electroweak wall around a black hole can produce baryon number by the assumption of the CP-broken phase in the wall. The GUT wall can supply charge into the black hole, namely, the wall causes the spontaneous charging up of the black hole. We propose a cos...
Wang, Yi; Nelson, Chris; Melville, Alexander; Winchester, Benjamin; Shang, Shunli; Liu, Zi-Kui; Schlom, Darrell G; Pan, Xiaoqing; Chen, Long-Qing
2013-06-28
We determined the atomic structures and energies of 109°, 180°, and 71° domain walls in BiFeO3, combining density functional theory+U calculations and aberration-corrected transmission electron microscopy images. We find a substantial Bi sublattice shift and a rather uniform Fe sublattice across the walls. The calculated wall energies (γ) follow the sequence γ109<γ180<γ71 for the 109°, 180°, and 71° walls. We attribute the high 71° wall energy to an opposite tilting rotation of the oxygen octahedra and the low 109° wall energy to the opposite twisting rotation of the oxygen octahedra across the domain walls.
Magnetoresistive waves in plasmas
Felber, F. S.; Hunter, R. O., Jr.; Pereira, N. R.; Tajima, T.
1982-10-01
The self-generated magnetic field of a current diffusing into a plasma between conductors can magnetically insulate the plasma. Propagation of magnetoresistive waves in plasmas is analyzed. Applications to plasma opening switches are discussed.
Domain Walls, near-BPS Bubbles and Probabilities in the Landscape
Energy Technology Data Exchange (ETDEWEB)
Ceresole, Anna; /INFN, Turin /Turin U.; Dall' Agata, Gianguido; /CERN; Giryavets, Alexander; Kallosh, Renata; Linde, Andrei; /Stanford U., Phys. Dept.
2006-06-27
We develop a theory of static BPS domain walls in stringy landscape and present a large family of BPS walls interpolating between different supersymmetric vacua. Examples include KKLT models, STU models, type IIB multiple flux vacua, and models with several Minkowski and AdS vacua. After the uplifting, some of the vacua become dS, whereas some others remain AdS. The near-BPS walls separating these vacua may be seen as bubble walls in the theory of vacuum decay. As an outcome of our investigation of the BPS walls, we found that the decay rate of dS vacua to a collapsing space with a negative vacuum energy can be quite large. The parts of space that experience a decay to a collapsing space, or to a Minkowski vacuum, never return back to dS space. The channels of irreversible vacuum decay serve as sinks for the probability flow. The existence of such sinks is a distinguishing feature of the landscape. We show that it strongly affects the probability distributions in string cosmology.
The mechanism of domain-wall structure formation in Ar-Kr submonolayer films on graphite
Directory of Open Access Journals (Sweden)
A. Patrykiejew
2014-12-01
Full Text Available Using Monte Carlo simulation method in the canonical ensemble, we have studied the commensurate-incommensurate transition in two-dimensional finite mixed clusters of Ar and Kr adsorbed on graphite basal plane at low temperatures. It has been demonstrated that the transition occurs when the argon concentration exceeds the value needed to cover the peripheries of the cluster. The incommensurate phase exhibits a similar domain-wall structure as observed in pure krypton films at the densities exceeding the density of a perfect (√3x√3R30º commensurate phase, but the size of commensurate domains does not change much with the cluster size. When the argon concentration increases, the composition of domain walls changes while the commensurate domains are made of pure krypton. We have constructed a simple one-dimensional Frenkel-Kontorova-like model that yields the results being in a good qualitative agreement with the Monte Carlo results obtained for two-dimensional systems.
Shield-related signal instability in magnetoresistive heads
Nakamoto, K.; Narumi, S.; Kawabe, T.; Kobayashi, T.; Fukui, H.
1999-04-01
Magnetoresistive (MR) heads with various upper shield materials were fabricated and their read-write performance was tested to clarify the shield-related effect on the signal instability in MR heads. Comparison of a head with an upper shield layer of higher magnetostriction and one with lower magnetostriction showed that the latter had better stability in the output signal of a repeated read-write test. The output amplitude of a head with an upper shield layer of Co52Ni27Fe21 film, which had a high magnetostriction of about +3×10-6, was varied by applying a low external longitudinal field, which affected just the shield layers. This change in the output corresponded well to the output variation in the repeated read-write test. The spin scanning electron micrograph image of this head revealed a distinct domain wall in the air bearing surface near the MR sensor. These results indicated that instability of the domain structure in a shield layer was one of the causes of the signal instability in MR heads; an unusual bias field from a domain wall of the shield layer, which could be moved easily by a repeated writing operation, caused a variation in the biased state of the MR layer which resulted in the signal variation, and that low magnetostriction was required for a shield material to achieve a stable head.
Néel walls between tailored parallel-stripe domains in IrMn/CoFe exchange bias layers
Energy Technology Data Exchange (ETDEWEB)
Ueltzhöffer, Timo, E-mail: timo.ueltzhoeffer@physik.uni-kassel.de; Schmidt, Christoph; Ehresmann, Arno [Institute of Physics and Center for Interdisciplinary Nanostructure Science and Technology (CINSaT), University of Kassel, Heinrich-Plett-Str. 40, 34132 Kassel (Germany); Krug, Ingo [Peter Gruenberg Institute and JARA-FIT, FZ Juelich, D-52425 Juelich (Germany); Institut für Optik und Atomare Physik, Technische Universität Berlin, Berlin (Germany); Nickel, Florian; Gottlob, Daniel [Peter Gruenberg Institute and JARA-FIT, FZ Juelich, D-52425 Juelich (Germany)
2015-03-28
Tailored parallel-stripe magnetic domains with antiparallel magnetizations in adjacent domains along the long stripe axis have been fabricated in an IrMn/CoFe Exchange Bias thin film system by 10 keV He{sup +}-ion bombardment induced magnetic patterning. Domain walls between these domains are of Néel type and asymmetric as they separate domains of different anisotropies. X-ray magnetic circular dichroism asymmetry images were obtained by x-ray photoelectron emission microscopy at the Co/Fe L{sub 3} edges at the synchrotron radiation source BESSY II. They revealed Néel-wall tail widths of 1 μm in agreement with the results of a model that was modified in order to describe such walls. Similarly obtained domain core widths show a discrepancy to values estimated from the model, but could be explained by experimental broadening. The rotation senses in adjacent walls were determined, yielding unwinding domain walls with non-interacting walls in this layer system.
Zsurzsa, S.; Péter, L.; Kiss, L. F.; Bakonyi, I.
2017-01-01
The magnetic properties and the magnetoresistance behavior were investigated for electrodeposited nanoscale Co films, Co/Cu/Co sandwiches and Co/Cu multilayers with individual Co layer thicknesses ranging from 1 nm to 20 nm. The measured saturation magnetization values confirmed that the nominal and actual layer thicknesses are in fairly good agreement. All three types of layered structure exhibited anisotropic magnetoresistance for thick magnetic layers whereas the Co/Cu/Co sandwiches and Co/Cu multilayers with thinner magnetic layers exhibited giant magnetoresistance (GMR), the GMR magnitude being the largest for the thinnest Co layers. The decreasing values of the relative remanence and the coercive field when reducing the Co layer thickness down to below about 3 nm indicated the presence of superparamagnetic (SPM) regions in the magnetic layers which could be more firmly evidenced for these samples by a decomposition of the magnetoresistance vs. field curves into a ferromagnetic and an SPM contribution. For thicker magnetic layers, the dependence of the coercivity (Hc) on magnetic layer thickness (d) could be described for each of the layered structure types by the usual equation Hc=Hco+a/dn with an exponent around n=1. The common value of n suggests a similar mechanism for the magnetization reversal by domain wall motion in all three structure types and hints also at the absence of coupling between magnetic layers in the Co/Cu/Co sandwiches and Co/Cu multilayers.
Role of spin diffusion in current-induced domain wall motion for disordered ferromagnets
Akosa, Collins Ashu
2015-03-12
Current-induced spin transfer torque and magnetization dynamics in the presence of spin diffusion in disordered magnetic textures is studied theoretically. We demonstrate using tight-binding calculations that weak, spin-conserving impurity scattering dramatically enhances the nonadiabaticity. To further explore this mechanism, a phenomenological drift-diffusion model for incoherent spin transport is investigated. We show that incoherent spin diffusion indeed produces an additional spatially dependent torque of the form ∼∇2[m×(u⋅∇)m]+ξ∇2[(u⋅∇)m], where m is the local magnetization direction, u is the direction of injected current, and ξ is a parameter characterizing the spin dynamics (precession, dephasing, and spin-flip). This torque, which scales as the inverse square of the domain wall width, only weakly enhances the longitudinal velocity of a transverse domain wall but significantly enhances the transverse velocity of vortex walls. The spatial-dependent spin transfer torque uncovered in this study is expected to have significant impact on the current-driven motion of abrupt two-dimensional textures such as vortices, skyrmions, and merons.
The dynamics of field and current-driven magnetic domain wall depinning
Beach, Geoffrey; Knutson, Carl; Tsoi, Maxim; Erskine, James
2008-03-01
The depinning of a magnetic domain wall from a well-defined potential well was studied experimentally on timescales ranging from minutes down to tens of nanoseconds. At longer timescales, the behavior follows the classical Neel-Brown model of thermal activation, one of the few observations of this process for the ideal case of a single energy barrier. Below one microsecond, however, the depinning rate becomes independent of the activation volume and assumes a more universal behavior. This transition is due to a vanishing of the energy barrier at a critical field, beyond which the rate of depinning depends primarily on the torque supplied by the field and spin current. A dc spin-polarized current flowing across the domain wall has the effect of lowering the energy barrier by an amount that is predominantly quadratic in current, independent of its direction. This is seen to arise from a shift of the wall in the energy potential due to the adiabatic component of spin-transfer torque.
Chan, Brigitte
2010-04-01
DRDC Ottawa is investigating high resolution synthetic aperture radar (SAR) techniques to perform 3-D imaging through walls in urban operations. Through-wall capabilities of interest include room mapping, imaging of in-wall structures, and detection of objects of interest. Such capabilities would greatly enhance situational awareness for military forces operating in the urban battle space. Current activities include hardware and software development and testing of an L-band through-wall SAR (TWSAR) system. Detection algorithms and automatic target recognition (ATR) systems are under investigation using experimental 2-D data. ATR may be more difficult in urban environments due to the high number of detectable objects and multi-path artifacts. Furthermore, penetrating through walls presents a formidable challenge as wall effects can greatly interfere with image quality inside buildings. By classifying wall material, wall compensation algorithms can be applied to enhance the image. In this paper, we present results from our preliminary investigation on detecting internal and external wall structures and their features (including doors and windows as well as internal wall construction) from scenes acquired with a single channel L-band TWSAR system. We evaluate the effectiveness of automatic detection based on the contourlet domain hidden Markov tree in the context of detecting wall edges and building features, while minimizing the amount of false edge detection. This work will form the basis of wall compensation algorithm development. The detection technique will also be used to detect objects of interests beyond walls once the SAR images have been wall compensated.
The arctic curve of the domain-wall six-vertex model in its anti-ferroelectric regime
Colomo, F; Zinn-Justin, P
2010-01-01
An explicit expression for the spatial curve separating the region of ferroelectric order (`frozen' zone) from the disordered one (`temperate' zone) in the six-vertex model with domain wall boundary conditions in its anti-ferroelectric regime is obtained.
Institute of Scientific and Technical Information of China (English)
Hongde Qin; Jing Shen; Xiaobo Chen
2011-01-01
The free-surface Green function method is widely used in solving the radiation or diffraction problems caused by a ship or ocean structure oscillating on the waves.In the context of inviscid potential flow,hydrodynamic problems such as multi-body interaction and tank side wall effect cannot be properly dealt with based on the traditional free-surface frequency domain Green function method,in which the water viscosity is omitted and the energy dissipation effect is absent.In this paper,an open-sea Green function with viscous dissipation was presented within the theory of visco-potential flow.Then the tank Green function with a partial reflection from the side walls in wave tanks was formulated as a formal sum of open-sea Green functions representing the infinite images between two parallel side walls of the source in the tank.The new far-field characteristics of the tank Green function is vitally important for improving the validity of side-wall effects evaluation,which can be used in supervising the tank model tests.
Qin, Hongde; Shen, Jing; Chen, Xiaobo
2011-09-01
The free-surface Green function method is widely used in solving the radiation or diffraction problems caused by a ship or ocean structure oscillating on the waves. In the context of inviscid potential flow, hydrodynamic problems such as multi-body interaction and tank side wall effect cannot be properly dealt with based on the traditional free-surface frequency domain Green function method, in which the water viscosity is omitted and the energy dissipation effect is absent. In this paper, an open-sea Green function with viscous dissipation was presented within the theory of visco-potential flow. Then the tank Green function with a partial reflection from the side walls in wave tanks was formulated as a formal sum of open-sea Green functions representing the infinite images between two parallel side walls of the source in the tank. The new far-field characteristics of the tank Green function is vitally important for improving the validity of side-wall effects evaluation, which can be used in supervising the tank model tests.
Direct observation of current-induced motion of a 3D vortex domain wall in cylindrical nanowires
Ivanov, Yurii P.
2017-05-08
The current-induced dynamics of 3D magnetic vortex domain walls in cylindrical Co/Ni nanowires are revealed experimentally using Lorentz microscopy and theoretically using micromagnetic simulations. We demonstrate that a spin-polarized electric current can control the reversible motion of 3D vortex domain walls, which travel with a velocity of a few hundred meters per second. This finding is a key step in establishing fast, high-density memory devices based on vertical arrays of cylindrical magnetic nanowires.
Spatio-temporal patterns in ultra-slow domain wall creep dynamics
Ferrero, Ezequiel E; Giamarchi, Thierry; Kolton, Alejandro B; Rosso, Alberto
2016-01-01
In presence of impurities, ferromagnetic and ferroelectric domain walls slide only above a finite external field. Close to this depinning threshold, the wall proceeds by large and abrupt jumps, called avalanches, while, at much smaller field, it creeps by thermal activation. In this work we develop a novel numerical technique that captures the ultra-slow creep regime over huge time scales. We point out the existence of activated events that involve collective reorganizations similar to avalanches, but, at variance with them, display correlated spatio-temporal patterns that resemble the complex sequence of aftershocks observed after a large earthquake. Remarkably, we show that events assembly in independent clusters owning the same scale-free statistics as critical depinning avalanches. This correlated dynamics should be experimentally accessible by magneto-optical imaging of ferro- magnetic films.
Transient and steady-state velocity of domain walls for a complete range of drive fields
Bourne, H. C., Jr.; Bartran, D. S.
1974-01-01
Approximate analytic solutions for transient and steady-state 180 deg domain wall motion in bulk magnetic material are obtained from the dynamic torque equations with a Gilbert damping term. The results for the Walker region in which the transient solution approaches the familiar Walker steady-state solution are presented in a slightly new form for completeness. An analytic solution corresponding to larger drive fields predicts an oscillatory motion with an average value which decreases with drive field for reasonable values of the damping parameter. These results agree with those obtained by a computer solution of the torque equation and those obtained with the assumption of a very large anisotropy field.
Algebraic arctic curves in the domain-wall six-vertex model
Colomo, F
2010-01-01
The arctic curve, i.e. the spatial curve separating ordered (or `frozen') and disordered (or `temperate) regions, of the six-vertex model with domain wall boundary conditions is discussed for the root-of-unity vertex weights. In these cases the curve is described by algebraic equations which can be worked out explicitly from the parametric solution for this curve. Some interesting examples are discussed in detail. The upper bound on the maximal degree of the equation in a generic root-of-unity case is obtained.
Impact of current on static and kinetic depinning fields of domain wall in ferromagnetic nanostrip
Indian Academy of Sciences (India)
R Arun; P Sabareesan; M Daniel
2015-11-01
The impact of current on static and kinetic depinning fields of a domain wall in a onedimensional ferromagnetic nanostrip is investigated analytically and numerically by solving the Landau–Lifshitz–Gilbert equation with adiabatic and non-adiabatic spin-transfer torques. The results show that in the absence of current, the static depinning field is greater than the kinetic depinning field. Both the depinning fields decrease by increasing the current applied in a direction opposite to the direction of the applied field. Both the depinning fields can also be tuned by the current to make them equal.
Domain Wall Junction in N=2 Supersymmetric QED in four dimensions
Kakimoto, K; Kakimoto, Kazuya; Sakai, Norisuke
2003-01-01
An exact solution of domain wall junction is obtained in N=2 supersymmetric (SUSY) QED with three massive hypermultiplets. The junction preserves two out of eight SUSY. Both a (magnetic) Fayet-Iliopoulos (FI) term and complex masses for hypermultiplets are needed to obtain the junction solution. There are zero modes corresponding to spontaneously broken translation, SUSY, and U(1). All broken and unbroken SUSY charges are explicitly worked out in the Wess-Zumino gauge in N=1 superfields as well as in components. The relation to models in five dimensions is also clarified.
Petit, Dorothée; Jausovec, Ana-Vanessa; Read, Dan; Cowburn, Russell P.
2008-06-01
The potential experienced by transverse domain walls (TDWs) in the vicinity of asymmetric constrictions or protrusions in thin Permalloy nanowires is probed using spatially resolved magneto-optical Kerr effect measurements. Both types of traps are found to act as pinning centers for DWs. The strength of pinning is found to depend on the trap type as well as on the chirality of the incoming DW; both types of traps are seen to act either as potential wells or potential barriers, also depending on the chirality of the DW. Micromagnetic simulations have been performed that are in good qualitative agreement with the experimental results.
Quark Contributions to Nucleon Momentum and Spin from Domain Wall fermion calculations
Energy Technology Data Exchange (ETDEWEB)
Syritsyn, Sergey N.; Green, Jeremy R. [MIT; Negele, John W. [MIT; Pochinsky, Andrew [MIT; Hagler, Philipp G. [Tech. U. Munich; Musch, Bernhard U. [Tech. U. Munich; Schroers, Wolfram
2011-12-01
We report contributions to the nucleon spin and momentum from light quarks calculated using dynamical domain wall fermions with pion masses down to 300 MeV and fine lattice spacing a=0.084 fm. Albeit without disconnected diagrams, we observe that spin and orbital angular momenta of both u and d quarks are opposite, almost canceling in the case of the d quark, which agrees with previous calculations using a mixed quark action. We also present the full momentum dependence of n=2 generalized form factors showing little variation with the pion mass.
Violation of chirality of the M\\"obius domain-wall Dirac operator from the eigenmodes
Cossu, Guido; Hashimoto, Shoji; Tomiya, Akio
2015-01-01
We investigate the effects of the violation of the Ginsparg-Wilson (GW) relation in the M\\"obius domain-wall fermion formulation on the lattice with finite fifth dimension. Using a decomposion in terms of the eigenmodes of its four-dimensional effective Dirac operator, we isolate the GW-violating terms for various physical quantities including the residual mass and the meson susceptibilities relevant for the effective restoration of the axial U(1) symmetry at finite temperature. Numerical result shows that the GW-violating effect is more significant, or even overwhelming, for the quantities that are dominated by the low-lying eigenmodes.
Charmonium current-current correlators with Mobius domain-wall fermion
Nakayama, Katsumasa; Hashimoto, Shoji
2015-01-01
We calculate the charmonium correlators on the lattice with $n_f = 2+ 1$ Moebius domain wall fermion, and extract the charm quark mass and the strong coupling constant. Time moments are defined by current-current correlators, which have been calculated in the continuum theory by perturbation theory. We extract the charm quark mass by matching the lattice results with the corresponding perturbative QCD calculations, using the recently generated ensembles by the JLQCD collaboration at lattice spacings $a = 0.083, 0.055$, and $0.044$ fm.
Decay constants and spectroscopy of mesons in lattice QCD using domain-wall fermions
Fahy, B; Hashimoto, S; Kaneko, T; Noaki, J; Tomii, M
2015-01-01
We report results of masses and decay constants of light and charmed pseudo-scalar mesons using lattice QCD with M\\"obius domain-wall fermions. Using this formulation we are able to compute pseudo-scalar decay constants through the pseudo-scalar density operator as well as with the axial-vector current. Results are shown from several lattice spacings and pion masses between 230 MeV and 500 MeV. We present an analysis of these results at different quark masses to show the chiral properties of the light mesons masses and decay constants.
Renormalization of domain-wall bilinear operators with short-distance current correlators
Tomii, M; Fahy, B; Fukaya, H; Hashimoto, S; Kaneko, T; Noaki, J
2016-01-01
We determine the renormalization constants for flavor non-singlet fermion bilinear operators of M\\"obius domain-wall fermions. The renormalization condition is imposed on the correlation functions in the coordinate space, such that the non-perturbative lattice calculation reproduces the perturbatively calculated counterpart at short distances. The perturbative expansion is precise as the coefficients are available up to $O(\\alpha_s^4)$. We employ $2+1$-flavor lattice ensembles at three lattice spacings in the range 0.044--0.080~fm.
Axial couplings of heavy hadrons from domain-wall lattice QCD
Detmold, William; Meinel, Stefan
2012-01-01
We calculate matrix elements of the axial current for static-light mesons and baryons in lattice QCD with dynamical domain wall fermions. We use partially quenched heavy hadron chiral perturbation theory in a finite volume to extract the axial couplings g_1, g_2, and g_3 from the data. These axial couplings allow the prediction of strong decay rates and enter chiral extrapolations of most lattice results in the b sector. Our calculations are performed with two lattice spacings and with pion masses down to 227 MeV.
Curvature Perturbation and Domain Wall Formation with Pseudo Scaling Scalar Dynamics
Ema, Yohei; Takimoto, Masahiro
2015-01-01
Cosmological dynamics of scalar field with a monomial potential $\\phi^{n}$ with a general background equation of state is revisited. It is known that if $n$ is smaller than a critical value, the scalar field exhibits a coherent oscillation and if $n$ is larger it obeys a scaling solution without oscillation. We study in detail the case where $n$ is equal to the critical value, and find a peculiar scalar dynamics which is neither oscillating nor scaling solution, and we call it a pseudo scaling solution. We also discuss cosmological implications of a pseudo scaling scalar dynamics, such as the curvature perturbation and the domain wall problem.
Inner products of Bethe states as partial domain wall partition functions
Kostov, Ivan
2012-01-01
We study the inner product of Bethe states in the inhomogeneous periodic XXX spin-1/2 chain of length L, which is given by the Slavnov determinant formula. We show that the inner product of an on-shell M-magnon state with a generic M-magnon state is given by the same expression as the inner product of a 2M-magnon state with a vacuum descendent. The second inner product is proportional to the partition function of the six-vertex model on a rectangular Lx2M grid, with partial domain-wall boundary conditions.
Status of nucleon structure calculations with 2+1 flavors of domain wall fermions
Lin, Meifeng
2013-01-01
We report the status of our nucleon structure calculations with 2+1 flavors of domain wall fermions on the RBC-UKQCD $32^3\\times64$ gauge ensembles with the Iwasaki+DSDR action. These ensembles have a fixed lattice scale of 1/a = 1.37 GeV, and two pion masses of about 170 and 250 MeV. Preliminary results for the isovector electromagnectic form factors and their corresponding root-mean-squared (r.m.s.) radii will be presented.
Non-perturbative renormalization of quark bilinear operators and B_K using domain wall fermions
Aoki, Y; Christ, N H; Dawson, C; Donnellan, M A; Izubuchi, T; Juttner, A; Li, S; Mawhinney, R D; Noaki, J; Sachrajda, Christopher T C; Soni, A; Tweedie, R J; Yamaguchi, A
2007-01-01
We present a calculation of the renormalization coefficients of the quark bilinear operators and the K-Kbar mixing parameter B_K. The coefficients relating the bare lattice operators to those in the RI/MOM scheme are computed non-perturbatively and then matched perturbatively to the MSbar scheme. The coefficients are calculated on the RBC/UKQCD 2+1 flavor dynamical lattice configurations. Specifically we use a 16^3 x 32 lattice volume, the Iwasaki gauge action at beta=2.13 and domain wall fermions with L_s=16.
Micromagnetic structure of the domain wall with Bloch lines in an electric field
Borich, M. A.; Tankeev, A. P.; Smagin, V. V.
2016-07-01
The micromagnetic structure of the domain wall (DW) with periodically distributed horizontal Bloch lines in a ferromagnetic film in an external electric field has been studied. The effect of the electric field on the internal DW micromagnetic structure is caused by inhomogeneous magnetoelectric coupling. Possible scenarios of the DW internal structure transformations implemented with varying the electric fields strength have been analyzed in detail. For each scenario, static characteristics of the system, such as the energy, DW profile, DW effective thickness, and electric polarization have been calculated.
Gerhardt, Theo; Drews, André; Meier, Guido
2012-01-18
We investigate switching and field-driven domain wall motion in nanowires with perpendicular magnetic anisotropy comprising local modifications of the material parameters. Intentional nucleation and pinning sites with various geometries inside the nanowires are realized via a local reduction of the anisotropy constant. Micromagnetic simulations and analytical calculations are employed to determine the switching fields and to characterize the pinning potentials and the depinning fields. Nucleation sites in the simulations cause a significant reduction of the switching field and are in excellent agreement with analytical calculations. Pinning potentials and depinning fields caused by the pinning sites strongly depend on their shapes and are well explained by analytical calculations.
Negative magnetoresistivity in holography
Sun, Ya-Wen
2016-01-01
Negative magnetoresistivity is a special magnetotransport property associated with chiral anomaly in four dimensional chiral anomalous systems, which refers to the transport behavior that the DC longitudinal magnetoresistivity decreases with increasing magnetic field. We calculate the longitudinal magnetoconductivity in the presence of backreactions of the magnetic field to gravity in holographic zero charge and axial charge density systems with and without axial charge dissipation. In the absence of axial charge dissipation, we find that the quantum critical conductivity grows with increasing magnetic field when the backreaction strength is larger than a critical value, in contrast to the monotonically decreasing behavior of quantum critical conductivity in the probe limit. With axial charge dissipation, we find the negative magnetoresistivity behavior. The DC longitudinal magnetoconductivity scales as $B$ in the large magnetic field limit, which deviates from the exact $B^2$ scaling of the probe limit resul...
Beguivin, A.; Petit, D. C. M. C.; Mansell, R.; Cowburn, R. P.
2017-01-01
Using Ga+ focussed ion beam irradiation of Ta/Pt/CoFeB/Pt perpendicularly magnetized nanowires, the nucleation and injection fields of domain walls into the nanowires is controlled. The nucleation and injection fields can be varied as a function of dose, however, the range of injection fields is found to be limited by the creation of a step in anisotropy between the irradiated and unirradiated regions. This can be altered by defocussing the beam, which allows the injection fields to be further reduced. The ability to define an arbitrary dose profile allows domain walls to be injected at different fields either side of an asymmetrically irradiated area, which could form the initial stage of a logic device. The effect of the thickness of the magnetic layer and the thickness of a Ta underlayer on the dose required to remove the perpendicular anisotropy is also studied and is seen that for similar Ta underlayers the dose is determined by the thickness of the magnetic layer rather than its anisotropy. This finding is supported by some transport of ions in matter simulations.
Artificial chemical and magnetic structure at the domain walls of an epitaxial oxide
Noheda, Beatriz
Progress in nanotechnology requires new paradigms for materials synthesis that allow controlling their functionality down to the smallest scales. Here we report a novel two-dimensional ferromagnetic phase that is synthesized at the domain walls (DWs) of the antiferromagnetic insulator TbMnO3 when grown in thin layers under epitaxial strain. This Mn oxide phase presents an atomic arrangement that does not exist in bulk and cannot be synthesized by standard chemical routes. The number of 2D ferromagnetic sheets can be controlled by tuning the thickness of the thin films, giving rise to volume fractions that go up to 25% of the total film volume. Such novel phases are driven by a unique environment induced by the symmetry breaking and large stresses present at domain walls, which function as nanoreactors. This new class of nanoscale materials may find innovative applications in nanoelectronics and spintronics. The work is published as S. Farokhipoor, C. Magén, S. Venkatesan, J. Íñiguez, C. J. M. Daumont, D. Rubi, E. Snoeck, M. Mostovoy, C. de Graaf, A. Müller, M. Döblinger, C. Scheu, B. Noheda, Nature 515, 379 (2014)
Steady motion of skyrmions and domains walls under diffusive spin torques
Elías, Ricardo Gabriel
2017-03-09
We explore the role of the spin diffusion of conducting electrons in two-dimensional magnetic textures (domain walls and skyrmions) with spatial variation of the order of the spin precession length λex. The effect of diffusion reflects in four additional torques that are third order in spatial derivatives of magnetization and bilinear in λex and in the nonadiabatic parameter β′. In order to study the dynamics of the solitons when these diffusive torques are present, we derive the Thiele equation in the limit of steady motion and we compare the results with the nondiffusive limit. When considering a homogenous current these torques increase the longitudinal velocity of transverse domain walls of width Δ by a factor (λex/Δ)2(α/3), α being the magnetic damping constant. In the case of single skyrmions with core radius r0 these new contributions tend to increase the Magnus effect in an amount proportional to (λex/r0)2(1+2αβ′).
Phase Competition, Solitons, and Domain Walls in Neutral–Ionic Transition Systems
Tsuchiizu, Masahisa; Yoshioka, Hideo; Seo, Hitoshi
2016-10-01
Phase competition and excitations in the one-dimensional neutral-ionic transition systems are theoretically studied comprehensively. From the semiclassical treatment of the bosonized Hamiltonian, we examine the competition among the neutral (N), ferroelectric-ionic (I$_\\mathrm{ferro}$) and paraelectric-ionic (I$_\\mathrm{para}$) states. The phase transitions between them can become first-order when the fluctuation-induced higher-order commensurability potential is considered. In particular, the description of the first-order phase boundary between N and I$_\\mathrm{ferro}$ enables us to analyze N-I$_\\mathrm{ferro}$ domain walls. Soliton excitations in the three phases are described explicitly and their formation energies are evaluated across the phase boundaries. The characters of the soliton and domain-wall excitations are classified in terms of the topological charge and spin. The relevance to the experimental observations in the molecular neutral-ionic transition systems is discussed. We ascribe the pressure-induced crossover in tetrathiafulvalene-$p$-chloranil (TTF-CA) at a high-temperature region to that from the N to the I$_\\mathrm{para}$ state, and discuss its consequence.
Energy Technology Data Exchange (ETDEWEB)
Graham, Joseph T. [Nuclear Engineering Teaching Laboratory, University of Texas at Austin, Austin, Texas 78758 (United States); Electronic, Optic and Nano Materials Department, Sandia National Laboratories, Albuquerque, New Mexico 87185 (United States); Brennecka, Geoff L.; Ihlefeld, Jon F. [Electronic, Optic and Nano Materials Department, Sandia National Laboratories, Albuquerque, New Mexico 87185 (United States); Ferreira, Paulo [Materials Science and Engineering Program, University of Texas at Austin, Austin, Texas 78751 (United States); Small, Leo [Electronic, Optic and Nano Materials Department, Sandia National Laboratories, Albuquerque, New Mexico 87185 (United States); Department of Materials Science and Engineering, Rensselaer Polytechnic Institute, Troy, New York 12180 (United States); Duquette, David [Department of Materials Science and Engineering, Rensselaer Polytechnic Institute, Troy, New York 12180 (United States); Apblett, Christopher [Advanced Power Sources R and D Department, Sandia National Laboratories, Albuquerque, New Mexico 87185 (United States); Landsberger, Sheldon [Nuclear Engineering Teaching Laboratory, University of Texas at Austin, Austin, Texas 78758 (United States)
2013-03-28
The effects of neutron-induced damage on the ferroelectric properties of thin film lead zirconate titanate (PZT) were investigated. Two sets of PbZr{sub 0.52}Ti{sub 0.48}O{sub 3} films of varying initial quality were irradiated in a research nuclear reactor up to a maximum 1 MeV equivalent neutron fluence of (5.16 {+-} 0.03) Multiplication-Sign 10{sup 15} cm{sup -2}. Changes in domain wall mobility and reversibility were characterized by polarization-electric field measurements, Rayleigh analysis, and analysis of first order reversal curves (FORC). With increasing fluence, extrinsic contributions to the small-signal permittivity diminished. Additionally, redistribution of irreversible hysterons towards higher coercive fields was observed accompanied by the formation of a secondary hysteron peak following exposure to high fluence levels. The changes are attributed to the radiation-induced formation of defect dipoles and other charged defects, which serve as effective domain wall pinning sites. Differences in damage accumulation rates with initial film quality were observed between the film sets suggesting a dominance of pre-irradiation microstructure on changes in macroscopic switching behavior.
Energy Technology Data Exchange (ETDEWEB)
Serena, P. A. [Instituto de Ciencias de Materiales de Madrid, Madrid (Spain); Costa-Kraemer, J. L. [Instituto de Microelectronica de Madrid, Madrid (Spain)
2001-03-01
A Monte Carlo algorithm suitable to study systems described by an anisotropic Heisenberg Hamiltonian is presented. This technique has been tested successfully with 3D and 2D systems, illustrating how magnetic properties depend on the dimensionality and the coordination number. We have found that magnetic properties of constrictions differ from those appearing in bulk. In particular, spin fluctuations are considerable larger than those calculated for bulk materials. In addition, domain walls are strongly modified when a constriction is present, with a decrease of the domain-wall width. This decrease is explained in terms of previous theoretical works. [Spanish] Se presenta un algoritmo de Monte Carlo para estudiar sistemas discritos por un hamiltoniano anisotropico de Heisenburg. Esta tecnica ha sido probada exitosamente con sistemas de dos y tres dimensiones, ilustrado con las propiedades magneticas dependen de la dimensionalidad y el numero de coordinacion. Hemos encontrado que las propiedades magneticas de constricciones difieren de aquellas del bulto. En particular, las fluctuaciones de espin son considerablemente mayores. Ademas, las paredes de dominio son fuertemente modificadas cuando una construccion esta presente, originando un decrecimiento del ancho de la pared de dominio. Damos cuenta de este decrecimiento en terminos de un trabajo teorico previo.
Magnetic domain-wall motion twisted by nanoscale probe-induced spin transfer
Wang, J.; Xie, L. S.; Wang, C. S.; Zhang, H. Z.; Shu, L.; Bai, J.; Chai, Y. S.; Zhao, X.; Nie, J. C.; Cao, C. B.; Gu, C. Z.; Xiong, C. M.; Sun, Y.; Shi, J.; Salahuddin, S.; Xia, K.; Nan, C. W.; Zhang, J. X.
2014-12-01
A method for deterministic control of magnetism using an electrical stimulus is highly desired for the new generation of magnetoelectronic devices. Much effort has been focused on magnetic domain-wall (DW) motion manipulated by a successive injection of spin-polarized current into a magnetic nanostructure. However, an integrant high-threshold current density of 1011˜1012A /m2 inhibits the integration with low-energy-cost technology. Here, we report an approach to manipulate a single magnetic domain wall with a perpendicular anisotropy in a manganite/dielectric/metal capacitor using a probe-induced spin displacement. A spin-transfer torque (STT) occurs in the strongly correlated manganite film during the spin injection into the capacitor from the nanoscale magnetized tip with an ultralow voltage of 0.1 V, where a lower bound of the estimated threshold spin-polarized current density is ˜108A /m2 at the tip/manganite interface. The dynamic of DW motions are analyzed using the Landau-Lifshitz-Gilbert method. This probe-voltage-controlled DW motion, at an ambient condition, demonstrates a critical framework for the fundamental understanding of the manipulation of the nanomagnet systems with low-energy consumption.
Effect of Joule heating in current-driven domain wall motion
Yamaguchi, A.; Nasu, S.; Tanigawa, H.; Ono, T.; Miyake, K.; Mibu, K.; Shinjo, T.
2005-01-01
It was found that high current density needed for the current-driven domain wall motion results in the Joule heating of the sample. The sample temperature, when the current-driven domain wall motion occurred, was estimated by measuring the sample resistance during the application of a pulsed current. The sample temperature was 750 K for the threshold current density of 6.7×1011A/m2 in a 10-nm-thick Ni81Fe19 wire with a width of 240 nm on thermally oxidized silicon substrate. The temperature was raised to 830 K for the current density of 7.5×1011A/m2, which is very close to the Curie temperature of bulk Ni81Fe19. When the current density exceeded 7.5×1011A/m2, an appearance of a multidomain structure in the wire was observed by magnetic force microscopy, suggesting that the sample temperature exceeded the Curie temperature.
PRGL:A cell wall proline-rich protein containning GASA domain in Gerbera hybrida
Institute of Scientific and Technical Information of China (English)
2008-01-01
PRPs (proline-rich proteins) are a group of cell wall proteins characterized by their proline and hy- droproline-rich repetitive peptides. The expression of PRPs in plants is stimulated by wounding and environmental stress. GASA (gibberellic acid stimulated in Arabidopsis) proteins are small peptides sharing a 60 amino acid conserved C-terminal domain containing twelve invariant cysteine residues. Most of GASAs reported are localized to apoplasm or cell wall and their expression was regulated by gibberellins (GAs). It has been reported that, in French bean, these two proteins encoding by two distinct genes formed a two-component chitin-receptor involved in plant-pathogen interactions when plant was infected. We cloned a full-length cDNA of PRGL (proline-rich GASA-like) gene which encodes a protein containing both PRP and GASA-like domains. It is demonstrated that PRGL is a new protein with characteristics of PRP and GASA by analyzing its protein structure and gene expression.
Magnetic fingerprint of interfacial coupling between CoFe and nanoscale ferroelectric domain walls
Zhang, Qintong; Murray, Peyton; You, Lu; Wan, Caihua; Zhang, Xuan; Li, Wenjing; Khan, Usman; Wang, Junling; Liu, Kai; Han, Xiufeng
2016-08-01
Magnetoelectric coupling in ferromagnetic/multiferroic systems is often manifested in the exchange bias effect, which may have combined contributions from multiple sources, such as domain walls, chemical defects, or strain. In this study we magnetically "fingerprint" the coupling behavior of CoFe grown on epitaxial BiFeO3 (BFO) thin films by magnetometry and the first-order-reversal-curves (FORC). The contribution to exchange bias from 71°, 109° and charged ferroelectric domain walls (DWs) was elucidated by the FORC distribution. CoFe samples grown on BFO with 71° DWs only exhibit an enhancement of the coercivity, but little exchange bias. Samples grown on BFO with 109° DWs and mosaic DWs exhibit a much larger exchange bias, with the main enhancement attributed to 109° and charged DWs. Based on the Malozemoff random field model, a varying-anisotropy model is proposed to account for the exchange bias enhancement. This work sheds light on the relationship between the exchange bias effect of the CoFe/BFO heterointerface and the ferroelectric DWs, and provides a path for multiferroic device analysis and design.
A construction of the Schr\\"odinger Functional for M\\"obius Domain Wall Fermions
Murakami, Yuko
2014-01-01
We construct the Schr\\"odinger Functional (SF) setup for the M\\"obius domain wall fermions (MDWF). The method is an extension of the method proposed by Takeda for the standard domain wall fermion. In order to fulfill the requirement that the lattice Dirac operator with the SF boundary obeys the L\\"uscher's universality argument: the lattice chiral fermion with the SF boundary condition breaks the chiral symmetry at the temporal boundary, we impose the parity symmetry with respect to the fifth-direction on the MDWF operator. This additional symmetry restricts the choice of the parameter of the MDWF so that the optimal parameter from the Zolotarev optimal approximation cannot be applied. We introduce a modified parameter set having the fifth-dimensional parity symmetry. We investigate the MDWF with the SF boundary by observing eigenvalues of the Hermitian operator and the Ginsparg-Wilson relation violation at the tree-level. We compare the computational cost with that of the standard DWF with the SF scheme.
Molecular anisotropic magnetoresistance
Otte, Fabian; Heinze, Stefan; Mokrousov, Yuriy
2015-12-01
Using density functional theory calculations, we demonstrate that the effect of anisotropic magnetoresistance (AMR) can be enhanced by orders of magnitude with respect to conventional bulk ferromagnets in junctions containing molecules sandwiched between ferromagnetic leads. We study ballistic transport in metal-benzene complexes contacted by 3 d transition-metal wires. We show that a gigantic AMR can arise from spin-orbit coupling effects in the leads, drastically enhanced by orbital-symmetry filtering properties of the molecules. We further discuss how this molecular anisotropic magnetoresistance (MAMR) can be tuned by the proper choice of materials and their electronic properties.
Nagatani, Y
2001-01-01
We show that a spherical electroweak domain wall is formed around a small black hole and this is a general property of the Hawking radiation in the vacuum of the Standard Model. The wall appears not only for the first order phase transition in the electroweak theory but also for the second order one because the black hole heats up its neighborhood locally by the Hawking radiation in any case. We propose a model for unifying the origin of the baryon number and the cold dark matter in our universe by using properties of the primordial black hole with a mass of several hundred kilograms. The interaction between our wall and the Hawking-radiated-particles can create a baryon number which is proportional to the mass of the black hole as well as the CP broken phase in the extension of the Standard Model. Our model can explain both the baryon-entropy ratio B/S \\sim 10^{-10} and the energy density of the dark matter, provided that the following three conditions are satisfied: (i) the primordial black holes dominate i...
Li, Mei; Wang, Jianbo; Lu, Jie
2017-02-01
The statics and field-driven dynamics of transverse domain walls (TDWs) in magnetic nanowires (NWs) have attracted continuous interests because of their theoretical significance and application potential in future magnetic logic and memory devices. Recent results demonstrate that uniform transverse magnetic fields (TMFs) can greatly enhance the wall velocity, meantime leave a twisting in the TDW azimuthal distribution. For application in high-density NW devices, it is preferable to erase the twisting so as to minimize magnetization frustrations. Here we report the realization of a completely planar TDW with arbitrary tilting attitude in a magnetic biaxial NW under a TMF pulse with fixed strength and well-designed orientation profile. We smooth any twisting in the TDW azimuthal plane thus completely decouple the polar and azimuthal degrees of freedom. The analytical differential equation describing the polar angle distribution is derived and the resulting solution is not the Walker-ansatz form. With this TMF pulse comoving, the field-driven dynamics of the planar TDW is investigated with the help of the asymptotic expansion method. It turns out the comoving TMF pulse increases the wall velocity under the same axial driving field. These results will help to design a series of modern magnetic devices based on planar TDWs.
Anisotropic electrical resistance in mesoscopic LaAlO3/SrTiO3 devices with individual domain walls.
Goble, Nicholas J; Akrobetu, Richard; Zaid, Hicham; Sucharitakul, Sukrit; Berger, Marie-Hélène; Sehirlioglu, Alp; Gao, Xuan P A
2017-03-15
The crystal structure of bulk SrTiO3(STO) transitions from cubic to tetragonal at around 105 K. Recent local scanning probe measurements of LaAlO3/SrTiO3 (LAO/STO) interfaces indicated the existence of spatially inhomogeneous electrical current paths and electrostatic potential associated with the structural domain formation in the tetragonal phase of STO. Here we report a study of temperature dependent electronic transport in combination with the polarized light microscopy of structural domains in mesoscopic LAO/STO devices. By reducing the size of the conductive interface to be comparable to that of a single tetragonal domain of STO, the anisotropy of interfacial electron conduction in relationship to the domain wall and its direction was characterized between T = 10-300 K. It was found that the four-point resistance measured with current parallel to the domain wall is larger than the resistance measured perpendicular to the domain wall. This observation is qualitatively consistent with the current diverting effect from a more conductive domain wall within the sample. Among all the samples studied, the maximum resistance ratio found is at least 10 and could be as large as 10(5) at T = 10 K. This electronic anisotropy may have implications on other oxide hetero-interfaces and the further understanding of electronic/magnetic phenomena found in LAO/STO.
Anisotropic electrical resistance in mesoscopic LaAlO3/SrTiO3 devices with individual domain walls
Goble, Nicholas J.; Akrobetu, Richard; Zaid, Hicham; Sucharitakul, Sukrit; Berger, Marie-Hélène; Sehirlioglu, Alp; Gao, Xuan P. A.
2017-01-01
The crystal structure of bulk SrTiO3(STO) transitions from cubic to tetragonal at around 105 K. Recent local scanning probe measurements of LaAlO3/SrTiO3 (LAO/STO) interfaces indicated the existence of spatially inhomogeneous electrical current paths and electrostatic potential associated with the structural domain formation in the tetragonal phase of STO. Here we report a study of temperature dependent electronic transport in combination with the polarized light microscopy of structural domains in mesoscopic LAO/STO devices. By reducing the size of the conductive interface to be comparable to that of a single tetragonal domain of STO, the anisotropy of interfacial electron conduction in relationship to the domain wall and its direction was characterized between T = 10–300 K. It was found that the four-point resistance measured with current parallel to the domain wall is larger than the resistance measured perpendicular to the domain wall. This observation is qualitatively consistent with the current diverting effect from a more conductive domain wall within the sample. Among all the samples studied, the maximum resistance ratio found is at least 10 and could be as large as 105 at T = 10 K. This electronic anisotropy may have implications on other oxide hetero-interfaces and the further understanding of electronic/magnetic phenomena found in LAO/STO. PMID:28295058
Directory of Open Access Journals (Sweden)
Eduardo Martinez
2012-01-01
Full Text Available The current-induced domain wall motion along thin ferromagnetic strips with high perpendicular magnetocrystalline anisotropy is studied by means of full micromagnetic simulations and the extended one-dimensional model, taking into account thermal effects and edge roughness. A slow creep regime, where the motion is controlled by wall pinning and thermal activation, and a flow regime with linear variation of the DW velocity, are observed. In asymmetric stacks, where the Rashba spin-orbit field stabilizes the domain wall against turbulent transformations, the steady linear regime is extended to higher currents, leading to higher velocities than in single-layer or symmetric stacks. The pinning and depinning at and from a local constriction were also studied. The results indicate that engineering pinning sites in these strips provide an efficient pathway to achieve both high stability against thermal fluctuations and low-current depinning avoiding Joule heating. Finally, the current-driven dynamics of a pinned domain wall is examined, and both the direct and the alternating contributions to the induced voltage signal induced are characterized. It was confirmed that the direct contribution to the voltage signal can be linearly enhanced with the number of pinned walls, an observation which could be useful to develop domain-wall-based nano-oscillators.
Bang, Do
2016-05-23
We investigate the current-induced domain wall motion in perpendicular magnetized Tb/Co wires with structure inversion asymmetry and different layered structures. We find that the critical current density to drive domain wall motion strongly depends on the layered structure. The lowest critical current density ∼15MA/cm2 and the highest slope of domain wall velocity curve are obtained for the wire having thin Co sublayers and more inner Tb/Co interfaces, while the largest critical current density ∼26MA/cm2 required to drive domain walls is observed in the Tb-Co alloy magnetic wire. It is found that the Co/Tb interface contributes negligibly to Dzyaloshinskii-Moriya interaction, while the effective spin-orbit torque strongly depends on the number of Tb/Co inner interfaces (n). An enhancement of the antidamping torques by extrinsic spin Hall effect due to Tb rare-earth impurity-induced skew scattering is suggested to explain the high efficiency of current-induced domain wall motion.
Influence of Domain Wall on Magnetocaloric Effect in GdPt$_{2}$
2006-01-01
The resistivity, magnetoresistance and in-field heat capacity measurements were performed on GdPt$_{2}$ intermetallic compound. The magnetocaloric parameters $\\Delta T_{ad}$ and $-\\Delta S$ were derived from the in-field heat capacity data. Comparison has been made between the magnetocaloric effect $-\\Delta S$ and difference in resistivity $-\\Delta \\rho$ $(=\\rho(H)-\\rho(0))$ as a function of temperature. There is distinct difference in the temperature dependence of $-\\Delta S$ and $-\\Delta \\r...
Energy Technology Data Exchange (ETDEWEB)
Xu, Qingping; Mengin-Lecreulx, Dominique; Liu, Xueqian W.; Patin, Delphine; Farr, Carol L.; Grant, Joanna C.; Chiu, Hsiu-Ju; Jaroszewski, Lukasz; Knuth, Mark W.; Godzik, Adam; Lesley, Scott A.; Elsliger, Marc-André; Deacon, Ashley M.; Wilson, Ian A.
2015-09-15
Bacterial SH3 (SH3b) domains are commonly fused with papain-like Nlp/P60 cell wall hydrolase domains. To understand how the modular architecture of SH3b and NlpC/P60 affects the activity of the catalytic domain, three putative NlpC/P60 cell wall hydrolases were biochemically and structurally characterized. These enzymes all have γ-
Wang, Hua
2016-01-01
Low-dimensional multiferroic materials hold great promises in miniaturized device applications such as nanoscale transducers, actuators, sensors, photovoltaics, and nonvolatile memories. Here, using first-principles theory we predict that two-dimensional (2D) monolayer Group IV monochalcogenides including GeS, GeSe, SnS, and SnSe are a class of 2D semiconducting multiferroics with strongly coupled giant in-plane spontaneous ferroelectric polarization and spontaneous ferroelastic lattice strain that are thermodynamically stable at room temperature and beyond, and can be effectively modulated by elastic strain engineering. Their optical absorption spectra exhibit strong in-plane anisotropy with visible-spectrum excitonic gaps and sizable exciton binding energies, rendering the unique characteristics of low-dimensional semiconductors. More importantly, the predicted low domain wall energy and small migration barrier together with the coupled multiferroic order and anisotropic electronic structures suggest their ...
Study of the conformal region of the SU(3) gauge theory with domain-wall fermions
Noaki, J; Ishikawa, K-I; Iwasaki, Y; Yoshie, T
2015-01-01
We investigate the phase structure of the SU(3) gauge theory with $N_f=8$ by numerical simulations employing the massless Domain-Wall fermions.Our aim is to study directly the massless quark region, since it is the most important region to clarify the properties of conformal theories. When the number of flavor is within the conformal window, it is claimed recently with Wilson quarks that there is the conformal region at the small quark mass region in the parameter space in addition to the confining phase and the deconfining phase. We study the properties of the conformal region investing the spatial Polyakov loops and the temporal meson propagators. Our data imply that there is the conformal region, and a phase transition between the confining phase and the conformal region takes place. These results are consistent with the claim that the conformal window is between $7$ and $16$. Progress reports on other related studies are also presented.
Mesoscopic Metal-Insulator Transition at Ferroelastic Domain Walls in VO2
Energy Technology Data Exchange (ETDEWEB)
Jones, Keith M [ORNL; Kalinin, Sergei V [ORNL; Kolmakov, Andrei [ORNL; Luk' yanchuk, Prof. Igor A. [University of Picardie Jules Verne, Amiens, France; Meunier, Vincent [ORNL; Proksch, Roger [Asylum Research, Santa Barbara, CA; Shelton Jr, William Allison [ORNL; Strelcov, Evgheni [Southern Illinois University; Tselev, Alexander [ORNL
2010-01-01
The novel phenomena induced by symmetry breaking at homointerfaces between ferroic variants in ferroelectric and ferroelastic materials have attracted recently much attention. Using variable temperature scanning microwave microscopy, we demonstrate the mesoscopic strain-induced metal-insulator phase transitions in the vicinity of ferroelastic domain walls in the semiconductive VO2 that nucleated at temperatures as much as 10-12 C below bulk transition, resulting in the formation of conductive channels in the material. Density functional theory is used to rationalize the process low activation energy. This behavior, linked to the strain inhomogeneity inherent in ferroelastic materials, can strongly affect interpretation of phase-transition studies in VO2 and similar materials with symmetry-lowering transitions, and can also be used to enable new generations of electronic devices though strain engineering of conductive and semiconductive regions.
Geometrically pinned magnetic domain wall for multi-bit per cell storage memory
Bahri, M. Al; Sbiaa, R.
2016-06-01
Spintronic devices currently rely on magnetic switching or controlled motion of domain walls (DWs) by an external magnetic field or a spin-polarized current. Controlling the position of DW is essential for defining the state/information in a magnetic memory. During the process of nanowire fabrication, creating an off-set of two parts of the device could help to pin DW at a precise position. Micromagnetic simulation conducted on in-plane magnetic anisotropy materials shows the effectiveness of the proposed design for pinning DW at the nanoconstriction region. The critical current for moving DW from one state to the other is strongly dependent on nanoconstricted region (width and length) and the magnetic properties of the material. The DW speed which is essential for fast writing of the data could reach values in the range of hundreds m/s. Furthermore, evidence of multi-bit per cell memory is demonstrated via a magnetic nanowire with more than one constriction.
Easy moment direction and antiferromagnetic domain wall motion in Mn2Au
Barthem, Vitoria M. T. S.; Colin, Claire V.; Haettel, Richard; Dufeu, Didier; Givord, Dominique
2016-05-01
The interest of giving active functions to antiferromagnetic (AFM) materials in spintronics devices has been realized recently. Mn2Au is a high-Néel temperature antiferromagnet with large Mn moment, lying in plane of the tetragonal structure. To determine the direction of the moments in Mn2Au, an original approach is demonstrated, which should be generic to planar AFM materials. It involves the rotation of the granular sample around an axis perpendicular to the applied magnetic field. The family of easy moment directions is . For grains prevented from rotating, the dominant magnetization process is AFM domain wall motion. Textured Mn2Au nanoelements could be introduced in spintronics devices, in which the Mn moments would be switched under modest external excitation.
Miniature Hall sensor integrated on a magnetic thin film for detecting domain wall motion
Kubota, M.; Tokunaga, Y.; Kanazawa, N.; Kagawa, F.; Tokura, Y.; Kawasaki, M.
2013-08-01
We have fabricated a cross-bar Hall sensor made of 50-nm-wide and 100-nm-thick bismuth wires patterned by an electron-beam lithography and lift-off. The Hall coefficient at 300 K is as large as -0.44 cm3/C, yielding in a high product sensitivity of about 5 V/(A T). The series resistance was reduced as low as 1.7 kΩ with a short bar configuration, resulting in a high signal-to-noise ratio of 38.5 dB. These characteristics are far better than those reported with similar dimensions. The Hall element was successfully demonstrated for detecting the domain wall motion in an iron garnet film employed as the substrate.
Energy Technology Data Exchange (ETDEWEB)
Seifert, C.
2006-09-14
The gold-induced (5 x 2)-reconstruction on the Si(111) surface has been investigated in detail. Investigations with scanning tunneling microscopy, electron diffraction and simple electron diffraction simulation as combining element are presented. The defect density in the (5 x 2)-reconstructed areas has been analysed in dependency on temperature and gold density on the surface. One important result is the categorization of this reconstruction as domain-wall reconstruction like the other gold induced reconstructions on this surface in the submonolayer-coverage regime. The correlation of the adatoms on the (5 x 2)-reconstructed areas is analysed and the silicon coverage in the areas is determined from the growth dynamics of the reconstruction. Based on this, a new model, which has been developed in cooperation with Steve Erwin from the Naval Research Center, Washington, is presented. (orig.)
Breitkreutz, Stephan; Fischer, Andreas; Kaffah, Silmi; Weigl, Stephanie; Eichwald, Irina; Ziemys, Grazvydas; Schmitt-Landsiedel, Doris; Becherer, Markus
2015-05-01
In this paper, the domain wall (DW) nucleation time and the DW nucleation probability of field-coupled magnets with perpendicular magnetic anisotropy are measured by experiment. A well-established Arrhenius model based on thermally activated magnetization reversal is applied to describe the time-dependent DW nucleation probability. Magneto-optical microscopy(MOKE) is used in the experiments to determine the DW nucleation time and the DW nucleation probability in a pNML inverter structure. The DW propagation speed is measured in order to calculate the required DW propagation time for entire magnetization reversal of pNML logic gates. Experimental results are compared to the derived model. Our results show that the interaction in pNML logic gates plays a significant role for the time-dependent DW nucleation probability and therefore for the reliability of field-coupled circuits.
Neutral B meson mixing with static heavy and domain-wall light quarks
Ishikawa, Tomomi; Izubuchi, Taku; Lehner, Christoph; Soni, Amarjit
2013-01-01
Neutral B meson mixing matrix elements and B meson decay constants are calculated. Static approximation is used for b quark and domain-wall fermion formalism is employed for light quarks. The calculations are done on 2+1 flavor dynamical ensembles, whose lattice spacings are 0.086 fm and 0.11 fm with a fixed physical spatial volume of about (2.7 fm)^3. In the static quark action, link-smearings are used to improve the signal-to-noise ratio. We employ two kinds of link-smearings and their results are combined in taking a continuum limit. For the matching between the lattice and the continuum theory, one-loop perturbative calculations are used including O(a) improvements to reduce discretization errors. We obtain SU(3) braking ratio \\xi=1.222(60) in the static limit of b quark.
Ring-shaped Racetrack memory based on spin orbit torque driven chiral domain wall motions
Zhang, Yue; Zhang, Xueying; Hu, Jingtong; Nan, Jiang; Zheng, Zhenyi; Zhang, Zhizhong; Zhang, Youguang; Vernier, Nicolas; Ravelosona, Dafine; Zhao, Weisheng
2016-10-01
Racetrack memory (RM) has sparked enormous interest thanks to its outstanding potential for low-power, high-density and high-speed data storage. However, since it requires bi-directional domain wall (DW) shifting process for outputting data, the mainstream stripe-shaped concept certainly suffers from the data overflow issue. This geometrical restriction leads to increasing complexity of peripheral circuits or programming as well as undesirable reliability issue. In this work, we propose and study ring-shaped RM, which is based on an alternative mechanism, spin orbit torque (SOT) driven chiral DW motions. Micromagnetic simulations have been carried out to validate its functionality and exhibit its performance advantages. The current flowing through the heavy metal instead of ferromagnetic layer realizes the “end to end” circulation of storage data, which remains all the data in the device even if they are shifted. It blazes a promising path for application of RM in practical memory and logic.
Low-Scale Leptogenesis and the Domain Wall Problem in Models with Discrete Flavor Symmetries
Riva, Francesco
2010-01-01
We propose a new mechanism for leptogenesis, which is naturally realized in some models with a flavor symmetry based on the discrete group A_4, where the symmetry breaking parameter also controls the Majorana masses for the heavy right handed (RH) neutrinos. During the early universe, for T>TeV, part of the symmetry is restored, due to finite temperature contributions, and the RH neutrinos remain massless and can be produced in thermal equilibrium even at temperatures well below the most conservative gravitino bounds. Below this temperature the phase transition occurs and they become massive, decaying out of equilibrium and producing the necessary lepton asymmetry. Unless the symmetry is broken explicitly by Planck-suppressed terms, the domain walls generated by the symmetry breaking survive till the quark-hadron phase transition, where they disappear due to a small energy splitting between different vacua caused by the QCD anomaly.
fK /f{pi} in Full QCD with Domain Wall Valence Quarks
Energy Technology Data Exchange (ETDEWEB)
Silas Beane; Paulo Bedaque; Konstantinos Orginos; Martin Savage
2007-05-01
We compute the ratio of pseudoscalar decay constants f{sub K}/f{sub {pi}} using domain-wall valence quarks and rooted improved Kogut-Susskind sea quarks. By employing continuum chiral perturbation theory, we extract the Gasser-Leutwyler low-energy constant L{sub 5}, and extrapolate f{sub K}/f{sub {pi}} to the physical point. We find: f{sub K}/f{sub {pi}} = 1.218 {+-} 0.002{sub -0.024}{sup +0.011} where the first error is statistical and the second error is an estimate of the systematic due to chiral extrapolation and fitting procedures. This value agrees within the uncertainties with the determination by the MILC collaboration, calculated using Kogut-Susskind valence quarks, indicating that systematic errors arising from the choice of lattice valence quark are small.
Spin-Transfer-Torque-Assisted Domain-Wall Creep in a Co/Pt Multilayer Wire
San Emeterio Alvarez, L.; Wang, K.-Y.; Lepadatu, S.; Landi, S.; Bending, S. J.; Marrows, C. H.
2010-04-01
We have studied field- and current-driven domain-wall (DW) creep motion in a perpendicularly magnetized Co/Pt multilayer wire by real-time Kerr microscopy. The application of a dc current of density of ≲107A/cm2 assisted only the DW creeping under field in the same direction as the electron flow, a signature of spin-transfer torque effects. We develop a model dealing with both bidirectional spin-transfer effects and Joule heating, with the same dynamical exponent μ=1/4 for both field- and current-driven creep, and use it to quantify the spin-transfer efficiency as 3.6±0.6Oecm2/MA in our wires, confirming the significant nonadiabatic contribution to the spin torque.
Effects of domain walls in quantum anomalous Hall insulator/superconductor heterostructures
Chen, Chui-Zhen; He, James Jun; Xu, Dong-Hui; Law, K. T.
2017-07-01
In a recent experiment, half-quantized longitudinal conductance plateaus (HQCPs) of height e/22 h have been observed in quantum anomalous Hall (QAH) insulator/superconductor heterostructure transport measurements. However, there are debates about whether these HQCPs are caused by Majorana edge modes or other trivial reasons. It was predicted that HQCPs can only appear when the Hall conductance σx y is quantized. Surprisingly, HQCPs appear when the Hall conductance σx y is only 80% of the quantized value at which extra conducting channels in the bulk should ruin the HQCPs. In this Rapid Communication, we explain how domain walls can cause σx y to deviate from its quantized value and at the same time maintain the quantization of HQCPs. Importantly, our study also explains a long standing puzzle of why ρx x can be finite when ρx y is quantized in QAH systems.
Zhuo, Fengjun; Sun, Z. Z.
2016-01-01
Field-driven domain wall (DW) motion in ferromagnetic nanowires with easy- and hard-axis anisotropies was studied theoretically and numerically in the presence of the bulk Dzyaloshinskii-Moriya interaction (DMI) based on the Landau-Lifshitz-Gilbert equation. We propose a new trial function and offer an exact solution for DW motion along a uniaxial nanowire driven by an external magnetic field. A new strategy was suggested to speed up DW motion in a uniaxial magnetic nanowire with large DMI parameters. In the presence of hard-axis anisotropy, we find that the breakdown field and velocity of DW motion was strongly affected by the strength and sign of the DMI parameter under external fields. This work may be useful for future magnetic information storage devices based on DW motion. PMID:27118064
Stabilizing and controlling domain walls and dark-ring cavity solitons.
Pérez-Arjona, Isabel; Silva, Fernando; Roldán, Eugenio; de Valcárcel, Germán
2004-05-17
We demonstrate two alternative techniques for controlling and stabilizing domain walls (DW) in phase-sensitive, nonlinear optical resonators. The first of them uses input pumps with spatially modulated phase and can be applied also to dark-ring cavity solitons. An optical memory based on the latter is demonstrated. Here the physical mechanism of control relies on the advection caused to any feature by the phase gradients. The second technique uses a plane wave input pump with holes of null intensity across its transverse plane, which are able to capture DWs. Here the physical mechanism of control is of topological nature. When distributed as a regular array, these holes delimit spatial optical bits which constitute an optical memory. These techniques are illustrated in a degenerate optical parametric oscillator model, but can be applied to any phase-sensitive nonlinear optical cavity.
Vortices and domain walls: 'Wormholes' in unconventional superconductors
Energy Technology Data Exchange (ETDEWEB)
Bessarab, P F [St. Petersburg State University, Universitetskaya nab. 7/9, 199164 St. Petersburg (Russian Federation); Radievsky, A V, E-mail: van_der_paul@yahoo.co.u [Immanuel Kant State University of Russia, Nevskogo str. 14, 236016 Kaliningrad (Russian Federation)
2010-01-15
In the framework of the 2D and 3D time-dependent Ginzburg-Landau model we study superconductors with multicomponent order parameter (d-pairing). We argue that topological defects inside the sample do affect its thermodynamic properties such as hysteresis loop, susceptibility, etc. Along with earlier known topological defects such as Abrikosov vortices, domain walls (DWs) which separate different magnetic phases and even vortices inside the DW, we found an interesting combination of DWs and vortices. Namely we show that equivalent magnetic phases may be linked together with a vortex going through the other magnetic phase. This configuration may correspond to a stable state even in a zero external magnetic field. We also mention that this configuration is topologically similar to the 'wormholes' in the quantum gravity.
Domain walls, fusion rules, and conformal field theory in the quantum Hall regime.
Ardonne, Eddy
2009-05-08
We provide a simple way to obtain the fusion rules associated with elementary quasiholes over quantum Hall wave functions, in terms of domain walls. The knowledge of the fusion rules is helpful in the identification of the underlying conformal field theory describing the wave functions. We show that, for a certain two-parameter family (k,r) of wave functions, the fusion rules are those of su(r)k. In addition, we give an explicit conformal field theory construction of these states, based on the Mk(k+1,k+r) "minimal" theories. For r=2, these states reduce to the Read-Rezayi states. The "Gaffnian" wave function is the prototypical example for r>2, in which case the conformal field theory is nonunitary.
Manipulating ultracold atoms with a reconfigurable nanomagnetic system of domain walls
West, Adam D; Hayward, Thomas J; Fry, Paul W; Schrefl, Thomas; Gibbs, Mike R J; Adams, Charles S; Allwood, Dan A; Hughes, Ifan G
2011-01-01
The divide between the realms of atomic-scale quantum particles and lithographically-defined nanostructures is rapidly being bridged. Hybrid quantum systems comprising ultracold gas-phase atoms and substrate-bound devices already offer exciting prospects for quantum sensors, quantum information and quantum control. Ideally, such devices should be scalable, versatile and support quantum interactions with long coherence times. Fulfilling these criteria is extremely challenging as it demands a stable and tractable interface between two disparate regimes. Here we demonstrate an architecture for atomic control based on domain walls (DWs) in planar magnetic nanowires that provides a tunable atomic interaction, manifested experimentally as the reflection of ultracold atoms from a nanowire array. We exploit the magnetic reconfigurability of the nanowires to quickly and remotely tune the interaction with high reliability. This proof-of-principle study shows the practicability of more elaborate atom chips based on magn...
Energy Technology Data Exchange (ETDEWEB)
Eltschka, Matthias; Krzyk, Stephen; Nowak, Ulrich; Klaeui, Mathias [Fachbereich Physik, Universitaet Konstanz, Universitaetsstrasse 10, 78457 Konstanz (Germany); Woetzel, Mathias [Fachbereich Physik, Universitaet Konstanz, Universitaetsstrasse 10, 78457 Konstanz (Germany); Center for Electron Nanoscopy, Technical University of Denmark, 2800 Kgs. Lyngby (Denmark); Kasama, Takeshi; Dunin-Borkowski, Rafal [Center for Electron Nanoscopy, Technical University of Denmark, 2800 Kgs. Lyngby (Denmark); Rhensius, Jan [Fachbereich Physik, Universitaet Konstanz, Universitaetsstrasse 10, 78457 Konstanz (Germany); Laboratory for Micro- and Nanotechnology, Paul Scherrer Institut, 5232 Villigen PSI (Switzerland); Heyderman, Laura [Laboratory for Micro- and Nanotechnology, Paul Scherrer Institut, 5232 Villigen PSI (Switzerland)
2010-07-01
The understanding of the interplay between spin-polarized currents and magnetization as well as the determination of the spin torque terms are of scientific interest and essential for many proposed applications. Using transmission electron microscopy we investigate thermally activated domain walls (DWs) jumping back and forth between two pinning sites in permalloy wires at room temperature. The motion is of pure thermal origin without the influence of external magnetic fields or electron currents. Considering the DW as a quasi particle in a local potential with two metastable states we show that this DW movement can be described by an Arrhenius law. Subsequently, we investigate the change of the local potential by constant currents which are far below the threshold values needed for DW propagation and do not induce significant heating. Based on a 1D description of the spin transfer torque effect and the Arrhenius law we derive the non-adiabatic coefficient {beta} for a transverse and a vortex DW.
Domain wall depinning from notches using combined in- and out-of-plane magnetic fields
Directory of Open Access Journals (Sweden)
Jelle J. W. Goertz
2016-05-01
Full Text Available Controlled domain wall motion and pinning in nanowires with perpendicular magnetic anisotropy are of great importance in modern magnetic memory and logic devices. Here, we investigate by experiment the DW pinning and depinning from a notch in a magnetic nanowire, under the influence of combined in- and out-of-plane magnetic fields. In our experiment, the perpendicular magnetization of the Co/Pt nanowires is tilted with the help of sub-μs in-plane field pulses generated by an on-chip coil. Consequently, the energy density of the DW is decreased and the depinning field of the notch is reduced. A theoretical model is applied and compared to the measurement results. The DW depinning mechanism and the DW type are further investigated by micromagnetic simulations.
Steady-state configurations of Dzyaloshinskii domain walls driven by field and current
Sánchez-Tejerina, L.; Alejos, O.; Martínez, E.
2017-02-01
The dynamics of Dzyaloshinskii domain walls (DDW) in ultrathin ferromagnetic strips with perpendicular magnetic anisotropy, for different values of both perpendicular field and longitudinal current excitation associated to the Spin-Hall effect, has been studied, taking into account different values of the interfacial Dzyaloshinskii-Moriya interaction (DMI). This study has been carried out with the help of the q-Φ one-dimensional model and micromagnetic simulations. We have found that Walker breakdown may be avoided by applying a certain threshold current, even though the inverse effect is also possible. We have also found that, for particular values of field and current, the magnetization within the DDW experiences an abrupt change of orientation, which provokes a change on the contribution of current to the terminal DDW velocity. This effect disappears for sufficiently strong DMI, as it is expected from the model.
Hou, H.-C.; Kirby, B. J.; Gao, K. Z.; Lai, C.-H.
2013-04-01
We have studied the N-dependent switching behavior of composite magnets, comprised of a hard CoPtCr-SiO2 (CPCS) film and a laminated soft [Pt/CPCS]N multilayer. First order reversal curve magnetometry provides evidence of interfacial domain wall (iDW) assisted reversal for N ≥ 5. The magnetic depth profiles determined from polarized neutron reflectometry (PNR) explicitly demonstrate that the composite magnets are more rigidly coupled for N = 3 than for N = 7, and suggest that for N = 7 reversal occurs via formation of iDW. By fitting the PNR profile into the energy surface calculations, we can further deduce the vertical coupling strength in the laminated soft layer.
Topological Susceptibility in Two Flavors Lattice QCD with the Optimal Domain-Wall Fermion
Chiu, Ting-Wai; Mao, Yao-Yuan
2011-01-01
We determine the topological susceptibility of the gauge configurations generated by lattice simulations using two flavors of optimal domain-wall fermion on the $ 16^3 \\times 32 $ lattice with length 16 in the fifth dimension, at the lattice spacing $ a \\simeq 0.1 $ fm. Using the adaptive thick-restart Lanczos algorithm, we project the low-lying eigenmodes of the overlap Dirac operator, and obtain the topological charge of each configuration, for eight ensembles with pion masses in the range $ 220-550 $ MeV. From the topological charge, we compute the topological susceptibility and the second normalized cumulant. Our result of the topological susceptibility agrees with the sea-quark mass dependence predicted by the chiral perturbation theory and provides a determination of the chiral condensate, $\\Sigma^{\\bar{MS}}(2 GeV)=[259(6)(7) MeV]^3 $, and the pion decay constant $F_\\pi = 92(12)(2)$ MeV.
On-chip manipulation of magnetic nanoparticles through domain walls conduits
Vavassori, P; Donolato, M; Metlushko, V; Ilic, B; Cantoni, M; Petti, D; Brivio, S; Bertacco, R
2009-01-01
The manipulation of geometrically constrained magnetic domain walls (DWs) in nanoscale magnetic strips has attracted much interest recently, with proposals for prospective memory and logic devices. Here we propose to use the high controllability of the motion of geometrically constrained DWs for the manipulation of individual nanoparticles on a chip with an active control of position at the nanometer scale. The proposed method exploits the fact that magnetic nanoparticles in solution can be captured by a DW, whose position can be manipulated with nanometric accuracy in a specifically designed magnetic nanowire structure. We show that the high control over DW nucleation, displacement, and annihilation processes in such structures can be used to capture, transport and release magnetic nanoparticles. As magnetic particles with functionalized surfaces are commonly used as molecule carriers or labels, the accurate control over the handling of the single magnetic nanoparticle is crucial for several applications inc...
Feasible domain of Walker's unsteady wall-layer model for the velocity profile in turbulent flows
Directory of Open Access Journals (Sweden)
MIKHAIL D. MIKHAILOV
2014-12-01
Full Text Available The present work studies, in detail, the unsteady wall-layer model of Walker et al. (1989, AIAA J., 27, 140 – 149 for the velocity profile in turbulent flows. Two new terms are included in the transcendental non-linear system of equations that is used to determine the three main model parameters. The mathematical and physical feasible domains of the model are determined as a function of the non-dimensional pressure gradient parameter (p+. An explicit parameterization is presented for the average period between bursts (, the origin of time ( and the integration constant of the time dependent equation (A0 in terms of p+. In the present procedure, all working systems of differential equations are transformed, resulting in a very fast computational procedure that can be used to develop real-time flow simulators.
Feasible domain of Walker's unsteady wall-layer model for the velocity profile in turbulent flows.
Mikhailov, Mikhail D; Freire, Atila P Silva
2014-12-01
The present work studies, in detail, the unsteady wall-layer model of Walker et al. (1989, AIAA J., 27, 140 – 149) for the velocity profile in turbulent flows. Two new terms are included in the transcendental nonlinear system of equations that is used to determine the three main model parameters. The mathematical and physical feasible domains of the model are determined as a function of the non-dimensional pressure gradient parameter (p+). An explicit parameterization is presented for the average period between bursts (T+B), the origin of time (t+0 ) and the integration constant of the time dependent equation (A0) in terms of p+. In the present procedure, all working systems of differential equations are transformed, resulting in a very fast computational procedure that can be used to develop real-time flow simulators.
Oscillons, solitons, and domain walls in arrays of nonlinear plasmonic nanoparticles.
Noskov, Roman; Belov, Pavel; Kivshar, Yuri
2012-01-01
The study of metal nanoparticles plays a central role in the emerging novel technologies employing optics beyond the diffraction limit. Combining strong surface plasmon resonances, high intrinsic nonlinearities and deeply subwavelength scales, arrays of metal nanoparticles offer a unique playground to develop novel concepts for light manipulation at the nanoscale. Here we suggest a novel principle to control localized optical energy in chains of nonlinear subwavelength metal nanoparticles based on the fundamental nonlinear phenomenon of modulation instability. In particular, we demonstrate that modulation instability can lead to the formation of long-lived standing and moving nonlinear localized modes of several distinct types such as bright and dark solitons, oscillons, and domain walls. We analyze the properties of these nonlinear localized modes and reveal different scenarios of their dynamics including transformation of one type of mode to another. We believe this work paves a way towards the development of nonlinear nanophotonics circuitry.
Easy moment direction and antiferromagnetic domain wall motion in Mn{sub 2}Au
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Barthem, Vitoria M.T.S. [Instituto de Fisica, Universidade Federal do Rio de Janeiro, Cidade Universitaria, Ilha do Fundao, 21941-972 Rio de Janeiro (Brazil); Colin, Claire V.; Haettel, Richard; Dufeu, Didier [Université Grenoble Alpes, Institut NEEL, 25 Avenue des Martyrs, BP 166, F-38042 Grenoble (France); CNRS, Institut NEEL, 25 Avenue des Martyrs, BP 166, F-38042 Grenoble (France); Givord, Dominique, E-mail: dominique.givord@neel.cnrs.fr [Instituto de Fisica, Universidade Federal do Rio de Janeiro, Cidade Universitaria, Ilha do Fundao, 21941-972 Rio de Janeiro (Brazil); Université Grenoble Alpes, Institut NEEL, 25 Avenue des Martyrs, BP 166, F-38042 Grenoble (France); CNRS, Institut NEEL, 25 Avenue des Martyrs, BP 166, F-38042 Grenoble (France)
2016-05-15
The interest of giving active functions to antiferromagnetic (AFM) materials in spintronics devices has been realized recently. Mn{sub 2}Au is a high-Néel temperature antiferromagnet with large Mn moment, lying in plane of the tetragonal structure. To determine the direction of the moments in Mn{sub 2}Au, an original approach is demonstrated, which should be generic to planar AFM materials. It involves the rotation of the granular sample around an axis perpendicular to the applied magnetic field. The family of easy moment directions is 〈110〉. For grains prevented from rotating, the dominant magnetization process is AFM domain wall motion. Textured Mn{sub 2}Au nanoelements could be introduced in spintronics devices, in which the Mn moments would be switched under modest external excitation.
Magnetic domain wall motion in Co/Ni nanowires induced by a sloped electric field
Yamada, Keisuke; Murayama, Soh; Nakatani, Yoshinobu
2016-05-01
We report the sloped-electric-field (SEF)-driven motion of a magnetic domain wall (DW) in a Co/Ni nanowire with a perpendicular anisotropy using micromagnetic simulations. The results show that the DW velocity increases in proportion to the modulation ratio of the SEF, and rapidly decreases above a threshold ratio of SEF (i.e., the breakdown). We derived the analytical equation of the effective magnetic field caused by the SEF, and show the resultant DW velocity. Also, we found that the maximum DW velocity is three times faster when the Dzyaloshinskii-Moriya interaction is 0.06 erg/cm2. The results presented here offer a promising route for the design of non-volatile memory and logic devices using only the electric-field.
Neutron and proton electric dipole moments from Nf=2 +1 domain-wall fermion lattice QCD
Shintani, Eigo; Blum, Thomas; Izubuchi, Taku; Soni, Amarjit; Rbc; Ukqcd Collaborations
2016-05-01
We present a lattice calculation of the neutron and proton electric dipole moments (EDMs) with Nf=2 +1 flavors of domain-wall fermions. The neutron and proton EDM form factors are extracted from three-point functions at the next-to-leading order in the θ vacuum of QCD. In this computation, we use pion masses of 0.33 and 0.42 GeV and 2.7 fm3 lattices with Iwasaki gauge action, and a 0.17 GeV pion and a 4.6 fm3 lattice with I-DSDR gauge action, all generated by the RBC and UKQCD collaborations. The all-mode averaging technique enables an efficient and high statistics calculation. Chiral behavior of lattice EDMs is discussed in the context of baryon chiral perturbation theory. In addition, we also show numerical evidence on the relationship of three- and two-point correlation functions with the local topological charge distribution.
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Fancher, C.M.; Brewer, S.; Chung, C.C.; Röhrig, S.; Rojac, T.; Estevesa, G.; Deluca, M.; Bassiri-Gharb, N.; Jones, J.L. (Mat. Cent. Leoben); (NCSU); (Joseph Stefan Inst.); (GIT)
2017-03-01
The contribution of 180° domain wall motion to polarization and dielectric properties of ferroelectric materials has yet to be determined experimentally. In this paper, an approach for estimating the extent of (180°) domain reversal during application of electric fields is presented. We demonstrate this method by determining the contribution of domain reversal to polarization in soft lead zirconate titanate during application of strong electric fields. At the maximum applied field, domain reversal was determined to account for >80% of the measured macroscopic polarization. We also apply the method to quantify the contribution of domain reversal to the weak-field dielectric permittivity of BaTiO_{3}. The results of this analysis determined that domain reversal accounts for up to ~70% of the macroscopic dielectric permittivity in BaTiO_{3}. These results demonstrate the predominance of domain reversal to high and low-field dielectric response in ferroelectric polycrystalline materials.
Unstable equilibrium point in chaotic domain-wall motion and Ott{endash}Grebogi{endash}Yorke control
Energy Technology Data Exchange (ETDEWEB)
Okuno, H.; Takemura, Y.
2001-06-01
A method for finding the unstable equilibrium points in Bloch wall motion is proposed, which is important for controlling the chaotic domain-wall motion by using the Ott{endash}Grebogi{endash}Yorke (OGY) method. The dynamics of Bloch wall motion are expressed by a nonlinear differential equation with the terms of inertia, damping, restoring, and an external magnetic drive force. An equation is transformed into the difference equations by following the OGY method, approximating linearly around an unstable equilibrium point (a saddle point), and adding a controlling input. The unstable equilibrium points are obtained by using the return map and the condition of hyperbolic fixed point. The time series of domain-wall motion successfully controlled on the unstable equilibrium points by the OGY method is shown. {copyright} 2001 American Institute of Physics.
Energy Technology Data Exchange (ETDEWEB)
Murakami, Hiroshi; Takahashi, Kouta; Komine, Takashi; Sugita, Ryuji, E-mail: komine@mx.ibaraki.ac.j [4-12-1 Nakanarusawa, Hitachi, Ibaraki 316-8511, Ibaraki University (Japan)
2010-01-01
The current-driven domain wall motion of a multi-bit in a magnetic nanowire with perpendicular magnetic anisotropy has been analyzed by performing a micromagnetic simulation. The multi-bit motion is determined by the applied current density and the non-adiabatic spin torque parameters, which is similar to the current-driven domain wall motion of the single wall. Consequently, it was found that are two modes in the multi-bit motion: (a) the bit length remains constant and (b) the bit length varies or the bit vanishes in the nanowire. It was found that these modes of the multi-bit motion can be classified by the critical current density or Walker breakdown for the single wall motion in a magnetic nanowire with perpendicular magnetic anisotropy.
Shepley, P M; Rushforth, A W; Wang, M; Burnell, G; Moore, T A
2015-01-21
The perpendicular magnetic anisotropy K(eff), magnetization reversal, and field-driven domain wall velocity in the creep regime are modified in Pt/Co(0.85-1.0 nm)/Pt thin films by strain applied via piezoelectric transducers. K(eff), measured by the extraordinary Hall effect, is reduced by 10 kJ/m(3) by tensile strain out-of-plane ε(z) = 9 × 10(-4), independently of the film thickness, indicating a dominant volume contribution to the magnetostriction. The same strain reduces the coercive field by 2-4 Oe, and increases the domain wall velocity measured by wide-field Kerr microscopy by 30-100%, with larger changes observed for thicker Co layers. We consider how strain-induced changes in the perpendicular magnetic anisotropy can modify the coercive field and domain wall velocity.
Dobák, Samuel; Füzer, Ján; Kollár, Peter; Fáberová, Mária; Bureš, Radovan
2017-03-01
This study sheds light on the dynamic magnetization process in iron/resin soft magnetic composites from the viewpoint of quantitative decomposition of their complex permeability spectra into the viscous domain wall motion and magnetization rotation. We present a comprehensive view on this phenomenon over the broad family of samples with different average particles dimension and dielectric matrix content. The results reveal the pure relaxation nature of magnetization processes without observation of spin resonance. The smaller particles and higher amount of insulating resin result in the prevalence of rotations over domain wall movement. The findings are elucidated in terms of demagnetizing effects rising from the heterogeneity of composite materials.
Domain wall motion and precursor dynamics in PbZrO3
Puchberger, S.; Soprunyuk, V.; Majchrowski, A.; Roleder, K.; Schranz, W.
2016-12-01
Single crystals of PbZrO3 have been studied by dynamic mechanical analysis measurements in the low-frequency range f =0.02 -50 Hz. The complex Young's modulus exhibits a quite rich behavior and depends strongly on the direction of the applied dynamic force. In pseudocubic [100] c direction, we found intrinsic elastic behavior as expected from the Landau theory; at the antiferroelectric transition Tc≈510 K, a downwards cusp anomaly in Y' accompanied by a peak in Y'' points to a quadratic/linear order parameter/strain coupling in the Landau free energy. Both anomalies are increasing with decreasing frequency showing that the measurements are performed in the limit ω τth>1 . Frequency scans around Tc show energy dissipation, which could result from interphase boundary motion and/or heat diffusion. Above Tc, we observe a pronounced precursor softening, quite similar as it was found in other perovskites, which can be perfectly fitted including isotropic order parameter fluctuations. The low-frequency elastic response in [110] c direction is different. Below Tc, we find in addition to the intrinsic anomaly a strong contribution from ferroelastic domains, which leads to an additional softening in Y'. With decreasing temperatures this superelastic softening gradually disappears, due to an increasing relaxation time τDW for domain wall motion, indicating glassy behavior of domain freezing in PbZrO3. In contrast to the [100] c direction, for forces along [110] c, we found a pronounced precursor hardening, starting at about 60 K above Tc. Since this anomaly is of dynamic nature, starting at the same temperature as the observed birefringence and piezoelectric anomalies [Ko et al. Phys. Rev. B 87, 184110 (2013), 10.1103/PhysRevB.87.184110], we conclude that it originates from slow dynamic polar clusters, which freeze at T*≈550 K>Tc .
Microscopic origin of magnetoresistance
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Christian Heiliger
2006-11-01
Full Text Available Tunneling magnetoresistance is one of the basic effects of spintronics with the potential for applications in sensors and IT, where the spin degree of freedom of electrons is exploited. Successful application requires control of the materials and processes involved on the atomic scale. To support experimental developments, predict new materials, and optimize the effect, first-principle electronic structure calculations based on density functional theory are the most powerful tool. The method gives an insight into the microscopic origin of spin-dependent tunneling. The main components of a planar tunnel junction – barrier, leads, and their interface – and their specific role for tunneling magnetoresistance are discussed for one of the standard systems, Fe/MgO/Fe.
Magnetoresistive emulsion analyzer.
Lin, Gungun; Baraban, Larysa; Han, Luyang; Karnaushenko, Daniil; Makarov, Denys; Cuniberti, Gianaurelio; Schmidt, Oliver G
2013-01-01
We realize a magnetoresistive emulsion analyzer capable of detection, multiparametric analysis and sorting of ferrofluid-containing nanoliter-droplets. The operation of the device in a cytometric mode provides high throughput and quantitative information about the dimensions and magnetic content of the emulsion. Our method offers important complementarity to conventional optical approaches involving ferrofluids, and paves the way to the development of novel compact tools for diagnostics and nanomedicine including drug design and screening.
Direct observation of charged domain walls in hybrid improper ferroelectric (Ca,Sr)3Ti2O7
Kurushima, Kousuke; Yoshimoto, Wataru; Ishii, Yui; Cheong, Sang-Wook; Mori, Shigeo
2017-10-01
We investigated ferroelectric (FE) domain wall structures including “charged domain walls” of hybrid improper FE (Ca,Sr)3Ti2O7 at the subatomic resolution by dark-field transmission electron microscopy (TEM) and high-resolution state-of-the-art aberration-corrected high-angle annular-dark-field (HAADF) scanning transmission electron microscopy (STEM). Dark-field TEM and high-resolution HAADF-STEM images obtained in the FE phase of single crystals of Ca2.46Sr0.54Ti2O7 revealed the formation of abundant charged domain walls with the head-to-head and tail-to-tail configurations in the FE domain structure, in addition to the FE 180° domain structure. The charged domain walls with the head-to-head and tail-to-tail FE polarizations exist stably and can be characterized as the unique double arc-type displacement of Ca/Sr ions in a unit cell without charge accumulation.
Damjanovic, D
1997-01-01
The contribution from the irreversible displacement of non-180 deg domain walls to the direct longitudinal piezoelectric d sub 3 sub 3 coefficient of BaTiO sub 3 and Pb(Zr, Ti)O sub 3 ceramics was determined quantitatively by using the Rayleigh law. Effects of the crystal structure and microstructure of the ceramics as well as the external d.c. pressure on the domain wall contribution to d sub 3 sub 3 were examined. In barium titanate, this domain wall contribution is large (up to 35% of the total d sub 3 sub 3 , under the experimental conditions used) and dependent on the external d.c. pressure in coarse grained ceramics, and much smaller and independent of the external d.c. pressure in fine-grained samples. The presence of internal stresses in fine-grained ceramics could account for the observed behaviour. The analysis shows that the domain-wall contribution to the d sub 3 sub 3 in lead zirconate titanate ceramics is large in compositions close to the morphotropic phase boundary that contain a mixture of te...
Lin, Weiwei; Vernier, Nicolas; Agnus, Guillaume; Garcia, Karin; Ocker, Berthold; Zhao, Weisheng; Fullerton, Eric E.; Ravelosona, Dafiné
2016-11-01
Electric field effects in ferromagnetic metal/dielectric structures provide a new route to control domain wall dynamics with low-power dissipation. However, electric field effects on domain wall velocities have only been observed so far in the creep regime where domain wall velocities are low due to strong interactions with pinning sites. Here we show gate voltage modulation of domain wall velocities ranging from the creep to the flow regime in Ta/Co40Fe40B20/MgO/TiO2 structures with perpendicular magnetic anisotropy. We demonstrate a universal description of the role of applied electric fields in the various pinning-dependent regimes by taking into account an effective magnetic field being linear with the electric field. In addition, the electric field effect is found to change sign in the Walker regime. Our results are consistent with voltage-induced modification of magnetic anisotropy. Our work opens new opportunities for the study and optimization of electric field effect at ferromagnetic metal/insulator interfaces.
Domain walls and perturbation theory in high temperature gauge theory SU(2) in 2+1 dimensions
Korthals-Altes, C P; Stephanov, M A; Teper, M; Altes, C Korthals
1997-01-01
We study the detailed properties of Z_2 domain walls in the deconfined high temperature phase of the d=2+1 SU(2) gauge theory. These walls are studied both by computer simulations of the lattice theory and by one-loop perturbative calculations. The latter are carried out both in the continuum and on the lattice. We find that leading order perturbation theory reproduces the detailed properties of these domain walls remarkably accurately even at temperatures where the effective dimensionless expansion parameter, g^2/T, is close to unity. The quantities studied include the surface tension, the action density profiles, roughening and the electric screening mass. It is only for the last quantity that we find an exception to the precocious success of perturbation theory. All this shows that, despite the presence of infrared divergences at higher orders, high-T perturbation theory can be an accurate calculational tool.
Energy Technology Data Exchange (ETDEWEB)
Sun, H.Y. E-mail: hysun@165e.com; Hu, H.N.; Sun, Y.P.; Nie, X.F
2004-08-01
Influence of rotating in-plane field on vertical Bloch lines in the walls of second kind of dumbbell domains (IIDs) was investigated, and a critical in-plane field range [H{sub ip}{sup 1},H{sub ip}{sup 2}] of which vertical-Bloch lines (VBLs) annihilated in IIDs is found under rotating in-plane field (H{sub ip}{sup 1} is the maximal critical in-plane-field of which hard domains remain stable, H{sub ip}{sup 2} is the minimal critical in-plane-field of which all of the hard domains convert to soft bubbles (SBs, without VBLs)). It shows that the in-plane field range [H{sub ip}{sup 1}, H{sub ip}{sup 2}] changes with the change of the rotating angle {delta}{phi} H{sub ip}{sup 1} maintains stable, while H{sub ip}{sup 2} decreases with the decreasing of rotating angle {delta}{phi}. Comparing it with the spontaneous shrinking experiment of IIDs under both bias field and in-plane field, we presume that under the application of in-plane field there exists a direction along which the VBLs in the domain walls annihilate most easily, and it is in the direction that domain walls are perpendicular to the in-plane field.
Interlocked chiral/polar domain walls and large optical rotation in Ni3TeO6
Directory of Open Access Journals (Sweden)
Xueyun Wang
2015-07-01
Full Text Available Chirality, i.e., handedness, pervades much of modern science from elementary particles, DNA-based biology to molecular chemistry; however, most of the chirality-relevant materials have been based on complex molecules. Here, we report inorganic single-crystalline Ni3TeO6, forming in a corundum-related R3 structure with both chirality and polarity. These chiral Ni3TeO6 single crystals exhibit a large optical specific rotation (α—1355° dm−1 cm3 g−1. We demonstrate, for the first time, that in Ni3TeO6, chiral and polar domains form an intriguing domain pattern, resembling a radiation warning sign, which stems from interlocked chiral and polar domain walls through lowering of the wall energy.
Interlocked chiral/polar domain walls and large optical rotation in Ni{sub 3}TeO{sub 6}
Energy Technology Data Exchange (ETDEWEB)
Wang, Xueyun; Huang, Fei-Ting [Rutgers Center for Emergent Materials and Department of Physics and Astronomy, Rutgers University, Piscataway, New Jersey 08854 (United States); Yang, Junjie [Laboratory for Pohang Emergent Materials and Max Plank POSTECH Center for Complex Phase Materials, Pohang University of Science and Technology, Pohang 790-784 (Korea, Republic of); Oh, Yoon Seok [Rutgers Center for Emergent Materials and Department of Physics and Astronomy, Rutgers University, Piscataway, New Jersey 08854 (United States); Department of Physics, Ulsan National Institute of Science and Technology (UNIST), Ulsan 689-798 (Korea, Republic of); Cheong, Sang-Wook, E-mail: sangc@physics.rutgers.edu [Rutgers Center for Emergent Materials and Department of Physics and Astronomy, Rutgers University, Piscataway, New Jersey 08854 (United States); Laboratory for Pohang Emergent Materials and Max Plank POSTECH Center for Complex Phase Materials, Pohang University of Science and Technology, Pohang 790-784 (Korea, Republic of)
2015-07-01
Chirality, i.e., handedness, pervades much of modern science from elementary particles, DNA-based biology to molecular chemistry; however, most of the chirality-relevant materials have been based on complex molecules. Here, we report inorganic single-crystalline Ni{sub 3}TeO{sub 6}, forming in a corundum-related R3 structure with both chirality and polarity. These chiral Ni{sub 3}TeO{sub 6} single crystals exhibit a large optical specific rotation (α)—1355° dm{sup −1} cm{sup 3} g{sup −1}. We demonstrate, for the first time, that in Ni{sub 3}TeO{sub 6}, chiral and polar domains form an intriguing domain pattern, resembling a radiation warning sign, which stems from interlocked chiral and polar domain walls through lowering of the wall energy.
Ma, Yitao; Miura, Sadahiko; Honjo, Hiroaki; Ikeda, Shoji; Hanyu, Takahiro; Ohno, Hideo; Endoh, Tetsuo
2017-04-01
A high-density nonvolatile associative memory (NV-AM) based on spin transfer torque magnetoresistive random access memory (STT-MRAM), which achieves highly concurrent and ultralow-power nearest neighbor search with full adaptivity of the template data format, has been proposed and fabricated using the 90 nm CMOS/70 nm perpendicular-magnetic-tunnel-junction hybrid process. A truly compact current-mode circuitry is developed to realize flexibly controllable and high-parallel similarity evaluation, which makes the NV-AM adaptable to any dimensionality and component-bit of template data. A compact dual-stage time-domain minimum searching circuit is also developed, which can freely extend the system for more template data by connecting multiple NM-AM cores without additional circuits for integrated processing. Both the embedded STT-MRAM module and the computing circuit modules in this NV-AM chip are synchronously power-gated to completely eliminate standby power and maximally reduce operation power by only activating the currently accessed circuit blocks. The operations of a prototype chip at 40 MHz are demonstrated by measurement. The average operation power is only 130 µW, and the circuit density is less than 11 µm2/bit. Compared with the latest conventional works in both volatile and nonvolatile approaches, more than 31.3% circuit area reductions and 99.2% power improvements are achieved, respectively. Further power performance analyses are discussed, which verify the special superiority of the proposed NV-AM in low-power and large-memory-based VLSIs.
The arctic curve of the domain-wall six-vertex model
Colomo, F
2009-01-01
The problem of the form of the `arctic' curve of the six-vertex model with domain wall boundary conditions in its disordered regime is addressed. It is well-known that in the scaling limit the model exhibits phase-separation, with regions of order and disorder sharply separated by a smooth curve, called the arctic curve. To find this curve, we study a multiple integral representation for the emptiness formation probability, a correlation function devised to detect spatial transition from order to disorder. We conjecture that the arctic curve, for arbitrary choice of the vertex weights, can be characterized by the condition of condensation of almost all roots of the corresponding saddle-point equations at the same, known, value. In explicit calculations we restrict to the disordered regime for which we have been able to compute the scaling limit of certain generating function entering the saddle-point equations. The arctic curve is obtained in parametric form and appears to be a non-algebraic curve in general;...
Chirality dependent pinning and depinning of magnetic vortex domain walls at nano-constrictions
Mohanan P, Vineeth; Kumar, P. S. Anil
2017-01-01
The implementation of magnetic domain wall (DW) based memory and logic devices critically depend on the control over DW assisted magnetization reversal processes. Here we investigate the magnetization reversal by DW injection, pinning and depinning at a geometrical constriction in permalloy nanowire (NW) driven by external in-plane magnetic field, using local electrical probes. The observations of two distinct depinning field values are identified with the help of micromagnetic simulations, as being due to vortex DWs of different chiralities. Statistical analysis gave an estimate of chirality dependent pinning probability of DWs at this constriction. The stochastic nature of the DW based reversal driven by magnetic field is revealed here. The asymmetry in the depinning field of the DWs to move to either side of constriction indicates the asymmetric nature of the barrier potential seen by the DWs. The results demonstrate the difficulties in achieving deterministic switching behavior of DW assisted reversal, and provide a platform to understand the main bottlenecks in the technological implementation of DWs.
Lattice QCD with Nf = 2 + 1 + 1 domain-wall quarks
Chen, Yu-Chih; Chiu, Ting-Wai
2017-04-01
We perform hybrid Monte Carlo simulation of (2 + 1 + 1)-flavors lattice QCD with the optimal domain-wall fermion (which has the effective 4D Dirac operator exactly equal to the Zolotarev optimal rational approximation of the overlap Dirac operator). The gauge ensemble is generated on the 323 × 64 lattice with the extent Ns = 16 in the fifth dimension, and with the plaquette gauge action at β = 6 /g2 = 6.20. The lattice spacing (a ≃ 0.063 fm) is determined by the Wilson flow, using the value √{t0} = 0.1416 (8) fm obtained by the MILC Collaboration for the (2 + 1 + 1)-flavors QCD. The masses of s and c quarks are fixed by the masses of the vector mesons ϕ (1020) and J / ψ (3097) respectively; while the mass of the u / d quarks is heavier than their physical values, with the unitary pion mass Mπ ≃ 280 MeV (and Mπ L ≃ 3). We compute the point-to-point quark propagators, and measure the time-correlation functions of meson and baryon interpolators. Our results of the mass spectra of the lowest-lying hadrons containing s and c quarks are in good agreement with the high energy experimental values, together with the predictions of the charmed baryons which have not been observed in experiments.
Lattice QCD with Nf=2+1+1 domain-wall quarks
Directory of Open Access Journals (Sweden)
Yu-Chih Chen
2017-04-01
Full Text Available We perform hybrid Monte Carlo simulation of (2+1+1-flavors lattice QCD with the optimal domain-wall fermion (which has the effective 4D Dirac operator exactly equal to the Zolotarev optimal rational approximation of the overlap Dirac operator. The gauge ensemble is generated on the 323×64 lattice with the extent Ns=16 in the fifth dimension, and with the plaquette gauge action at β=6/g2=6.20. The lattice spacing (a≃0.063 fm is determined by the Wilson flow, using the value t0=0.1416(8 fm obtained by the MILC Collaboration for the (2+1+1-flavors QCD. The masses of s and c quarks are fixed by the masses of the vector mesons ϕ(1020 and J/ψ(3097 respectively; while the mass of the u/d quarks is heavier than their physical values, with the unitary pion mass Mπ≃280 MeV (and MπL≃3. We compute the point-to-point quark propagators, and measure the time-correlation functions of meson and baryon interpolators. Our results of the mass spectra of the lowest-lying hadrons containing s and c quarks are in good agreement with the high energy experimental values, together with the predictions of the charmed baryons which have not been observed in experiments.
Kong, Minsuk; Sim, Jieun; Kang, Taejoon; Nguyen, Hoang Hiep; Park, Hyun Kyu; Chung, Bong Hyun; Ryu, Sangryeol
2015-09-01
Rapid, specific and sensitive detection of pathogenic bacteria is crucial for public health and safety. Bacillus cereus is harmful as it causes foodborne illness and a number of systemic and local infections. We report a novel phage endolysin cell wall-binding domain (CBD) for B. cereus and the development of a highly specific and sensitive surface plasmon resonance (SPR)-based B. cereus detection method using the CBD. The newly discovered CBD from endolysin of PBC1, a B. cereus-specific bacteriophage, provides high specificity and binding capacity to B. cereus. By using the CBD-modified SPR chips, B. cereus can be detected at the range of 10(5)-10(8) CFU/ml. More importantly, the detection limit can be improved to 10(2) CFU/ml by using a subtractive inhibition assay based on the pre-incubation of B. cereus and CBDs, removal of CBD-bound B. cereus, and SPR detection of the unbound CBDs. The present study suggests that the small and genetically engineered CBDs can be promising biological probes for B. cereus. We anticipate that the CBD-based SPR-sensing methods will be useful for the sensitive, selective, and rapid detection of B. cereus.
pion Kaon Scattering in full QCD with domain wall valence quarks
Energy Technology Data Exchange (ETDEWEB)
Silas Beane; Paulo Bedaque; Thomas Luu; Konstantinos Orginos; Elisabetta Pallante; Assumpta Parreno; Martin Savage
2006-07-24
We calculate the {pi}{sup +}K{sup +} scattering length at pion masses of m{sub {pi}} {approx} 290, 350, 490 and 600 MeV in fully-dynamical lattice QCD with domain-wall valence quarks and rooted staggered sea quarks. The lattice data, analyzed at next-to-leading order in chiral perturbation theory, allows an extraction of the full piK scattering amplitude at threshold. Extrapolating to the physical point gives m{sub {pi}} {alpha}{sub 3/2} = -0.0574 {+-} 0.0016{sub -0.0058}{sup +0.0024} and m{sub {pi}} {alpha}{sub 1/2} = 0.1725 {+-} 0.0017{sub -0.0156}{sup +0.0023} for the I = 3/2 and I = 1/2 scattering lengths, respectively, where the first error is statistical and the second error is an estimate of the systematic error due to truncation of the chiral expansion.
Mixed Meson Mass for Domain-Wall Valence and Staggered Sea Fermions
Energy Technology Data Exchange (ETDEWEB)
Konstantinos Orginos; Andre Walker-Loud
2007-05-01
Mixed action lattice calculations allow for an additive lattice spacing dependent mass renormalization of mesons composed of one sea and one valence quark, regardless of the type of fermion discretization methods used in the valence and sea sectors. The value of the mass renormalization depends upon the lattice actions used. This mixed meson mass shift is the most important lattice artifact to determine for mixed action calculations: because it modifies the pion mass, it plays a central role in the low energy dynamics of all hadronic correlation functions. We determine the leading order and next to leading order additive mass renormalization of valence-sea mesons for a mixed lattice action with domain-wall valence fermions and staggered sea fermions. We find that on the asqtad improved coarse MILC lattices, the leading order additive mass renormalization for the mixed mesons is Δ(am)^2 LO = 0.0409(11) which corresponds to a^2 Δ_Mix = (319 MeV)^2± (53 MeV)^2 for a = 0.125 fm. We also find significant next to leading order contributions which reduce the mass renormalization by a significant amount, such that for 0 < am_π ≤ 0.22 the mixed meson mass renormalization is well approximated by Δ(am)^2 = 0.0340 (23) or a^2δ_Mix = (290 MeV)^2 ± (76 MeV)^2. The full next-to-leading order analysis is presented in the text.
The QCD chiral transition, $\\ua$ symmetry and the Dirac spectrum using domain wall fermions
Buchoff, Michael I; Christ, Norman H; Ding, H -T; Jung, Chulwoo; Karsch, F; Mawhinney, R D; Mukherjee, Swagato; Petreczky, P; Renfrew, Dwight; Schroeder, Chris; Vranas, P M; Yin, Hantao; Lin, Zhongjie
2013-01-01
We report on a study of the finite-temperature QCD transition region for temperatures between 139 and 196 MeV, with a pion mass of 200 MeV and two space-time volumes: $24^3\\times8$ and $32^3\\times8$, where the larger volume varies in linear size between 5.6 fm (at T=139 MeV) and 4.0 fm (at T=195 MeV). These results are compared with the results of an earlier calculation using the same action and quark masses but a smaller, $16^3\\times8$ volume. The chiral domain wall fermion formulation with a combined Iwasaki and dislocation suppressing determinant ratio gauge action are used. This lattice action accurately reproduces the $\\sua$ and $\\ua$ symmetries of the continuum. Results are reported for the chiral condensates, connected and disconnected susceptibilities and the Dirac eigenvalue spectrum. We find a pseudo-critical temperature, $T_c$, of approximately 165 MeV consistent with previous results and strong finite volume dependence below $T_c$. Clear evidence is seen for $\\ua$ symmetry breaking above $T_c$ whi...
The chiral transition and U(1)_A symmetry restoration from lattice QCD using Domain Wall Fermions
Bazavov, A; Buchoff, Michael I; Cheng, Michael; Christ, N H; Ding, H -T; Gupta, Rajan; Hegde, Prasad; Jung, Chulwoo; Karsch, F; Lin, Zhongjie; Mawhinney, R D; Mukherjee, Swagato; Petreczky, P; Soltz, R A; Vranas, P M; Yin, Hantao
2012-01-01
We present results on both the restoration of the spontaneously broken chiral symmetry and the effective restoration of the anomalously broken U(1)_A symmetry in finite temperature QCD at zero chemical potential using lattice QCD. We employ domain wall fermions on lattices with fixed temporal extent N_\\tau = 8 and spatial extent N_\\sigma = 16 in a temperature range of T = 139 - 195 MeV, corresponding to lattice spacings of a \\approx 0.12 - 0.18 fm. In these calculations, we include two degenerate light quarks and a strange quark at fixed pion mass m_\\pi = 200 MeV. The strange quark mass is set near its physical value. We also present results from a second set of finite temperature gauge configurations at the same volume and temporal extent with slightly heavier pion mass. To study chiral symmetry restoration, we calculate the chiral condensate, the disconnected chiral susceptibility, and susceptibilities in several meson channels of different quantum numbers. To study U(1)_A restoration, we calculate spatial ...
Domain Wall Fermion Simulations with the Exact One-Flavor Algorithm
Murphy, D J
2016-01-01
As algorithmic developments have driven down the cost of simulating degenerate light quark pairs the relative cost of simulating single quark flavors with the Rational Hybrid Monte Carlo (RHMC) algorithm has become more expensive. TWQCD has proposed an exact one-flavor algorithm (EOFA) that allows for HMC simulations of a single quark flavor without taking a square root of the fermion determinant. We have independently implemented EOFA in the Columbia Physics System (CPS) and BAGEL Fermion Sparse-Matrix Library (BFM) for Shamir and M\\"{o}bius domain wall fermions, and begun to optimize and test our implementation against RHMC. In this talk we discuss the derivation of the EOFA action, our tests of its equivalence to RHMC, and the current state of our implementation and optimization. We find, after introducing a novel preconditioning technique for the EOFA Dirac operator, that EOFA is a factor of 2.4 times faster than RHMC per molecular dynamics trajectory for the strange quark determinant on an $N_{f} = 2+1$ ...
Polarization domain wall pulses in a microfiber-based topological insulator fiber laser
Liu, Jingmin; Li, Xingliang; Zhang, Shumin; Zhang, Han; Yan, Peiguang; Han, Mengmeng; Pang, Zhaoguang; Yang, Zhenjun
2016-07-01
Topological insulators (TIs), are novel two-dimension materials, which can act as effective saturable absorbers (SAs) in a fiber laser. Moreover, based on the evanescent wave interaction, deposition of the TI on microfiber would create an effective SA, which has combined advantages from the strong nonlinear optical response in TI material together with the sufficiently-long-range interaction length in fiber taper. By using this type of TI SA, various scalar solitons have been obtained in fiber lasers. However, a single mode fiber always exhibits birefringence, and hence can support two orthogonal degenerate modes. Here we investigate experimentally the vector characters of a TI SA fiber laser. Using the saturated absorption and the high nonlinearity of the TI SA, a rich variety of dynamic states, including polarization-locked dark pulses and their harmonic mode locked counterparts, polarization-locked noise-like pulses and their harmonic mode locked counterparts, incoherently coupled polarization domain wall pulses, including bright square pulses, bright-dark pulse pairs, dark pulses and bright square pulse-dark pulse pairs are all observed with different pump powers and polarization states.
Differential Domain Wall Propagation in Y-Shaped Permalloy Nanowire Devices
Das, Bipul; Chen, Ting-Chieh; Shiu, Deng-Shiang; Horng, Lance; Wu, Jong-Ching
2016-05-01
Here, we report an investigation of magnetic domain wall (DW) evolution and propagation in Y-shaped permalloy (Py) nanowire (NW) devices. The devices are fabricated using standard electron-beam lithography technique. Each device consists of three connected NWs that form a Y-junction structure with one branch connecting either symmetrically or asymmetrically to a circular disk for DW nucleation. The DW dynamics in the devices are studied by in situ magnetic force microscopy (MFM) by pinning the DWs to triangular notches at each branch of the two devices. We observe that the DW injection field values differ depending on whether they are connected to the circular disks symmetrically or asymmetrically. However, after they pass the Y-junctions, a selection is made by the DWs to propagate easily either through both or through only one particular outgoing branch of the devices. The experimental observations are analyzed by micromagnetic simulation. It can be inferred from the results that the influence of detailed geometrical shape of the devices leads to significantly different interactions among the innate topological defects and the notches with the injected DWs.
Stochastic domain wall depinning in permalloy nanowires with various types of notches
Directory of Open Access Journals (Sweden)
Y. Gao
2016-12-01
Full Text Available Stochastic phenomena in magnetic nanowires based on domain wall (DW motion is scientifically important thus to understand and control such behaviors are very meaningful. Here we report on the investigation of pinning and depinning of DWs in permalloy nanowires with six types of longitudinally asymmetric notches using focused magneto-optic Kerr effect (FMOKE magnetometer and magnetic force microscopy (MFM. The hysteresis loops obtained by FMOKE indicate the generation of one or two distinct depinning fields by creating one notch close to the edge of the nanowires, in comparison multiple depinning processes occur in the nanowires with two identical notches symmetrically placed along the transverse direction, indicating more remarkable stochastic DW depinning phenomena. The MFM images verify the existence of DW in each type of nanowires and the DW sizes in the latter kind of nanowires are generally larger than those in the former ones. These observations can be explained by considering the thermal perturbation and edge or surface roughness effects in nanowires.
Three-dimensional SCFTs, supersymmetric domain wall and renormalization group flow
Ahn, Changhyun; Paeng, Jinsub
2001-02-01
By analyzing SU(3)×U(1) invariant stationary point, studied earlier by Nicolai and Warner, of gauged N=8 supergravity, we find that the deformation of S7 gives rise to nontrivial renormalization group flow in a three-dimensional boundary super conformal field theory from N=8 , SO(8) invariant UV fixed point to N=2 , SU(3)×U(1) invariant IR fixed point. By explicitly constructing 28-beins u,v fields, that are an element of fundamental 56-dimensional representation of E 7, in terms of scalar and pseudo-scalar fields of gauged N=8 supergravity, we get A 1,A 2 tensors. Then we identify one of the eigenvalues of A 1 tensor with "superpotential" of de Wit-Nicolai scalar potential and discuss four-dimensional supergravity description of renormalization group flow, i.e., the BPS domain wall solutions which are equivalent to vanishing of variation of spin 1/2, 3/2 fields in the supersymmetry preserving bosonic background of gauged N=8 supergravity. A numerical analysis of the steepest descent equations interpolating two critical points is given.
Precise determination of $B_K$ and right quark masses in quenched domain-wall QCD
Nakamura, Yousuke; Taniguchi, Yusuke; Yoshié, Tomoteru
2008-01-01
We calculate non-perturbative renormalization factors at hadronic scale for $\\Delta S=2$ four-quark operators in quenched domain-wall QCD using the Schr\\"{o}dinger functional method. Combining them with the non-perturbative renormalization group running by the Alpha collaboration, our result yields the fully non-perturbative renormalization factor, which converts the lattice bare $B_K$ to the renormalization group invariant (RGI) $\\hat{B}_K$. Applying this to the bare $B_K$ previously obtained by the CP-PACS collaboration at $a^{-1}\\simeq 2, 3, 4$ GeV, we obtain $\\hat{B}_K=0.782(5)(7)$ (equivalent to $B_K^{\\bar{\\rm MS}}({\\rm NDR}, 2 {\\rm GeV}) = 0.565(4)(5)$ by 2-loop running) in the continuum limit, where the first error is statistical and the second is systematic due to the continuum extrapolation. Except the quenching error, the total error we have achieved is less than 2%, which is much smaller than the previous ones. Taking the same procedure, we obtain $m_{u,d}^{\\rm RGI}=5.613(66)$ MeV and $m_s^{\\rm RGI...
Continuum Limit of $B_K$ from 2+1 Flavor Domain Wall QCD
Aoki, Y; Blum, T; Boyle, P A; Brömmel, D; Christ, N H; Dawson, C; Izubuchi, T; Jung, C; Kelly, C; Kenway, R D; Lightman, M; Mawhinney, R D; Ohta, Shigemi; Sachrajda, C T; Scholz, E E; Soni, A; Sturm, C; Wennekers, J; Zhou, R
2010-01-01
We determine the neutral kaon mixing matrix element $B_K$ in the continuum limit with 2+1 flavors of domain wall fermions, using the Iwasaki gauge action at two different lattice spacings. These lattice fermions have near exact chiral symmetry and therefore avoid artificial lattice operator mixing. We introduce a significant improvement to the conventional NPR method in which the bare matrix elements are renormalized non-perturbatively in the RI-MOM scheme and are then converted into the MSbar scheme using continuum perturbation theory. In addition to RI-MOM, we introduce and implement four non-exceptional intermediate momentum schemes that suppress infrared non-perturbative uncertainties in the renormalization procedure. We compute the conversion factors relating the matrix elements in this family of RI-SMOM schemes and MSbar at one-loop order. Comparison of the results obtained using these different intermediate schemes allows for a more reliable estimate of the unknown higher-order contributions and hence ...
An exploratory study of heavy domain wall fermions on the lattice
Energy Technology Data Exchange (ETDEWEB)
Boyle, P. [School of Physics and Astronomy, University of Edinburgh,Edinburgh, EH9 3JZ (United Kingdom); Jüttner, A. [School of Physics and Astronomy, University of Southampton,Southampton, SO17 1BJ (United Kingdom); Marinković, M. Krstić [School of Physics and Astronomy, University of Southampton,Southampton, SO17 1BJ (United Kingdom); Theoretical Physics Department, CERN,Geneva (Switzerland); Sanfilippo, F.; Spraggs, M.; Tsang, J.T. [School of Physics and Astronomy, University of Southampton,Southampton, SO17 1BJ (United Kingdom); Collaboration: The RBC/UKQCD collaboration
2016-04-06
We report on an exploratory study of domain wall fermions (DWF) as a lattice regularisation for heavy quarks. Within the framework of quenched QCD with the tree-level improved Symanzik gauge action we identify the DWF parameters which minimise discretisation effects. We find the corresponding effective 4d overlap operator to be exponentially local, independent of the quark mass. We determine a maximum bare heavy quark mass of am{sub h}≈0.4, below which the approximate chiral symmetry and O(a)-improvement of DWF are sustained. This threshold appears to be largely independent of the lattice spacing. Based on these findings, we carried out a detailed scaling study for the heavy-strange meson dispersion relation and decay constant on four ensembles with lattice spacings in the range 2.0–5.7 GeV. We observe very mild a{sup 2} scaling towards the continuum limit. Our findings establish a sound basis for heavy DWF in dynamical simulations of lattice QCD with relevance to Standard Model phenomenology.
Spin-orbit torques for current parallel and perpendicular to a domain wall
Energy Technology Data Exchange (ETDEWEB)
Schulz, Tomek; Lee, Kyujoon; Karnad, Gurucharan V. [Institut für Physik, Johannes Gutenberg-Universität Mainz, Staudinger Weg 7, 55128 Mainz (Germany); Alejos, Oscar [Departamento de Electricidad y Electrónica, Universidad de Valladolid, Paseo de Belen, 7, E-47011 Valladolid (Spain); Martinez, Eduardo; Moretti, Simone [Departamento Fisica Aplicada, Universidad de Salamanca, Plaza de los Caidos s/n, E-38008 Salamanca (Spain); Hals, Kjetil M. D. [Niels Bohr International Academy and the Center for Quantum Devices, Niels Bohr Institute, University of Copenhagen, 2100 Copenhagen (Denmark); Garcia, Karin; Ravelosona, Dafiné [Institut d' Electronique Fondamentale, UMR CNRS 8622, Université Paris Sud, 91405 Orsay Cedex (France); Vila, Laurent [Institut Nanosciences et Cryogénie, Université Grenoble Alpes, F-38000 Grenoble (France); Institut Nanosciences et Cryogénie, CEA, F-38000 Grenoble (France); Lo Conte, Roberto; Kläui, Mathias [Institut für Physik, Johannes Gutenberg-Universität Mainz, Staudinger Weg 7, 55128 Mainz (Germany); Graduate School of Excellence “Materials Science in Mainz” (MAINZ), Staudinger Weg 9, 55128 Mainz (Germany); Ocker, Berthold [Singulus Technologies AG, 63796 Kahl am Main (Germany); Brataas, Arne [Department of Physics, Norwegian University of Science and Technology, NO-7491 Trondheim (Norway)
2015-09-21
We report field- and current-induced domain wall (DW) depinning experiments in Ta\\Co{sub 20}Fe{sub 60}B{sub 20}\\MgO nanowires through a Hall cross geometry. While purely field-induced depinning shows no angular dependence on in-plane fields, the effect of the current depends crucially on the internal DW structure, which we manipulate by an external magnetic in-plane field. We show depinning measurements for a current sent parallel to the DW and compare its depinning efficiency with the conventional case of current flowing perpendicularly to the DW. We find that the maximum efficiency is similar for both current directions within the error bars, which is in line with a dominating damping-like spin-orbit torque (SOT) and indicates that no large additional torques arise for currents perpendicular to the DW. Finally, we find a varying dependence of the maximum depinning efficiency angle for different DWs and pinning levels. This emphasizes the importance of our full angular scans compared with previously used measurements for just two field directions (parallel and perpendicular to the DW) to determine the real torque strength and shows the sensitivity of the SOT to the precise DW structure and pinning sites.
An exploratory study of heavy domain wall fermions on the lattice
Boyle, Peter; Marinkovic, Marina Krstic; Sanfilippo, Francesco; Spraggs, Matthew; Tsang, Justus Tobias
2016-01-01
We report on an exploratory study of domain wall fermions (DWF) as a lattice regularisation for heavy quarks. Within the framework of quenched QCD with the tree-level improved Symanzik gauge action we identify the DWF parameters which minimise discretisation effects. We find the corresponding effective 4$d$ overlap operator to be exponentially local, independent of the quark mass. We determine a maximum bare heavy quark mass of $am_h\\approx 0.4$, below which the approximate chiral symmetry and O(a)-improvement of DWF are sustained. This threshold appears to be largely independent of the lattice spacing. Based on these findings, we carried out a detailed scaling study for the heavy-strange meson dispersion relation and decay constant on four ensembles with lattice spacings in the range $2.0-5.7\\,\\mathrm{GeV}$. We observe very mild $a^2$ scaling towards the continuum limit. Our findings establish a sound basis for heavy DWF in dynamical simulations of lattice QCD with relevance to Standard Model phenomenology.
NMSSM Inflation and Domain Walls from a Tri-critical Point of View
Aval, Hadi Gholian
2016-01-01
In this paper we want to study the conditions in which we could bring a universe filled with different $Z_3$ vacua created during the Next to Minimal Supersymmetric Standard Model (NMSSM) electroweak symmetry breaking at $\\textit{O} (10)^2$ GeV and a three dimensional three states diluted Potts model together in the same universality class. Then we use Cardy-Jacobsen conjecture to prove that there might be a tri-critical point in the NMSSM electroweak epoch of early universe. We prove that due to the existence of this point there would be no cosmological domain wall problem. Moreover, at this point the heat capacity and correlation length diverge which lead to a huge amount of energy release at constant temperature and a new mechanism for cosmological structure formation. Also, the entropy decrease after the tri-critical phase transition could explain the problem of low initial entropy in early universe. Finally, we combine Cardy-Jacobsen and Yaffe-Svetitsky conjectures to show that there might be a tri-criti...
Calculation of the neutron electric dipole moment with two dynamical flavors of domain wall fermions
Berruto, F; Orginos, K; Soni, A
2005-01-01
We present a study of the neutron electric dipole moment ($\\vec d_N$) within the framework of lattice QCD with two flavors of dynamical lig ht quarks. The dipole moment is sensitive to the topological structure of the gaug e fields, and accuracy can only be achieved by using dynamical, or sea quark, calc ulations. However, the topological charge evolves slowly in these calculations, le ading to a relatively large uncertainty in $\\vec d_N$. It is shown, using quenched configurations, that a better sampling of the charge d istribution reduces this problem, but because the CP even part of the fermion determinant is absent, both the topological charge dis tribution and $\\vec d_N$ are pathological in the chiral limit. We discuss the statistical and systematic uncertainties arising from the topological charge distr ibution and unphysical size of the quark mass in our calculations and prospects fo r eliminating them. Our calculations employ the RBC collaboration two flavor domain wall fermion and DBW2 gauge action l...
Theory of domain wall motion mediated magnetoelectric effects in a multiferroic composite
Petrov, V. M.; Srinivasan, G.
2014-10-01
A model is discussed for magnetoelectric (ME) interactions originating from the motion of magnetic domain walls (DWs) in a multiferroic composite of orthoferrites RFeO3 (RFO) with magnetic stripe domains and a piezoelectric such as lead magnesium niobate-lead titanate (PMN-PT). The DWs in RFO can be set in motion with an ac magnetic field up to a critical speed of 20 km/s, the highest for any magnetic system, leading to the excitation of bulk and shear magnetoacoustic waves. Thus, the ME coupling will arise from flexural deformation associated with DW motion (rather than the Joule magnetostriction mediated coupling under a static or quasistatic condition). A c plane orthoferrite with a single Néel-type DW in the bc plane and an ac magnetic field H along the c axis is assumed. The deflection in the bilayer due to DW motion is obtained when the DW velocity is a linear function H and the resulting induced voltage across PMN-PT is estimated. It is shown that a combination of spatial and time harmonics of the bending deformation leads to (i) a linear ME coefficient defined by αE=E/H and (ii) a quadratic ME coefficient αEQ=E/H2. The model is applied to yttrium orthoferrites (YFO) and a PMN-PT bilayer since YFO has one of the highest DW mobility amongst the orthoferrites. The coefficient αE is dependent on the DW position, and it is maximum when the DW equilibrium position is at the center of the sample. In YFO/PMN-PT the estimated low-frequency αE ˜ 30 mV/cm Oe and resonance value is 1.5 V/(cm Oe). Since orthoferrites (and PMN-PT) are transparent in the visible region and have a large Faraday rotation, the DW dynamics and the ME coupling could be studied simultaneously. The theory discussed here is of interest for studies on ME coupling and for applications such as magnetically controlled electro-optic devices.
Calculation of the neutron electric dipole moment with two dynamical flavors of domain wall fermions
Energy Technology Data Exchange (ETDEWEB)
F. Berruto; T. Blum; K. Orginos; A. Soni
2005-12-08
We present a study of the neutron electric dipole moment ({rvec d}{sub N}) within the framework of lattice QCD with two flavors of dynamical light quarks. The dipole moment is sensitive to the topological structure of the gauge fields, and accuracy can only be achieved by using dynamical, or sea quark, calculations. However, the topological charge evolves slowly in these calculations, leading to a relatively large uncertainty in {rvec d}{sub N}. It is shown, using quenched configurations, that a better sampling of the charge distribution reduces this problem, but because the CP even part of the fermion determinant is absent, both the topological charge distribution and {rvec d}{sub N} are pathological in the chiral limit. We discuss the statistical and systematic uncertainties arising from the topological charge distribution and unphysical size of the quark mass in our calculations and prospects for eliminating them. Our calculations employ the RBC collaboration two flavor domain wall fermion and DBW2 gauge action lattices with inverse lattice spacing a{sup -1} {approx} 1.7 GeV, physical volume V {approx} (2 fm){sup 3}, and light quark mass roughly equal to the strange quark mass (m{sub sea} = 0.03 and 0.04). We determine a value of the electric dipole moment that is zero within (statistical) errors, |{rvec d}{sub N}| = -0.04(20) e-{theta}-fm at the smaller sea quark mass. Satisfactory results for the magnetic and electric form factors of the proton and neutron are also obtained and presented.
NUCLEON STRUCTURE IN LATTICE QCD WITH DYNAMICAL DOMAIN--WALL FERMIONS QUARKS.
Energy Technology Data Exchange (ETDEWEB)
LIN H.-W.; OHTA, S.
2006-10-02
We report RBC and RBC/UKQCD lattice QCD numerical calculations of nucleon electroweak matrix elements with dynamical domain-wall fermions (DWF) quarks. The first, RBC, set of dynamical DWF ensembles employs two degenerate flavors of DWF quarks and the DBW2 gauge action. Three sea quark mass values of 0.04, 0.03 and 0.02 in lattice units are used with 220 gauge configurations each. The lattice cutoff is a{sup -1} {approx} 1.7GeV and the spatial volume is about (1.9fm){sup 3}. Despite the small volume, the ratio of the isovector vector and axial charges g{sub A}/g{sub V} and that of structure function moments
Sandmann, Christian
Understanding the mutual interaction of extrinsic and intrinsic defects with the ferroelectric domain walls of LiNbO3 is the key to achieve domain patterns on the sub-micron scale. For that reason the influence of domain inversion on the Er3+ defect was investigated in a detailed study, in which energetic shifts and changes in the intensity ratio of individual Er3+ sites were found. The results led to an improved model describing the Er3+ defect in LiNbO3 and to the introduction of a concept of an atomistic probe. This atomistic probe allows the determination of the orientation of the ferroelectric axis by means of optical spectroscopy and allows three-dimensional imaging of domain structures with high spatial resolution without topographic artifacts. For this purpose a confocal luminescence microscope was developed, adapted to allow investigation at low temperature and applied electric fields. Based on the concept of an atomistic probe, the interaction of Er and Ti dopants was investigated, and significant spectral broadening and line shifting were found. Calibrating these changes to the [Ti4+]-concentration allows imaging of [Ti4+]-profiles, as found in integrated optical devices. The [Ti4+]-concentration profile can be imaged without artifacts caused by topology, intensity fluctuations, or variations in the [Er3+]-concentration profile. A novel approach was introduced for directly writing ferroelectric domain patterns into LiNbO3 substrates using the confocal microscope to focus visible light from an argon ion laser to a diffraction limited spot. It was shown that space charge fields, created by light with a wavelength of 488nm, can reduce the external applied field needed for domain inversion by up to 30%. So far, structures with a period down to 8mum have been demonstrated. In-situ experiments during domain inversion demonstrated the possibility to monitor the domain inversion process in-situ with a temporal resolution of up to t = 7ms. It could be
Han, Myung-Geun; Garlow, Joseph A.; Bugnet, Matthieu; Divilov, Simon; Marshall, Matthew S. J.; Wu, Lijun; Dawber, Matthew; Fernandez-Serra, Marivi; Botton, Gianluigi A.; Cheong, Sang-Wook; Walker, Frederick J.; Ahn, Charles H.; Zhu, Yimei
2016-09-01
Polar discontinuity at interfaces plays deterministic roles in charge transport, magnetism, and even superconductivity of functional oxides. To date, most polar discontinuity problems have been explored in heterointerfaces between two dissimilar materials. Here, we show that charged domain walls (CDWs) in epitaxial thin films of ferroelectric PbZ r0.2T i0.8O3 are strongly coupled to polar interfaces through the formation of 1/2 {h 0 l } - type crystallographic shear planes (CSPs). Using atomic resolution imaging and spectroscopy we illustrate that the CSPs consist of both conservative and nonconservative segments when coupled to the CDWs where necessary compensating charges for stabilizing the CDWs are associated with vacancies at the CSPs. The CDW/CSP coupling yields an atomically narrow domain wall, consisting of a single atomic layer of oxygen. This study shows that the CDW/CSP coupling is a fascinating venue to develop emergent material properties.
Zeissler, Katharina; Chadha, Megha; Lovell, Edmund; Cohen, Lesley F.; Branford, Will R.
2016-07-01
Artificial spin ices are frustrated magnetic nanostructures where single domain nanobars act as macrosized spins. In connected kagome artificial spin ice arrays, reversal occurs along one-dimensional chains by propagation of ferromagnetic domain walls through Y-shaped vertices. Both the vertices and the walls are complex chiral objects with well-defined topological edge-charges. At room temperature, it is established that the topological edge-charges determine the exact switching reversal path taken. However, magnetic reversal at low temperatures has received much less attention and how these chiral objects interact at reduced temperature is unknown. In this study we use magnetic force microscopy to image the magnetic reversal process at low temperatures revealing the formation of quite remarkable high energy remanence states and a change in the dynamics of the reversal process. The implication is the breakdown of the artificial spin ice regime in these connected structures at low temperatures.
Current-induced domain wall motion in Co/Ni nano-wires with different Co and Ni thicknesses
Energy Technology Data Exchange (ETDEWEB)
Ueda, K; Chiba, D; Koyama, T; Yamada, G; Ono, T [Institute for Chemical Research, Kyoto University, Gokasho, Uji, Kyoto, 611-0011 (Japan); Tanigawa, H; Fukami, S; Suzuki, T; Ohshima, N; Ishiwata, N [NEC Corporation, 1120 Shimokuzawa, Chuo-ku, Sagamihara, Kanagawa 252-5298 (Japan); Nakatani, Y, E-mail: ono@scl.kyoto-u.ac.jp [University of Electro-communications, Chofu, Tokyo, 182-8585 (Japan)
2011-01-01
The authors have investigated magnetic domain wall motion induced by electric currents in ferromagnetic nano-wires made of Co/Ni multilayers. The thicknesses of Co and Ni layers were changed, whereas the numbers of layer stacks of Co and Ni were the same in all samples. The sample with thinner total Co/Ni thickness showed the lower threshold current density for the domain wall motion as an overall trend, which is qualitatively in agreement with the expectation by the theory based on the adiabatic spin-transfer model. The lowest threshold current density was 2.9x10{sup 11} A/m{sup 2} obtained in the sample with the total Co/Ni thickness of 3.4 nm and the wire width of 110 nm.
Aval, Hadi Gholian
2016-01-01
In this paper I will combine and use two Cardy-Jacobsen and Yaffe-Svetitsky conjectures [1, 2] to present a mechanism for a late-time inflation during the electroweak symmetry breaking due to discrete Z_3 symmetry at O(10^2 ) GeV and a psudo-inflation at O(10^2 ) MeV scale in order to solve the cosmological domain wall problem and thermal and non-thermal relics overproduction in the early universe. We will see that Cardy-Jacobsen conjecture and Zeldovic statement for cosmological domain wall problem are incompatible. Also, in the psudo-inflation mechanism presented here there would be a latent heat release and entropy injection without an exponential expansion and reheating period.
Callen, Benjamin D
2013-01-01
We present a generic Z_2 x Z_2-invariant scalar field theory with four real scalar fields in six-dimensional Minkowskian spacetime which yields solutions consisting of two intersecting domain-wall kinks which are each paired by fields with lump-like profiles. For a special parameter choice, analytic solutions can be obtained. We show that the Z_2 x Z_2 symmetry can be maintained while coupling fermions by introducing scalar Yukawa couplings to one kink-lump pair and six-dimensional pseudoscalar Yukawa couplings to the other, and we show that there exists a zero mode localized to the domain-wall junction in this case. We also show that scalar fields can be localized.
Energy Technology Data Exchange (ETDEWEB)
Bratt, Jonathan; Engelhardt, Michael; Haegler, Philipp; Huey-Wen, Lin; Lin, Meifeng; Meyer, Harvey; Musch, Bernhard; Negele, John; Orginos, Konstantinos; Pochinsky, Andrew; Procura, Massimiliano; Richards, David; Schroers, Wolfram; Syritsyn, Sergey
2010-11-01
We present high statistics results for the structure of the nucleon from a mixed-action calculation using 2+1 flavors of asqtad sea and domain wall valence fermions. We perform extrapolations of our data based on different chiral effective field theory schemes and compare our results with available information from phenomenology. We discuss vector and axial form factors of the nucleon, moments of generalized parton distributions, including moments of forward parton distributions, and implications for the decomposition of the nucleon spin.
Domain wall partition function of the eight-vertex model with a non-diagonal reflecting end
Yang, Wen-Li; Feng, Jun; Hao, Kun; Shi, Kang-Jie; Sun, Cheng-Yi; Yang, Zhan-Ying; Zhang, Yao-Zhong
2011-01-01
With the help of the Drinfeld twist or factorizing F-matrix for the eight-vertex SOS model, we obtain the explicit determinant expression of the partition function of the eight-vertex model with a generic non-diagonal reflecting end and domain wall boundary condition. Our result shows that, contrary to the eight-vertex model without a reflection end, the partition function can be expressed as a single determinant.
Superconducting magnetoresistance in ferromagnet/superconductor/ferromagnet trilayers.
Stamopoulos, D; Aristomenopoulou, E
2015-01-01
Magnetoresistance is a multifaceted effect reflecting the diverse transport mechanisms exhibited by different kinds of plain materials and hybrid nanostructures; among other, giant, colossal, and extraordinary magnetoresistance versions exist, with the notation indicative of the intensity. Here we report on the superconducting magnetoresistance observed in ferromagnet/superconductor/ferromagnet trilayers, namely Co/Nb/Co trilayers, subjected to a parallel external magnetic field equal to the coercive field. By manipulating the transverse stray dipolar fields that originate from the out-of-plane magnetic domains of the outer layers that develop at coercivity, we can suppress the supercurrent of the interlayer. We experimentally demonstrate a scaling of the magnetoresistance magnitude that we reproduce with a closed-form phenomenological formula that incorporates relevant macroscopic parameters and microscopic length scales of the superconducting and ferromagnetic structural units. The generic approach introduced here can be used to design novel cryogenic devices that completely switch the supercurrent 'on' and 'off', thus exhibiting the ultimate magnetoresistance magnitude 100% on a regular basis.
Chang, Yoonjee; Ryu, Sangryeol
2017-01-01
Endolysin from Staphylococcus aureus phage SA97 (LysSA97) was cloned and investigated. LysSA97 specifically lyse the staphylococcal strains and effectively disrupted staphylococcal biofilms. Bioinformatic analysis of LysSA97 revealed a novel putative cell wall binding domain (CBD) as well as two enzymatically active domains (EADs) containing cysteine, histidine-dependent amidohydrolases/peptidases (CHAP, PF05257) and N-acetylmuramoyl-L-alanine amidase (Amidase-3, PF01520) domains. Comparison of 98 endolysin genes of S. aureus phages deposited in GenBank showed that they can be classified into six groups based on their domain composition. Interestingly, approximately 80.61 % of the staphylococcal endolysins have a src-homology 3 (SH3, PF08460) domain as CBD, but the remaining 19.39 %, including LysSA97, has a putative C-terminal CBD with no homology to the known CBD. The fusion protein containing green fluorescent protein and the putative CBD of LysSA97 showed a specific binding spectrum against staphylococcal cells comparable to SH3 domain (PF08460), suggesting that the C-terminal domain of LysSA97 is a novel CBD of staphylococcal endolysins.
Giant magnetoresistance effect detection of magnetization reversal in single crystalline nanowires
Energy Technology Data Exchange (ETDEWEB)
Yamamoto, H; Kasatani, Y; Yamaguchi, A; Miyajima, H, E-mail: ykasatan@phys.keio.ac.j, E-mail: yamaguch@phys.keio.ac.j, E-mail: miyajima@phys.keio.ac.j [Department of Physics, Keio University, Hiyoshi, Yokohama 223-8522 (Japan)
2010-01-01
The controllable and rapid magnetization reversal in nano-scale wires is fundamental to the operation of new magnetic logic and data storage devices. A lot of previous investigations for the single domain wall (DW) dynamics in nano-scale wires have been performed by soft ferromagnetic material such as polycrystalline permalloy with negligible magnetic crystalline anisotropy. In fact, it is vital to understand the DW dynamics within the crystalline anisotropy for not only the fundamental magnetism but also potential applications. The aim of this study is to present the experimental result of magnetization reversal in epitaxial single crystalline nanowires by using giant magnetoresistance effect. The DW at the edge of the wire, and the switching field strongly depends on the crystalline anisotropy.
Speed limit in internal space of domain walls via all-order effective action of moduli motion
Eto, Minoru; Hashimoto, Koji
2016-03-01
We find that motion in internal moduli spaces of generic domain walls has an upper bound for its velocity. Our finding is based on our generic formula for all-order effective actions of internal moduli parameter of domain wall solitons. It is known that the Nambu-Goldstone mode Z associated with spontaneous breaking of translation symmetry obeys a Nambu-Goto effective Lagrangian √{1 -(∂0Z )2 } detecting the speed of light (|∂0Z |=1 ) in the target spacetime. Solitons can have internal moduli parameters as well, associated with a breaking of internal symmetries such as a phase rotation acting on a field. We obtain, for generic domain walls, an effective Lagrangian of the internal moduli ɛ to all orders in (∂ɛ ). The Lagrangian is given by a function of the Nambu-Goto Lagrangian: L =g (√{1 +(∂μɛ )2 }). This shows generically the existence of an upper bound on ∂0ɛ , i.e., a speed limit in the internal space. The speed limit exists even for solitons in some nonrelativistic field theories, where we find that ɛ is a type I Nambu-Goldstone mode that also obeys a nonlinear dispersion to reach the speed limit. This offers a possibility of detecting the speed limit in condensed matter experiments.
Speed limit in internal space of domain walls via all-order effective action of moduli motion
Eto, Minoru
2015-01-01
We find that motion in internal moduli spaces of generic domain walls has an upper bound for its velocity. Our finding is based on our generic formula for all-order effective actions of internal moduli parameter of domain wall solitons. It is known that the Nambu-Goldstone mode $Z$ associated with spontaneous breaking of translation symmetry obeys a Nambu-Goto effective Lagrangian $\\sqrt{1 - (\\partial_0 Z)^2}$ detecting the speed of light ($|\\partial_0 Z|=1$) in the target spacetime. Solitons can have internal moduli parameters as well, associated with a breaking of internal symmetries such as a phase rotation acting on a field. We obtain, for generic domain walls, an effective Lagrangian of the internal moduli $\\epsilon$ to all order in $(\\partial \\epsilon)$. The Lagrangian is given by a function of the Nambu-Goto Lagrangian: $L = g(\\sqrt{1 + (\\partial_\\mu \\epsilon)^2})$. This shows generically the existence of an upper bound on $\\partial_0 \\epsilon$, i.e. a speed limit in the internal space. The speed limit...
Consolo, Giancarlo; Valenti, Giovanna
2017-01-01
The one-dimensional propagation of magnetic domain walls in an isotropic, linearly elastic, magnetostrictive material is investigated in the framework of the extended Landau-Lifshitz-Gilbert equation where the effects of a spin-polarized current and a rate-independent dry-friction dissipation are taken into account. In our analysis, it is assumed that the ferromagnet is subject to a spatially uniform biaxial in-plain stress generated by a piezoelectric substrate combined with the former in a multiferroic heterostructure. Moreover, a possible connection between the dry-friction mechanism and the piezo-induced strains is conjectured. By adopting the traveling waves ansatz, the effect of such a stress on the domain wall dynamics is explored in both steady and precessional regimes. In particular, it is proved that the magnetoelastic contribution, while it does not formally modify the classical solution, affects both the propagation threshold and the Walker Breakdown conditions involved in the steady regime, in agreement with recent experimental results. In the precessional regime, it is shown that the existence of a correlation between the piezo-induced strains and dry-friction leads to an upward shift of the domain wall velocity.
Murein and pseudomurein cell wall binding domains of bacteria and archaea-a comparative view
Visweswaran, Ganesh Ram R.; Dijkstra, Bauke W.; Kok, Jan
2011-01-01
The cell wall, a major barrier protecting cells from their environment, is an essential compartment of both bacteria and archaea. It protects the organism from internal turgor pressure and gives a defined shape to the cell. The cell wall serves also as an anchoring surface for various proteins and a
Magnetoresistance and magnetic properties in amorphous Fe-based wires
Bordin, G.; Buttino, G.; Cecchetti, A.; Poppi, M.
2001-06-01
The longitudinal and transverse magnetoresistances in amorphous Fe 77.5Si 7.5B 15 wires are studied at different values of the DC-bias currents in order to clarify the mechanism of the magnetization according to a 'core-shell' domain model. The role of closure domain structures in the magnetization process of the wires is analysed. Moreover, the effects of the Joule heating on the internal stresses, introduced during the rapid quenching in the sample preparation, are examined.
Anomalous magnetoresistance in Fibonacci multilayers.
Energy Technology Data Exchange (ETDEWEB)
Machado, L. D.; Bezerra, C. G.; Correa, M. A.; Chesman, C.; Pearson, J. E.; Hoffmann, A. (Materials Science Division); (Universidade Federal do Rio Grande do Norte)
2012-01-01
We theoretically investigated magnetoresistance curves in quasiperiodic magnetic multilayers for two different growth directions, namely, [110] and [100]. We considered identical ferromagnetic layers separated by nonmagnetic layers with two different thicknesses chosen based on the Fibonacci sequence. Using parameters for Fe/Cr multilayers, four terms were included in our description of the magnetic energy: Zeeman, cubic anisotropy, bilinear coupling, and biquadratic coupling. The minimum energy was determined by the gradient method and the equilibrium magnetization directions found were used to calculate magnetoresistance curves. By choosing spacers with a thickness such that biquadratic coupling is stronger than bilinear coupling, unusual behaviors for the magnetoresistance were observed: (i) for the [110] case, there is a different behavior for structures based on even and odd Fibonacci generations, and, more interesting, (ii) for the [100] case, we found magnetic field ranges for which the magnetoresistance increases with magnetic field.
Delivering Single-Walled Carbon Nanotubes to the Nucleus Using Engineered Nuclear Protein Domains.
Boyer, Patrick D; Ganesh, Sairaam; Qin, Zhao; Holt, Brian D; Buehler, Markus J; Islam, Mohammad F; Dahl, Kris Noel
2016-02-10
Single-walled carbon nanotubes (SWCNTs) have great potential for cell-based therapies due to their unique intrinsic optical and physical characteristics. Consequently, broad classes of dispersants have been identified that individually suspend SWCNTs in water and cell media in addition to reducing nanotube toxicity to cells. Unambiguous control and verification of the localization and distribution of SWCNTs within cells, particularly to the nucleus, is needed to advance subcellular technologies utilizing nanotubes. Here we report delivery of SWCNTs to the nucleus by noncovalently attaching the tail domain of the nuclear protein lamin B1 (LB1), which we engineer from the full-length LMNB1 cDNA. More than half of this low molecular weight globular protein is intrinsically disordered but has an immunoglobulin-fold composed of a central hydrophobic core, which is highly suitable for associating with SWCNTs, stably suspending SWCNTs in water and cell media. In addition, LB1 has an exposed nuclear localization sequence to promote active nuclear import of SWCNTs. These SWCNTs-LB1 dispersions in water and cell media display near-infrared (NIR) absorption spectra with sharp van Hove peaks and an NIR fluorescence spectra, suggesting that LB1 individually disperses nanotubes. The dispersing capability of SWCNTs by LB1 is similar to that by albumin proteins. The SWCNTs-LB1 dispersions with concentrations ≥150 μg/mL (≥30 μg/mL) in water (cell media) remain stable for ≥75 days (≥3 days) at 4 °C (37 °C). Further, molecular dynamics modeling of association of LB1 with SWCNTs reveal that the exposure of the nuclear localization sequence is independent of LB1 binding conformation. Measurements from confocal Raman spectroscopy and microscopy, NIR fluorescence imaging of SWCNTs, and fluorescence lifetime imaging microscopy show that millions of these SWCNTs-LB1 complexes enter HeLa cells, localize to the nucleus of cells, and interact with DNA. We postulate that the
Favaloro, Tela; Suh, Joonki; Vermeersch, Bjorn; Liu, Kai; Gu, Yijia; Chen, Long-Qing; Wang, Kevin X; Wu, Junqiao; Shakouri, Ali
2014-05-14
The metal to insulator transition (MIT) of strongly correlated materials is subject to strong lattice coupling, which brings about the unique one-dimensional alignment of metal-insulator (M-I) domains along nanowires or nanobeams. Many studies have investigated the effects of stress on the MIT and hence the phase boundary, but few have directly examined the temperature profile across the metal-insulating interface. Here, we use thermoreflectance microscopy to create two-dimensional temperature maps of single-crystalline VO2 nanobeams under external bias in the phase coexisting regime. We directly observe highly localized alternating Peltier heating and cooling as well as Joule heating concentrated at the M-I domain boundaries, indicating the significance of the domain walls and band offsets. Utilizing the thermoreflectance technique, we are able to elucidate strain accumulation along the nanobeam and distinguish between two insulating phases of VO2 through detection of the opposite polarity of their respective thermoreflectance coefficients. Microelasticity theory was employed to predict favorable domain wall configurations, confirming the monoclinic phase identification.
Ekomasov, E. G.
2003-08-01
The influence of exchange relaxation on the dynamics of domain walls with a "fine structure" in rare-earth orthoferrites in the presence of external magnetic and electric fields is investigated. A system of differential equations is obtained which describe the dynamics of a domain wall with a solitary line. The dependence of the steady-state velocity of the domain wall and line on the values of the relaxation parameters and on the components of the magnetic and electric fields is found. The results are compared with the known experimental results.
Directory of Open Access Journals (Sweden)
Ganesh Ram R Visweswaran
Full Text Available We have biochemically and functionally characterized the pseudomurein cell wall-binding (PMB domain that is present at the C-terminus of the Surface (S-layer protein MTH719 from Methanothermobacter thermautotrophicus. Chemical denaturation of the protein with guanidinium hydrochloride occurred at 3.8 M. A PMB-GFP fusion protein not only binds to intact pseudomurein of methanogenic archaea, but also to spheroplasts of lysozyme-treated bacterial cells. This binding is pH dependent. At least two of the three motifs that are present in the domain are necessary for binding. Limited proteolysis revealed a possible cleavage site in the spacing sequence between motifs 1 and 2 of the PMB domain, indicating that the motif region itself is protected from proteases.
Starkov, Alexander S; Starkov, Ivan A
2013-12-01
We have proposed a new theoretical approach for the determination of the electric field distribution in the ferroelectric/dielectric system with the presence of the SPM tip. The initial statement of the model has only a numerical solution. To find an analytical solution of the problem, some assumptions are introduced: the domain wall thickness can be considered to be much smaller than the domain size, and we use a high ferroelectric dielectric permittivity. The developed approach allows us to obtain explicit formulas for the polarization and electric field intensity. We have calculated and then analyzed the tip capacitance as a function of the distance from the ferroelectric interface. Additionally, different forms of the SPM tip are considered. It is demonstrated that in the presence of charges at the domain, the results differ from those obtained with the widely used dielectric model by 30%.
Structural Insight into Fungal Cell Wall Recognition by a CVNH Protein with a Single LysM Domain.
Koharudin, Leonardus M I; Debiec, Karl T; Gronenborn, Angela M
2015-11-03
MGG_03307 is a lectin isolated from Magnaporte oryzae, a fungus that causes devastating rice blast disease. Its function is associated with protecting M. oryzae from the host immune response in plants. To provide the structural basis of how MGG_03307 protects the fungus, crystal structures of its CVNH-LysM module were determined in the absence and presence of GlcNAc-containing cell wall chitin constituents, which can act as pathogen-associated molecular patterns. Our structures revealed that glycan binding is accompanied by a notable conformational change in the LysM domain and that GlcNAc3 and GlcNAc4 are accommodated similarly. GlcNAc5 and GlcNAc6 interact with the LysM domain in multiple conformations, as evidenced by solution nuclear magnetic resonance studies. No dimerization of MoCVNH3 via its LysM domain was observed upon binding to GlcNAc6, unlike in multiple LysM domain-containing proteins. Importantly, we define a specific consensus binding mode for the recognition of GlcNAc oligomers by single LysM domains. Copyright © 2015 Elsevier Ltd. All rights reserved.
Shevchenko, Andriy; Barabash, Maksym
2015-01-01
On the basis of the method of gyrotropic Thiele forces, we build a formalism that allows the determination of the effective mass of the nanoscales structural elements of the domain wall (DW): vertical Bloch line and Bloch point in uniaxial ferromagnets. As shown, the effective mass of these magnetic inhomogeneities depends on the value of the gyrotropic domain wall bend that is created by their movement.
Kawanai, Taichi; Witzel, Oliver
2012-01-01
We report on a lattice-QCD calculation of the B to pi l nu form factor with domain-wall light quarks and relativistic b-quarks using the 2 + 1 flavor domain-wall fermion and Iwasaki gauge-field ensembles generated by the RBC and UKQCD Collaborations. We present initial results obtained from the coarser (a ~ 0.11 fm) 24^3 lattices and some of the finer (a ~ 0.086 fm) 32^3 lattices.
Directory of Open Access Journals (Sweden)
Irshad Kashif
2016-01-01
Full Text Available Maintaining indoor climatic conditions of buildings compatible with the occupant comfort by consuming minimum energy, especially in a tropical climate becomes a challenging problem for researchers. This paper aims to investigate this problem by evaluating the effect of different kind of Photovoltaic Trombe wall system (PV-TW on thermal comfort, energy consumption and CO2 emission. A detailed simulation model of a single room building integrated with PV-TW was modelled using TRNSYS software. Results show that 14-35% PMV index and 26-38% PPD index reduces as system shifted from SPV-TW to DGPV-TW as compared to normal buildings. Thermal comfort indexes (PMV and PPD lie in the recommended range of ASHARE for both DPV-TW and DGPV-TW except for the few months when RH%, solar radiation intensity and ambient temperature were high. Moreover PVTW system significantly reduces energy consumption and CO2 emission of the building and also 2-4.8 °C of temperature differences between indoor and outdoor climate of building was examined.
Optimizing the domain wall fermion Dirac operator using the R-Stream source-to-source compiler
Lin, Meifeng; Langston, M Harper; Meister, Benoit; Baskaran, Muthu; Izubuchi, Taku; Jung, Chulwoo
2015-01-01
The application of the Dirac operator on a spinor field, the Dslash operation, is the most computation-intensive part of the lattice QCD simulations. It is often the key kernel to optimize to achieve maximum performance on various platforms. Here we report on a project to optimize the domain wall fermion Dirac operator in Columbia Physics System (CPS) using the R-Stream source-to-source compiler. Our initial target platform is the Intel PC clusters. We discuss the optimization strategies involved before and after the automatic code generation with R-Stream and present some preliminary benchmark results.
Institute of Scientific and Technical Information of China (English)
Li Long; Zhang Yu; Liang Changhong
2004-01-01
An Improved Locally Conformal Finite-Difference Time-Domain (ILC-FDTD) method is presented in this paper, which is used to analyze the edge inclined slots penetrating adjacent broadwalls of a finite wall thickness waveguide. ILC-FDTD not only removes the instability of the original locally conformal FDTD algorithm, but also improves the computational accuracy by locally modifying magnetic field update equations and the virtual iterative electric fields according to the complexity of the slot fringe fields. The mutual coupling between two edge inclined slots can also be analyzed by ILC-FDTD effectively.
Skumryev, V.; Laukhin, V.; Fina, I.; Martí, X.; Sánchez, F.; Gospodinov, M.; Fontcuberta, J.
2011-02-01
We demonstrate that the magnetization of a ferromagnet in contact with an antiferromagnetic multiferroic (LuMnO3) can be speedily reversed by electric-field pulsing, and the sign of the magnetic exchange bias can switch and recover isothermally. As LuMnO3 is not ferroelastic, our data conclusively show that this switching is not mediated by strain effects but is a unique electric-field driven decoupling of the ferroelectric and antiferromagnetic domain walls. Their distinct dynamics are essential for the observed magnetic switching.
Interaction of Lamb Waves with Domain Walls in an Iron Borate Plate
Directory of Open Access Journals (Sweden)
E.A. Zhukov
2015-12-01
Full Text Available This work presents the calculation results of the Lamb wave spectra in a plate of iron borate. Experimental data on how flexural vibrations in a borate plate influence its domain structure are provided.
Topolov, V Y
1998-01-01
The paper is devoted to the determination of effective electromechanical constants d sub i sub j sup p , e sub i sub j sup p , epsilon sub k sub l supsigma sup , sup p and s sub f sub g sup E sup , sup p of polydomain LiNbO sub 3 and LiNb sub 0 sub . sub 1 Ta sub 0 sub . sub 9 O sub 3 crystals at room temperature. 180 deg domain structures considered here contain inclined plane walls providing a significant anisotropy of piezoelectric constants e sub i sub j sup p. The effect of such domain structures is established for the first time and discussed. (author)
Heide, Marcus; Bihlmayer, Gustav; Blügel, Stefan
2011-04-01
The basic micromagnetic models of Landau, Lifshitz, and Dzyaloshinskii, are extended by an anisotropy term with two independent parameters. The resulting ground states of the magnetic domains and the domain-wall profiles are discussed for crystal lattices with orthorhombic unit cells. In these simple geometries, the magnetization is not confined to a single plane. Depending on the relations between the spin-stiffness, anisotropy, and Dzyaloshinskii-Moriya interaction several different zero-temperature phases of the magnetic structure are found. The corresponding phase diagrams are obtained numerically. Analytical results are given for some special cases. The studied model is of particular relevance for magnetic wires, nanostripes and ultrathin magnetic films deposited on non-magnetic surfaces.
Tunneling magnetoresistance in Si nanowires
Montes, E.; Rungger, I.; Sanvito, S.; Schwingenschlögl, U.
2016-11-01
We investigate the tunneling magnetoresistance of small diameter semiconducting Si nanowires attached to ferromagnetic Fe electrodes, using first principles density functional theory combined with the non-equilibrium Green’s functions method for quantum transport. Silicon nanowires represent an interesting platform for spin devices. They are compatible with mature silicon technology and their intrinsic electronic properties can be controlled by modifying the diameter and length. Here we systematically study the spin transport properties for neutral nanowires and both n and p doping conditions. We find a substantial low bias magnetoresistance for the neutral case, which halves for an applied voltage of about 0.35 V and persists up to 1 V. Doping in general decreases the magnetoresistance, as soon as the conductance is no longer dominated by tunneling.
Tunneling magnetoresistance in Si nanowires
Montes Muñoz, Enrique
2016-11-09
We investigate the tunneling magnetoresistance of small diameter semiconducting Si nanowires attached to ferromagnetic Fe electrodes, using first principles density functional theory combined with the non-equilibrium Green\\'s functions method for quantum transport. Silicon nanowires represent an interesting platform for spin devices. They are compatible with mature silicon technology and their intrinsic electronic properties can be controlled by modifying the diameter and length. Here we systematically study the spin transport properties for neutral nanowires and both n and p doping conditions. We find a substantial low bias magnetoresistance for the neutral case, which halves for an applied voltage of about 0.35 V and persists up to 1 V. Doping in general decreases the magnetoresistance, as soon as the conductance is no longer dominated by tunneling.
Magnetoresistance stories of double perovskites
Indian Academy of Sciences (India)
Abhishek Nag; Sugata Ray
2015-06-01
Tunnelling magnetoresistance (TMR) in polycrystalline double perovskites has been an important research topic for more than a decade now, where the nature of the insulating tunnel barrier is the core issue of debate. Other than the nonmagnetic grain boundaries as conventional tunnel barriers, intragrain magnetic antiphase boundaries (APB) as well as magnetically frustrated grain surfaces have also been proposed to act as tunnel barriers in Sr2FeMoO6. In this review, the present state of the debate has been discussed briefly and how the physical state of the material can affect the magnetoresistance signal of double perovskites in many different ways has been pointed out.
Bipolaron Mechanism for Organic Magnetoresistance
Bobbert, P. A.; Nguyen, T. D.; van Oost, F. W. A.; Koopmans, B.; Wohlgenannt, M.
2007-11-01
We present a mechanism for the recently discovered magnetoresistance in disordered π-conjugated materials, based on hopping of polarons and bipolaron formation, in the presence of the random hyperfine fields of the hydrogen nuclei and an external magnetic field. Within a simple model we describe the magnetic field dependence of the bipolaron density. Monte Carlo simulations including on-site and longer-range Coulomb repulsion show how this leads to positive and negative magnetoresistance. Depending on the branching ratio between bipolaron formation or dissociation and hopping rates, two different line shapes in excellent agreement with experiment are obtained.
Biehler, Alexander; Kläui, Mathias; Fonin, Mikhail; König, Christian; Güntherodt, Gernot; Rüdiger, Ulrich
2007-01-01
We present a detailed study of the equilibrium magnetization configurations and their response to injected current pulses in microstructured CrO2 wire elements. Using magnetic force microscopy, we determine that the magnetic domain structure of CrO2 wires strongly depends on the wire geometry, in particular, on the wire width and the wire orientation with respect to the magnetocrystalline anisotropy axes. Depending on the wire geometry and the orientation of the initialization magnetic field ...
Ravelosona, Dafine
2016-10-01
One crucial breakthrough in spin electronics has recently been achieved regarding the possibility to move magnetic domain walls (DWs) in magnetic tracks using the sole action of an electrical current instead of a conventional magnetic field. Here, we will present our recent results of DW dynamics obtained in Ta-CoFeB-MgO nanodevices with perpendicular magnetic anisotropy (PMA), which are widely used in STT-RAM applications, and discuss the critical problems to be addressed for implementation into a memory device. Using NV center microscopy to map DW pinning along a magnetic wire, we will first show1 that Ta/CoFeB(1nm)/MgO structures exhibit a very low density of pinning defects with respect to others materials with PMA. Then, we will focus on the possibility to use Electric Field Effect to control domain wall motion with low power dissipation. We will demonstrate gate voltage modulation of DW dynamics using different approaches based on dielectrics, piezoelectrics and ionic liquid layers.
Khandkar, Mahendra D.; Stinchcombe, Robin; Barma, Mustansir
2017-01-01
We demonstrate the large-scale effects of the interplay between shape and hard-core interactions in a system with left- and right-pointing arrowheads on a line, with reorientation dynamics. This interplay leads to the formation of two types of domain walls, > (B ). The correlation length in the equilibrium state diverges exponentially with increasing arrowhead density, with an ordered state of like orientations arising in the limit. In this high-density limit, the A domain walls diffuse, while the B walls are static. In time, the approach to the ordered state is described by a coarsening process governed by the kinetics of domain-wall annihilation A +B →0 , quite different from the A +A →0 kinetics pertinent to the Glauber-Ising model. The survival probability of a finite set of walls is shown to decay exponentially with time, in contrast to the power-law decay known for A +A →0 . In the thermodynamic limit with a finite density of walls, coarsening as a function of time t is studied by simulation. While the number of walls falls as t-1/2, the fraction of persistent arrowheads decays as t-θ where θ is close to 1/4 , quite different from the Ising value. The global persistence too has θ =1/4 , as follows from a heuristic argument. In a generalization where the B walls diffuse slowly, θ varies continuously, increasing with increasing diffusion constant.
Institute of Scientific and Technical Information of China (English)
无
2006-01-01
The Ti-doped waveguide-type periodically poled LiNbO3 (PPLN) were fabricated and the dependence of domain wall velocity on an external field applied for domain inversion was investigated. The whole polarization reversal process was computer-controlled to regulate domain wall expansion at a feedback time shorter than 5 μs. The coercive voltage and several values of excess voltage were applied on 500 μm-thick wafers serially connected to a 1-MOhm external resistor which had an effect of the poling current reduction, i.e. the deceleration of domain wall expansion. The domain wall velocity is sensitive to the poling voltage, precisely speaking, to the excess voltage. The domain wall velocities were 28.70, 16.02 and 5.75 μm·s-1 under poling field of 23.5, 22.0 and 21.0 kV·mm-1, respectively. Moreover, average duty cycle of PPLN is about 49.93%.
Directory of Open Access Journals (Sweden)
Saeid Mokhtarian
2014-01-01
Full Text Available Despite extensive area of applications, simulation of complex wall bounded problems or any deformable boundary is still a challenge in a Dissipative Particle Dynamics simulation. This limitation is rooted in the soft force nature of DPD and the fact that we need to use an antipenetration model for escaped particles. In the present paper, we propose a new model of antipenetration which preserves the conservation of linear momentum on the boundaries and enables us to simulate complex and flexible boundaries. Finally by performing numerical simulations, we demonstrate the validity of our new model.