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Articles 31 - 60 of 73
Full-Text Articles in Physics
Proposal To Determine The Fermi-Surface Topology Of A Doped Iron-Based Superconductor Using Bulk-Sensitive Fourier-Transform Compton Scattering, Yung Wang, Hsin Lin, B. Barbiellini, P. Mijnarends, S. Kaprzyk, R. Markiewicz, A. Bansil
Proposal To Determine The Fermi-Surface Topology Of A Doped Iron-Based Superconductor Using Bulk-Sensitive Fourier-Transform Compton Scattering, Yung Wang, Hsin Lin, B. Barbiellini, P. Mijnarends, S. Kaprzyk, R. Markiewicz, A. Bansil
Hsin Lin
We have carried out first-principles calculations of the Compton scattering spectra to demonstrate that the filling of the hole Fermi surface in LaO₁₋ₓFₓFeAs produces a distinct signature in the Fourier-transformed Compton spectrum when the momentum transfer vector lies along the [100] direction. We thus show how the critical concentration xc
Origin Of The High-Energy Kink In The Photoemission Spectrum Of The High-Temperature Superconductor Bi₂Sr₂Cacu₂O₈, Susmita Basak, Tanmoy Das, Hsin Lin, J. Nieminen, M. Lindroos, R. Markiewicz, A. Bansil
Origin Of The High-Energy Kink In The Photoemission Spectrum Of The High-Temperature Superconductor Bi₂Sr₂Cacu₂O₈, Susmita Basak, Tanmoy Das, Hsin Lin, J. Nieminen, M. Lindroos, R. Markiewicz, A. Bansil
Hsin Lin
The high-energy kink or the waterfall effect seen in the photoemission spectra of cuprates is suggestive of the coupling of quasiparticles to a high-energy bosonic mode with implications for the mechanism of superconductivity. Recent experiments, however, indicate that this effect may be an artifact produced entirely by matrix element effects, i.e., by the way the photoemitted electron couples to incident photons in the emission process. In order to address this issue directly, we have carried out realistic computations of the photointensity in Bi₂Sr₂CaCu₂O₈ where the effects of the matrix element are included together with those of the corrections to the …
A Multi-Channel, Multi-Mode Biopotential Measurment Device, Thushara Perera, Boxiang Liu, '14
A Multi-Channel, Multi-Mode Biopotential Measurment Device, Thushara Perera, Boxiang Liu, '14
Thushara A. Perera
No abstract provided.
Dry Friction Due To Adsorbed Molecules, C. Daly, J. Zhang, J. Sokoloff
Dry Friction Due To Adsorbed Molecules, C. Daly, J. Zhang, J. Sokoloff
Christopher Daly
Using an adiabatic approximation method, which searches for Tomlinson model-like instabilities for a simple but still realistic model for two crystalline surfaces in the extremely light contact limit, with mobile molecules present at the interface, sliding relative to each other, we are able to account for the virtually universal occurrence of "dry friction." The model makes important predictions for the dependence of friction on the strength of the interaction of each surface with the mobile molecules.
A Novel Direct Method Of Fermi Surface Determination Using Constant Initial Energy Angle-Scanned Photoemission Spectroscopy, M. Lindroos, A. Bansil
A Novel Direct Method Of Fermi Surface Determination Using Constant Initial Energy Angle-Scanned Photoemission Spectroscopy, M. Lindroos, A. Bansil
Arun Bansil
We show that a constant initial energy, angle-scanned (CIE-AS) photoemission spectrum for emission from the Fermi energy (EF) contains Fermi surface (FS) signatures which originate from density of states type indirect transitions. Such previously unrecognized FS features in a CIE-AS spectrum would provide a robust and straightforward means of determining Fermi surfaces. Furthermore, the associated photointensity should yield a new window on k⊥, dispersion related issues in materials. Extensive simulations of CIE-AS spectra from low index faces of Cu are presented within the framework of the one-step photoemission model in order to delineate the nature of these new spectral features.
X-Ray Absorption Near-Edge Spectra Of Overdoped La₂₋ₓsrₓcuo₄ High-T(C) Superconductors, Towfiq Ahmed, Tanmoy Das, J. Kas, B. Barbiellini, Fernando Vila, R. Markiewicz, A. Bansil, J. Rehr
X-Ray Absorption Near-Edge Spectra Of Overdoped La₂₋ₓsrₓcuo₄ High-T(C) Superconductors, Towfiq Ahmed, Tanmoy Das, J. Kas, B. Barbiellini, Fernando Vila, R. Markiewicz, A. Bansil, J. Rehr
Arun Bansil
We present results for realistic modeling of the x-ray absorption near edge structure (XANES) of the overdoped high-Tc superconductor La₂₋ₓSrₓCuO₄ in the hole doping range x = 0.20 - 0.30. Our computations are based on a real-space Green's function approach in which strong-correlation effects are taken into account in terms of a doping-dependent self-energy. The predicted O K-edge XANES is found to be in good accord with the corresponding experimental results in this overdoped regime. We find that the low energy spectra are dominated by the contribution of O atoms in the cuprate planes, with little contribution from apical O …
Angle-Resolved Photoemission-Study Of (100), (110), And (111) Surfaces Of Cu0.9a10.1: Bulk And Surface Electronic-Structure Of The Alloy, H. Asonen, M. Lindroos, M. Pessa, P. Prasad, R. Rao, A. Bansil
Angle-Resolved Photoemission-Study Of (100), (110), And (111) Surfaces Of Cu0.9a10.1: Bulk And Surface Electronic-Structure Of The Alloy, H. Asonen, M. Lindroos, M. Pessa, P. Prasad, R. Rao, A. Bansil
Arun Bansil
We present angle-resolved photoemission spectra from the low-index faces of CuAl single crystals using 16.85- and 21.22-eV radiation, together with the computed bulk electronic structure of the alloy within the framework of the muffin-tin coherent-potential approximation (CPA). The d-band complex of Cu is found to suffer shifts of less than 0.1 eV on alloying, whereas the states of s-p symmetry are lowered in energy by as much as on the order of 1 eV. The dispersion curve of the uppermost valence band is measured and with the extrapolation of this curve to the Fermi energy (EF), the Fermi-surface radii along …
Coherent-Potential And Average T-Matrix Approximations For Disordered Muffin-Tin Alloys: 1. Formalism, A. Bansil
Arun Bansil
The average density of states 〈ρ(E)〉 and the component charge density associated with an A(B) atom in the alloy, 〈ρA(B)(E)〉, are discussed for the disordered alloy AₓB₁₋ₓ within the framework of the muffintin Hamiltonian. A new version of the average t-matrix (ATA) is developed. The structure in the spectral density function, 〈ρ(k,E)〉, in the coherent-potential approximation (or the new ATA) is seen to result from not only the Bloch-type states in the medium of coherent-potential effective atoms tCP (or the average t-atoms 〈t〉) but also from non-Bloch-type impurity levels arising when a single A or B atom …
Multiple-Scattering Theory Of Itinerant Electron Magnetism In Random Muffin-Tin Alloys, S. Kaprzyk, A. Bansil
Multiple-Scattering Theory Of Itinerant Electron Magnetism In Random Muffin-Tin Alloys, S. Kaprzyk, A. Bansil
Arun Bansil
We discuss the equilibrium electronic structure of a random binary alloy within the framework of a spin-dependent muffin-tin Hamiltonian. The disorder is treated on the basis of the single-site approximations (SSA), especially the average t-matrix and the coherent potential approximations. The local-spin-density (LSD) functional approach is employed to relate the electron and the spin densities with the atomic potentials, thus providing a fully self-consistent description of the ground-state properties of the random alloy. By using the atomic magnetic moments as expansion parameters, a Stoner-type linearized form of the full SSA-LSD formalism is developed. This analysis yields insights into the nature …
Induced Superconductivity In Noncuprate Layers Of The Bi₂Sr₂Cacu₂O₈+Δ High-Temperature Superconductor: Modeling Of Scanning Tunneling Spectra, Ilpo Suominen, Jouko Nieminen, R. Markiewicz, A. Bansil
Induced Superconductivity In Noncuprate Layers Of The Bi₂Sr₂Cacu₂O₈+Δ High-Temperature Superconductor: Modeling Of Scanning Tunneling Spectra, Ilpo Suominen, Jouko Nieminen, R. Markiewicz, A. Bansil
Arun Bansil
We analyze how the coherence peaks observed in scanning tunneling spectroscopy (STS) of cuprate high-temperature superconductors are transferred from the cuprate layer to the oxide layers adjacent to the STS microscope tip. For this purpose, we have carried out a realistic multiband calculation for the superconducting state of Bi₂Sr₂CaCu₂O₈₊δ (Bi2212) assuming a short-range d-wave pairing interaction confined to the nearest-neighbor Cu dₓ2₋y2 orbitals. The resulting anomalous matrix elements of the Green’s function allow us to monitor how pairing is then induced not only within the cuprate bilayer but also within and across other layers and …
Application Of Coherent-Potential Approximation To Disordered Muffin-Tin Alloys, A. Bansil
Application Of Coherent-Potential Approximation To Disordered Muffin-Tin Alloys, A. Bansil
Arun Bansil
I report implementation of the coherent-potential approximation for obtaining the electronic density of states and component charge densities in disordered muffin-tin alloys. Illustrative results for CuₓNi₁₋ₓ are presented. The extent to which the self-consistency in treating disorder influences the electronic spectrum is considered.
Reconstructing The Bulk Fermi Surface And Superconducting Gap Properties From Neutron Scattering Experiments, Tanmoy Das, R. Markiewicz, A. Bansil
Reconstructing The Bulk Fermi Surface And Superconducting Gap Properties From Neutron Scattering Experiments, Tanmoy Das, R. Markiewicz, A. Bansil
Arun Bansil
We develop an analytical tool to extract bulk electronic properties of unconventional superconductors from inelastic neutron scattering spectra. We show that the upward and downward branches of the spin excitation spectra have distinct origins, with the upper branch representing a gapped spin-wave dispersion and the lower branch associated with Bogoliubov quasiparticle scattering on the Fermi surface. Combined, they produce an "hourglass" dispersion with 45 degrees rotation of the spectrum, as found experimentally. The downward dispersion can be inverted to reveal the Fermi momentum dispersion of the single-particle spectrum as well as the corresponding superconducting (SC) gap function, analogously to the …
Topological Electronic Structure In Half-Heusler Topological Insulators, W. Al-Sawai, Hsin Lin, R. Markiewicz, L. Wray, Y. Xia, S. Xu, M. Hasan, A. Bansil
Topological Electronic Structure In Half-Heusler Topological Insulators, W. Al-Sawai, Hsin Lin, R. Markiewicz, L. Wray, Y. Xia, S. Xu, M. Hasan, A. Bansil
Arun Bansil
We have investigated band structures of a series of 28 ternary half-Heusler compounds MM'X of MgAgAs type, where M=(Lu, La, Sc, Y) and M'X=(PtBi, AuPb, PdBi, PtSb, AuSn, NiBi, PdSb). Our results show that the Z₂ topological order is due to a single band inversion at the Γ point. In native states, these half-Heusler compounds are identified as being topologically nontrivial semimetals, or nontrivial metals, or trivial insulators, which can be turned into insulating thin films on suitable substrates. Our analysis reveals a straightforward relationship which connects the band inversion strength (extent of deviation from the critical point) to the …
Energy Dependence Of Experimental Be Compton Profiles, S. Huotari, K. Hamalainen, S. Manninen, S. Kaprzyk, A. Bansil, W. Caliebe, T. Buslaps, V. Honkimaki, P. Suortti
Energy Dependence Of Experimental Be Compton Profiles, S. Huotari, K. Hamalainen, S. Manninen, S. Kaprzyk, A. Bansil, W. Caliebe, T. Buslaps, V. Honkimaki, P. Suortti
Arun Bansil
High-resolution Compton scattering measurements on Be single crystals along three main crystallographic directions ([10.0], [11.0], and [00.1]) have been carried out using incident photon energies of 10, 29, and 56 keV to study the energy dependence of the scattering cross:section. The experimental Compton profiles are in good agreement with theoretical profiles employing the local density approximation-based band theory framework. Extensive comparisons between the computed and measured profiles, their first derivatives, and anisotropies defined as differences between various pairs of profiles show an excellent level of accord. The details related to the Fermi surface are clearly seen in the experimental Compton …
One-Band Tight-Binding Model Parametrization Of The High-Tc Cuprates Including The Effect Of Kz Dispersion, R. Markiewicz, S. Sahrakorpi, M. Lindroos, Hsin Lin, A. Bansil
One-Band Tight-Binding Model Parametrization Of The High-Tc Cuprates Including The Effect Of Kz Dispersion, R. Markiewicz, S. Sahrakorpi, M. Lindroos, Hsin Lin, A. Bansil
Arun Bansil
We discuss the effects of interlayer hopping and the resulting kz dispersion in the cuprates within the framework of the one-band tight-binding model Hamiltonian. Specific forms of the dispersion relations in terms of the in-plane hopping parameters t, t′, t″, and t‴ and the effective interlayer hopping tz in La₂₋ₓSrₓCuO₄ (LSCO) and Nd₂₋ₓCeₓCuO₄ (NCCO) and the added intracell hopping tbi between the CuO₂ bilayers in Bi₂Sr₂CaCu₂O₈ (Bi2212) are presented. The values of the “bare” parameters are obtained via fits with the first-principles local-density-approximation- (LDA-) based band structures in LSCO, NCCO, and Bi2212. The corresponding “dressed” parameter sets which account for …
Fermi Surface Evolution And Collapse Of The Mott Pseudogap In Nd2-Xcexcuo4±Δ, C. Kusko, R. Markiewicz, M. Lindroos, A. Bansil
Fermi Surface Evolution And Collapse Of The Mott Pseudogap In Nd2-Xcexcuo4±Δ, C. Kusko, R. Markiewicz, M. Lindroos, A. Bansil
Arun Bansil
Fermi surface (FS) maps and spectral intensities obtained recently in Nd₂₋ₓCeₓCuO₄±δ via high resolution ARPES measurements are analyzed using mean-field Hartree Fock and self-consistent renormalization computations within the framework of the one-band t-t′-t″-U Hubbard model Hamiltonian. We show that the remarkable observed crossover of the FS from small to large sheets reflects a reduction in the value of the effective Hubbard U with increasing electron doping and the collapse of the correlation induced Mott pseudogap just above optimal doping.
Compton Profiles For Polycrystalline Cuxni1-X Alloys: Theory And Experiment, R. Benedek, R. Prasad, S. Manninen, B. Sharma, A. Bansil, P. Mijnarends
Compton Profiles For Polycrystalline Cuxni1-X Alloys: Theory And Experiment, R. Benedek, R. Prasad, S. Manninen, B. Sharma, A. Bansil, P. Mijnarends
Arun Bansil
We present experimental and theoretical Compton profiles, J(q), for a series of CuₓNi₁₋ₓ alloys. This is the first comprehensive study of Compton profiles in an alloy system. The experiments were carried out using 60-keV γ rays on five polycrystalline alloy samples with Cu concentrations x=0.40,0.50,0.55,0.60,0.65 and on pure Cu and pure Ni. Our computations of J(q) are based on the Korringa-Kohn-Rostoker coherent-potential approximation scheme for treating the average electronic spectrum of the alloy. The theory reproduces the main features of the observed Compton profiles. The experimental Compton profiles show a nearly linear dependence on concentration while the theoretically predicted Compton …
Bistability In A Simple Fluid Network Due To Viscosity Contrast, John Geddes, Brian Storey, David Gardner, Russell Carr
Bistability In A Simple Fluid Network Due To Viscosity Contrast, John Geddes, Brian Storey, David Gardner, Russell Carr
Brian Storey
We study the existence of multiple equilibrium states in a simple fluid network using Newtonian fluids and laminar flow. We demonstrate theoretically the presence of hysteresis and bistability, and we confirm these predictions in an experiment using two miscible fluids of different viscosity—sucrose solution and water. Possible applications include blood flow, microfluidics, and other network flows governed by similar principles.
Electrically Controlled Exchange Bias For Spintronic Applications, Christian Binek, A. Hochstrat, X. Chen, P. Borisov, W. Kleeman, B. Doudin
Electrically Controlled Exchange Bias For Spintronic Applications, Christian Binek, A. Hochstrat, X. Chen, P. Borisov, W. Kleeman, B. Doudin
Christian Binek
Exchange coupling between a magnetoelectric (111)-oriented Cr2O3 single crystal and a CoPt multilayer with perpendicular anisotropy exhibits an exchange bias field proportional to the applied axial electric field. Extrapolation from bulk to thin film magnetoelectric pinning system suggests promising spintronic applications due to coupling between the electric field-controlled magnetization and the magnetization of a neighbor ferromagnetic layer. Pure voltage control of magnetic configurations of tunneling magnetoresistance spin valves is an attractive alternative to current-induced magnetization switching. ©2005 American Institute of Physics
Freezing Field Dependance Of The Exchange Bias In Uniaxial Fef2-Copt Heterosystems With Perpendicular Anisotropy, Christian Binek
Freezing Field Dependance Of The Exchange Bias In Uniaxial Fef2-Copt Heterosystems With Perpendicular Anisotropy, Christian Binek
Christian Binek
The exchange bias effect is measured for the first time in FeF2–CoPt heterosystems with perpendicular anisotropy. The exchange previous field exhibits a strong dependence on the axial previous freezing field. This behavior is explained in terms of the microscopic spin structure at the interface, which is established on cooling to below TN. We calculate the dependence of the spin structure on the previous freezing field within the framework of an Ising model. It takes into account the Zeeman energy as well as an antiferromagnetic exchange coupling between the adjacent layers at the interface.
Isothermal Low-Field Tuning Of Exchange Bias In Epitaxial Fe/Cr2o3/Fe, S. Sahoo, T. Mukherjee, K. Belashchenko, Christian Binek
Isothermal Low-Field Tuning Of Exchange Bias In Epitaxial Fe/Cr2o3/Fe, S. Sahoo, T. Mukherjee, K. Belashchenko, Christian Binek
Christian Binek
Moderate dc magnetic fields of less than 1 T allow tuning the exchange bias in an epitaxially grown Fe 10 nm/Cr2O3 2.7 nm/Fe 10 nm trilayer between negative and positive bias fields. Remarkably, this tunable exchange bias is observed at least up to 395 K which exceeds the Néel temperature of bulk Cr2O3 (307 K). The presence of spontaneous exchange bias and the absence of training effects at room temperature suggest the existence of stable interface moments independent of antiferromagnetic long range order in Cr2O3. Furthermore, the coercivity remains constant, independent of the exchange bias field. In contrast, large training …
Temperature Dependence Of The Training Effect In Exchange Coupled Ferromagnetic Bilayers, S. Polisetty, Sarbeswar Sahoo, A. Berger, Christian Binek
Temperature Dependence Of The Training Effect In Exchange Coupled Ferromagnetic Bilayers, S. Polisetty, Sarbeswar Sahoo, A. Berger, Christian Binek
Christian Binek
The temperature dependence of the training effect is studied in an exchange coupled thin-film bilayer composed of a hard ferromagnetic pinning (CoPtCrB) layer in proximity of a soft ferromagnetic pinned (CoCr) layer. Interlayer exchange shifts the hysteresis loops of the soft layer along the magnetic-field axis. This shift is quantified by the bias field in far reaching analogy to the exchange bias field of conventional antiferromagnetic/ferromagnetic heterostructures. A ferromagnetic domain state induced in the hard layer experiences aging very similar to the training behavior of the antiferromagnetic domain state in conventional exchange bias systems. Training originates from changes in the …
Dilution-Induced Enhancement Of The Blocking Temperature In Exchange-Bias Heterosystems, Xi Chen, Christian Binek, A. Hochstrat, W. Kleeman
Dilution-Induced Enhancement Of The Blocking Temperature In Exchange-Bias Heterosystems, Xi Chen, Christian Binek, A. Hochstrat, W. Kleeman
Christian Binek
The temperature dependence of the exchange bias field is investigated by superconducting quantum interference device magnetometry in Fe1-xZnxF2(110)/Fe14 nm/Ag35 nm, x=0.4. Its blocking temperature exhibits a significant enhancement with respect to the global ordering temperature TN=46.9 K, of the bulk antiferromagnet Fe0.6Zn0.4F2. The enhancement is attributed to fluctuations of the diamagnetic dilution which creates clusters on all length scales having a Zn dilution of 0<~x<~1. While the infinite clusters give rise to the well-known Griffiths phase, finite clusters also provoke a local enhancement of the exchange bias. The temperature dependence of the integral exchange bias effect is modeled by averaging all local contributions of the antiferromagnetic surface magnetization which exhibit a surface critical behavior.
Magnetic Relaxation Phenomena In The Superspin-Glass System [Co80Fe20/Al2O3]10, S. Sahoo, O. Petracic, Christian Binek, W. Kleemann, J. B. Sousa, S. Cardoso, P. P. Freitas
Magnetic Relaxation Phenomena In The Superspin-Glass System [Co80Fe20/Al2O3]10, S. Sahoo, O. Petracic, Christian Binek, W. Kleemann, J. B. Sousa, S. Cardoso, P. P. Freitas
Christian Binek
Relaxation and temperature cycles of thermoremanent magnetization, MTRM, in the superspin-glass phase of [Co80Fe20 (0.9 nm)/Al2O3 (3 nm)] 10 have been investigated. The relaxation of MTRM exhibits ageing phenomena. In negative temperature cycles for temperature steps larger than 1 K the magnetic state is retrieved (memory effect) on returning to the measurement temperature. This property is independent of the application of a field step during intermediate cooling. In positive temperature cycles the relaxation is suppressed after temporary heating. The observations are discussed in the light of both the droplet and the hierarchical picture.
Metamagnetic Domains And Dynamic Fluctuations In Febr2, O. Petracic, Christian Binek, W. Kleeman
Metamagnetic Domains And Dynamic Fluctuations In Febr2, O. Petracic, Christian Binek, W. Kleeman
Christian Binek
The mixed phase and the regime of non-critical fluctuations of the magnetic phase diagram of FeBr2 is investigated by SQUID susceptometry and light diffraction techniques. The experiments seem to evidence instability of the tricritical point as conjectured recently. The observation of stripe domains and light diffraction below and above Tm = 4.6 K and the virtual continuation of the phase transition line to above Tm are in agreement with the occurrence of a critical endpoint at Tm and of a bicritical endpoint at T > Tm. ©1997 American Institute of Physics.
Quenching Of The Exchange Bias Training In Fe/Cr2o3/Fe Trilayer, S. Sahoo, Christian Binek
Quenching Of The Exchange Bias Training In Fe/Cr2o3/Fe Trilayer, S. Sahoo, Christian Binek
Christian Binek
Exchange bias (EB) and its associated training effects are studied in an epitaxial Fe(10 nm)/Cr2O3(2.7 nm)/Fe(10 nm) trilayer heterostructure grown by molecular beam epitaxy. The EB decreases linearly with increasing temperature from T = 5 K to T = 50 K. It changes sign and becomes positive within 50 K < T < 200 K, finally changing back to regular EB for T<200K up to the highest measured temperature of T = 395 K. Remarkably, the latter is far above the bulk Néel temperature TN = 307 K. EB training effects occur only at 5 K < T < 50 K. We show …
Magnetic States Of Discontinuous Co80fe20al2o3 Multilayers, Christian Binek
Magnetic States Of Discontinuous Co80fe20al2o3 Multilayers, Christian Binek
Christian Binek
Discontinuous metal–insulator multilayers [Co80Fe20(t)/Al2O3(3 nm)]n were studied by SQUID magnetometry and AC susceptometry. CoFe forms ferromagnetic particles in the Al2O3 matrix. In this paper, we focus on the field dependence of the AC susceptibility of samples with t=1.3 nm. We find strong evidence for transitions from a superpara- to a superferromagnetic and, finally, to a reentrant superspin glass previous state.
Nonadiabatic Heat-Capacity Measurements Using A Superconducting Quantum Interference Device Magnetometer, A.I. Kharkovski, Christian Binek, W. Kleeman
Nonadiabatic Heat-Capacity Measurements Using A Superconducting Quantum Interference Device Magnetometer, A.I. Kharkovski, Christian Binek, W. Kleeman
Christian Binek
Nonadiabatic measurements of the heat capacity involving sample-inherent thermometry are proposed. The method is realized with superconducting quantum interference device magnetometry and applied to FeBr2 single crystals by using the magnetization for both thermometry and relaxation calorimetry. When heating with a step pulse of laser light, the magnetization relaxes on a characteristic time scale Ί = RC, where C is the heat capacity and R is the heat resistance between the sample and the bath. R is independently determined from the temperature dependence of the magnetic moment measured with and without stationary light irradiation. ©2000 American Institute of Physics.
Robust Isothermal Electric Control Of Exchange Bias At Room Temperature, Xi He, Yi Wang, Christian Binek, Peter Dowben
Robust Isothermal Electric Control Of Exchange Bias At Room Temperature, Xi He, Yi Wang, Christian Binek, Peter Dowben
Christian Binek
Voltage-controlled spin electronics is crucial for continued progress in information technology. It aims at reduced power consumption, increased integration density and enhanced functionality where non-volatile memory is combined with highspeed logical processing. Promising spintronic device concepts use the electric control of interface and surface magnetization. From the combination of magnetometry, spin-polarized photoemission spectroscopy, symmetry arguments and first-principles calculations, we show that the (0001) surface of magnetoelectric Cr2O3 has a roughness-insensitive, electrically switchable magnetization. Using a ferromagnetic Pd/Co multilayer deposited on the (0001) surface of a Cr2O3 single crystal, we achieve reversible, room-temperature isothermal switching of the exchange-bias field between positive …
Domain Wall Relaxation, Creep, Sliding, And Switching In Superferromagnetic Discontinuous Co80Fe20/Al2O3 Multilayers, X. Chen, O. Sichelschmidt, W. Kleeman, Christian Binek, J.B. Sousa, S. Cardoso, P.P. Freitas
Domain Wall Relaxation, Creep, Sliding, And Switching In Superferromagnetic Discontinuous Co80Fe20/Al2O3 Multilayers, X. Chen, O. Sichelschmidt, W. Kleeman, Christian Binek, J.B. Sousa, S. Cardoso, P.P. Freitas
Christian Binek
The ac susceptibility of a superferromagnetic discontinuous multilayer [Co80Fe20(1.4 nm)/ Al2O3(3 nm)]10 is measured as a function of temperature, frequency, and field amplitude and compared to static and dynamic hysteresis loops. Its properties are successfully mapped onto the predicted [T. Nattermann, V. Pokrovsky, and V. M. Vinokur, Phys. Rev. Lett. 87, 197005 (2001).] dynamical phase transitions, which link the relaxation, creep, sliding, and switching regimes of pinned domain walls.