The Experts below are selected from a list of 360 Experts worldwide ranked by ideXlab platform
A Fert - One of the best experts on this subject based on the ideXlab platform.
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microwave excitations associated with a wavy Angular Dependence of the spin transfer torque model and experiments
Physical Review B, 2008Co-Authors: Olivier Boulle, F. Petroff, Vincent Cros, Julie Grollier, Luis Gustavo Pereira, C Deranlot, G Faini, J Barnaś, A FertAbstract:The spin transfer torque (STT) can lead to a steady precession of magnetization without any external applied field in magnetic spin valves where the magnetic layers have very different spin diffusion lengths. This effect is associated with a nonstandard Dependence of the STT, called ``wavy'' Angular Dependence of the STT (WAD-STT), predicted in the frame of diffusive models of spin transfer. In this paper, we present a complete experimental characterization of the magnetization dynamics in the presence of a WAD-STT. The results are compared to the prediction of the magnetization dynamics obtained by single domain magnetic simulations (macrospin approximation). The macrospin simulations reproduce well the main static and dynamical experimental features and suggest that the dynamical excitations experimentally observed are associated with a large angle out-of-plane precession mode. The present work validates the diffusive models of the spin transfer and underlines the role of the spin accumulation and the spin relaxation effects on the STT.
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shaped Angular Dependence of the spin transfer torque and microwave generation without magnetic field
Nature Physics, 2007Co-Authors: Olivier Boulle, F. Petroff, Vincent Cros, Julie Grollier, Luis Gustavo Pereira, C Deranlot, G Faini, Barna J Sacute, A FertAbstract:The generation of oscillations in the microwave frequency range is one of the most important applications expected from spintronics devices exploiting the spin-transfer phenomenon, which is the reorientation of the magnetization of a ferromagnetic domain by spin-polarized current. Here we report transport and microwave power measurements on specially designed nanopillars, for which a non-standard Angular Dependence of the spin-transfer torque is predicted by theoretical models. We observe a new kind of current-induced dynamics that is characterized by large angle precessions in the absence of any applied field. This is also predicted by simulations including a ‘wavy’ Angular Dependence of the torque. This type of nanopillar, which is able to generate microwave oscillations in zero applied magnetic field, could represent an interesting method for the implementation of spin-transfer oscillators. We also emphasize the theoretical implications of our results on the Angular Dependence of the torque.
Luis Gustavo Pereira - One of the best experts on this subject based on the ideXlab platform.
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microwave excitations associated with a wavy Angular Dependence of the spin transfer torque model and experiments
Physical Review B, 2008Co-Authors: Olivier Boulle, F. Petroff, Vincent Cros, Julie Grollier, Luis Gustavo Pereira, C Deranlot, G Faini, J Barnaś, A FertAbstract:The spin transfer torque (STT) can lead to a steady precession of magnetization without any external applied field in magnetic spin valves where the magnetic layers have very different spin diffusion lengths. This effect is associated with a nonstandard Dependence of the STT, called ``wavy'' Angular Dependence of the STT (WAD-STT), predicted in the frame of diffusive models of spin transfer. In this paper, we present a complete experimental characterization of the magnetization dynamics in the presence of a WAD-STT. The results are compared to the prediction of the magnetization dynamics obtained by single domain magnetic simulations (macrospin approximation). The macrospin simulations reproduce well the main static and dynamical experimental features and suggest that the dynamical excitations experimentally observed are associated with a large angle out-of-plane precession mode. The present work validates the diffusive models of the spin transfer and underlines the role of the spin accumulation and the spin relaxation effects on the STT.
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shaped Angular Dependence of the spin transfer torque and microwave generation without magnetic field
Nature Physics, 2007Co-Authors: Olivier Boulle, F. Petroff, Vincent Cros, Julie Grollier, Luis Gustavo Pereira, C Deranlot, G Faini, Barna J Sacute, A FertAbstract:The generation of oscillations in the microwave frequency range is one of the most important applications expected from spintronics devices exploiting the spin-transfer phenomenon, which is the reorientation of the magnetization of a ferromagnetic domain by spin-polarized current. Here we report transport and microwave power measurements on specially designed nanopillars, for which a non-standard Angular Dependence of the spin-transfer torque is predicted by theoretical models. We observe a new kind of current-induced dynamics that is characterized by large angle precessions in the absence of any applied field. This is also predicted by simulations including a ‘wavy’ Angular Dependence of the torque. This type of nanopillar, which is able to generate microwave oscillations in zero applied magnetic field, could represent an interesting method for the implementation of spin-transfer oscillators. We also emphasize the theoretical implications of our results on the Angular Dependence of the torque.
Bernhard H Schlegel - One of the best experts on this subject based on the ideXlab platform.
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Angular Dependence of strong field sequential double ionization for neon and acetylene simulated with time dependent configuration interaction using cis and cisd ip
Journal of Chemical Physics, 2020Co-Authors: Mi Kyung Lee, Bernhard H SchlegelAbstract:Strong field ionization is fundamentally important for attosecond spectroscopy and coherence control. However, the modeling beyond the single active electron approximation is still difficult. Time-dependent configuration interaction with singly excited configurations and a complex absorbing potential (TDCIS-CAP), can be used to simulate single and double ionization by intense laser fields. When the monocation does not have degenerate states, TDCIS-CAP starting from a Hartree–Fock calculation of the cation is suitable for simulating the second ionization step. When the monocation has two or more degenerate states, the simulations should treat these degenerate states equivalently. CISD-IP (single and double excitation configuration interaction with ionization) can be used to treat degenerate states of the cation on an equal footing by representing the cation wavefunctions with ionizing single (1 hole) and double (2 holes/1 particle) excitations from the neutral molecule. Since CISD-IP includes single excitations for each of the monocation states, time dependent CISD-IP with a complex absorbing potential (TDCISDIP-CAP) can also be used to simulate ionization to the dications states. In this work, TDCIS-CAP and TDCISDIP-CAP have been used to simulate the Angular Dependence of ionization of the neon cation and acetylene cation. In both cases, the second electron is ionized predominantly from an orbital perpendicular to the orbital involved in the first ionization. The TDCISDIP-CAP simulations show some features involving interactions between the monocation states that are not seen in the TDCIS-CAP simulations.Strong field ionization is fundamentally important for attosecond spectroscopy and coherence control. However, the modeling beyond the single active electron approximation is still difficult. Time-dependent configuration interaction with singly excited configurations and a complex absorbing potential (TDCIS-CAP), can be used to simulate single and double ionization by intense laser fields. When the monocation does not have degenerate states, TDCIS-CAP starting from a Hartree–Fock calculation of the cation is suitable for simulating the second ionization step. When the monocation has two or more degenerate states, the simulations should treat these degenerate states equivalently. CISD-IP (single and double excitation configuration interaction with ionization) can be used to treat degenerate states of the cation on an equal footing by representing the cation wavefunctions with ionizing single (1 hole) and double (2 holes/1 particle) excitations from the neutral molecule. Since CISD-IP includes single excita...
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Angular Dependence of strong field ionization of haloacetylenes hccx x f cl br i using time dependent configuration interaction with an absorbing potential
Journal of Physical Chemistry C, 2018Co-Authors: Paul Hoerner, Bernhard H SchlegelAbstract:Strong field ionization of haloacetylenes was simulated by time-dependent configuration interaction using all single excitations and a complex absorbing potential. The Angular Dependence of ionization for HCCX was mapped with static electric fields in the range 0.01–0.06 atomic units and compared with the results for CH3X. HCCF ionizes primarily from the CC π orbital. HCCX (X = Cl, Br, I) compounds show increasing amounts of ionization from the halogen π-type lone pair orbitals and have a node perpendicular to the molecular axis. These shapes can be understood in terms of the energies and interactions of the halogen π-type lone pairs with the π orbitals of the CC triple bond.
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Angular Dependence of ionization by circularly polarized light calculated with time dependent configuration interaction with an absorbing potential
Journal of Physical Chemistry A, 2017Co-Authors: Paul Hoerner, Bernhard H SchlegelAbstract:The Angular Dependence of ionization by linear and circularly polarized light has been examined for N2, NH3, H2O, CO2, CH2O, pyrazine, methyloxirane, and vinyloxirane. Time-dependent configuration interaction with single excitations and a complex absorbing potential was used to simulate ionization by a seven cycle 800 nm cosine squared pulse with intensities ranging from 0.56 × 1014 to 5.05 × 1014 W cm–2. The shapes of the ionization yield for linearly polarized light can be understood primarily in terms of the nodal structure of the highest occupied orbitals. Depending on the orbital energies, ionization from lower-lying orbitals may also make significant contributions to the shapes. The shapes of the ionization yield for circularly polarized light can be readily explained in terms of the shapes for linearly polarized light. Averaging the results for linear polarization over orientations perpendicular to the direction of propagation yields shapes that are in very good agreement with direct calculations o...
Olivier Boulle - One of the best experts on this subject based on the ideXlab platform.
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microwave excitations associated with a wavy Angular Dependence of the spin transfer torque model and experiments
Physical Review B, 2008Co-Authors: Olivier Boulle, F. Petroff, Vincent Cros, Julie Grollier, Luis Gustavo Pereira, C Deranlot, G Faini, J Barnaś, A FertAbstract:The spin transfer torque (STT) can lead to a steady precession of magnetization without any external applied field in magnetic spin valves where the magnetic layers have very different spin diffusion lengths. This effect is associated with a nonstandard Dependence of the STT, called ``wavy'' Angular Dependence of the STT (WAD-STT), predicted in the frame of diffusive models of spin transfer. In this paper, we present a complete experimental characterization of the magnetization dynamics in the presence of a WAD-STT. The results are compared to the prediction of the magnetization dynamics obtained by single domain magnetic simulations (macrospin approximation). The macrospin simulations reproduce well the main static and dynamical experimental features and suggest that the dynamical excitations experimentally observed are associated with a large angle out-of-plane precession mode. The present work validates the diffusive models of the spin transfer and underlines the role of the spin accumulation and the spin relaxation effects on the STT.
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shaped Angular Dependence of the spin transfer torque and microwave generation without magnetic field
Nature Physics, 2007Co-Authors: Olivier Boulle, F. Petroff, Vincent Cros, Julie Grollier, Luis Gustavo Pereira, C Deranlot, G Faini, Barna J Sacute, A FertAbstract:The generation of oscillations in the microwave frequency range is one of the most important applications expected from spintronics devices exploiting the spin-transfer phenomenon, which is the reorientation of the magnetization of a ferromagnetic domain by spin-polarized current. Here we report transport and microwave power measurements on specially designed nanopillars, for which a non-standard Angular Dependence of the spin-transfer torque is predicted by theoretical models. We observe a new kind of current-induced dynamics that is characterized by large angle precessions in the absence of any applied field. This is also predicted by simulations including a ‘wavy’ Angular Dependence of the torque. This type of nanopillar, which is able to generate microwave oscillations in zero applied magnetic field, could represent an interesting method for the implementation of spin-transfer oscillators. We also emphasize the theoretical implications of our results on the Angular Dependence of the torque.
F. Petroff - One of the best experts on this subject based on the ideXlab platform.
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microwave excitations associated with a wavy Angular Dependence of the spin transfer torque model and experiments
Physical Review B, 2008Co-Authors: Olivier Boulle, F. Petroff, Vincent Cros, Julie Grollier, Luis Gustavo Pereira, C Deranlot, G Faini, J Barnaś, A FertAbstract:The spin transfer torque (STT) can lead to a steady precession of magnetization without any external applied field in magnetic spin valves where the magnetic layers have very different spin diffusion lengths. This effect is associated with a nonstandard Dependence of the STT, called ``wavy'' Angular Dependence of the STT (WAD-STT), predicted in the frame of diffusive models of spin transfer. In this paper, we present a complete experimental characterization of the magnetization dynamics in the presence of a WAD-STT. The results are compared to the prediction of the magnetization dynamics obtained by single domain magnetic simulations (macrospin approximation). The macrospin simulations reproduce well the main static and dynamical experimental features and suggest that the dynamical excitations experimentally observed are associated with a large angle out-of-plane precession mode. The present work validates the diffusive models of the spin transfer and underlines the role of the spin accumulation and the spin relaxation effects on the STT.
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shaped Angular Dependence of the spin transfer torque and microwave generation without magnetic field
Nature Physics, 2007Co-Authors: Olivier Boulle, F. Petroff, Vincent Cros, Julie Grollier, Luis Gustavo Pereira, C Deranlot, G Faini, Barna J Sacute, A FertAbstract:The generation of oscillations in the microwave frequency range is one of the most important applications expected from spintronics devices exploiting the spin-transfer phenomenon, which is the reorientation of the magnetization of a ferromagnetic domain by spin-polarized current. Here we report transport and microwave power measurements on specially designed nanopillars, for which a non-standard Angular Dependence of the spin-transfer torque is predicted by theoretical models. We observe a new kind of current-induced dynamics that is characterized by large angle precessions in the absence of any applied field. This is also predicted by simulations including a ‘wavy’ Angular Dependence of the torque. This type of nanopillar, which is able to generate microwave oscillations in zero applied magnetic field, could represent an interesting method for the implementation of spin-transfer oscillators. We also emphasize the theoretical implications of our results on the Angular Dependence of the torque.
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Angular Dependence of the tunnel magnetoresistance in transition-metal-based junctions
Physical Review B: Condensed Matter (1978-1997), 2001Co-Authors: Henri Jaffrès, D Lacour, F. Nguyen Van Dau, J. Briatico, F. Petroff, A. VaurèsAbstract:We have investigated the Angular behavior of the tunnel magnetoresistance ͑TMR͒ in transition-metal-based junctions using the low-field susceptibility of the crossed magnetic configuration. The noncollinear arrangement , stabilized by combining step anisotropy and interfacial exchange-bias coupling, is shown to be of a particular interest for an accurate analysis of the Angular Dependence of the TMR. We show that the intrinsic tunnel processes are reflected on a linear behavior of the conductivity giving a more complex form for the resistance, as expected by the model of Slonczewski. The more intuitive ''high-field'' saturating regime deviates the hard layer from its nominal pinning direction and consequently is shown to be less adapted for the experimental study of the intrinsic Angular response of the TMR.