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Keywords = Landau-Lifshitz-Gilbert equation

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18 pages, 37584 KiB  
Article
Breather Bound States in a Parametrically Driven Magnetic Wire
by Camilo José Castro, Ignacio Ortega-Piwonka, Boris A. Malomed, Deterlino Urzagasti, Liliana Pedraja-Rejas, Pablo Díaz and David Laroze
Symmetry 2024, 16(12), 1565; https://doi.org/10.3390/sym16121565 - 22 Nov 2024
Viewed by 925
Abstract
We report the results of a systematic investigation of localized dynamical states in the model of a one-dimensional magnetic wire, which is based on the Landau–Lifshitz–Gilbert (LLG) equation. The dissipative term in the LLG equation is compensated by the parametric drive imposed by [...] Read more.
We report the results of a systematic investigation of localized dynamical states in the model of a one-dimensional magnetic wire, which is based on the Landau–Lifshitz–Gilbert (LLG) equation. The dissipative term in the LLG equation is compensated by the parametric drive imposed by the external AC magnetic field, which is uniformly applied perpendicular to the rectilinear wire. The existence and stability of the localized states is studied in the plane of the relevant control parameters, namely, the amplitude of the driving term and the detuning of its frequency from the parametric resonance. With the help of systematically performed simulations of the LLG equation, the existence and stability areas are identified in the parameter plane for several species of the localized states: stationary single- and two-soliton modes, single and double breathers, drifting double breathers with spontaneously broken inner symmetry, and multisoliton complexes. Multistability occurs in this system. The breathers emit radiation waves (which explains their drift caused by the spontaneous symmetry breaking, as it breaks the balance between the recoil from the waves emitted to left and right), while the multisoliton complexes exhibit cycles of periodic transitions between three-, five-, and seven-soliton configurations. Dynamical characteristics of the localized states are systematically calculated too. These include, in particular, the average velocity of the asymmetric drifting modes, and the largest Lyapunov exponent, whose negative and positive values imply that the intrinsic dynamics of the respective modes is regular or chaotic, respectively. Full article
(This article belongs to the Special Issue Nonlinear Science and Numerical Simulation with Symmetry)
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18 pages, 1082 KiB  
Article
Temporal High-Order Accurate Numerical Scheme for the Landau–Lifshitz–Gilbert Equation
by Jiayun He, Lei Yang and Jiajun Zhan
Mathematics 2024, 12(8), 1179; https://doi.org/10.3390/math12081179 - 15 Apr 2024
Cited by 1 | Viewed by 1211
Abstract
In this paper, a family of temporal high-order accurate numerical schemes for the Landau–Lifshitz–Gilbert (LLG) equation is proposed. The proposed schemes are developed utilizing the Gauss–Legendre quadrature method, enabling them to achieve arbitrary high-order time discretization. Furthermore, the geometrical properties of the LLG [...] Read more.
In this paper, a family of temporal high-order accurate numerical schemes for the Landau–Lifshitz–Gilbert (LLG) equation is proposed. The proposed schemes are developed utilizing the Gauss–Legendre quadrature method, enabling them to achieve arbitrary high-order time discretization. Furthermore, the geometrical properties of the LLG equation, such as the preservation of constant magnetization magnitude and the Lyapunov structure, are investigated based on the proposed discrete schemes. It is demonstrated that the magnetization magnitude remains constant with an error of (2p+3) order in time when utilizing a (2p+2)th-order discrete scheme. Additionally, the preservation of the Lyapunov structure is achieved with a second-order error in the temporal step size. Numerical experiments and simulations effectively verify the performance of our proposed algorithm and validate our theoretical analysis. Full article
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12 pages, 5576 KiB  
Article
Realization of Artificial Neurons and Synapses Based on STDP Designed by an MTJ Device
by Manman Wang, Yuhai Yuan and Yanfeng Jiang
Micromachines 2023, 14(10), 1820; https://doi.org/10.3390/mi14101820 - 23 Sep 2023
Cited by 2 | Viewed by 1712
Abstract
As the third-generation neural network, the spiking neural network (SNN) has become one of the most promising neuromorphic computing paradigms to mimic brain neural networks over the past decade. The SNN shows many advantages in performing classification and recognition tasks in the artificial [...] Read more.
As the third-generation neural network, the spiking neural network (SNN) has become one of the most promising neuromorphic computing paradigms to mimic brain neural networks over the past decade. The SNN shows many advantages in performing classification and recognition tasks in the artificial intelligence field. In the SNN, the communication between the pre-synapse neuron (PRE) and the post-synapse neuron (POST) is conducted by the synapse. The corresponding synaptic weights are dependent on both the spiking patterns of the PRE and the POST, which are updated by spike-timing-dependent plasticity (STDP) rules. The emergence and growing maturity of spintronic devices present a new approach for constructing the SNN. In the paper, a novel SNN is proposed, in which both the synapse and the neuron are mimicked with the spin transfer torque magnetic tunnel junction (STT-MTJ) device. The synaptic weight is presented by the conductance of the MTJ device. The mapping of the probabilistic spiking nature of the neuron to the stochastic switching behavior of the MTJ with thermal noise is presented based on the stochastic Landau–Lifshitz–Gilbert (LLG) equation. In this way, a simplified SNN is mimicked with the MTJ device. The function of the mimicked SNN is verified by a handwritten digit recognition task based on the MINIST database. Full article
(This article belongs to the Special Issue Artificial Intelligence for Micro/Nano Materials and Devices)
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13 pages, 2569 KiB  
Article
Towards Resonantly Enhanced Acoustic Phonon-Exchange Magnon Interactions at THz Frequencies
by Tudor-Gabriel Mocioi, Antonia Ghita and Vasily V. Temnov
Magnetochemistry 2023, 9(7), 184; https://doi.org/10.3390/magnetochemistry9070184 - 17 Jul 2023
Cited by 4 | Viewed by 2521
Abstract
Using valid experimental parameters, we quantify the magnitude of resonantly phonon-driven precession of exchange magnons in freestanding ferromagnetic nickel thin films on their thickness L. Analytical solutions of acoustically driven equations for magnon oscillators display a nonmonotonous dependence of the peak magnetization [...] Read more.
Using valid experimental parameters, we quantify the magnitude of resonantly phonon-driven precession of exchange magnons in freestanding ferromagnetic nickel thin films on their thickness L. Analytical solutions of acoustically driven equations for magnon oscillators display a nonmonotonous dependence of the peak magnetization precession on the film thickness. It is explained by different L-dependence of multiple prefactors entering in the expression for the total magnetization dynamics. Depending on the ratio of acoustic and magnetic (Gilbert) damping constants, the magnetization precession is shown to be amplified by a Q-factor of either the phonon or the magnon resonance. The increase in the phonon mode amplitude for thinner membranes is also found to be significant. Focusing on the magnetization dynamics excited by the two first acoustic eigenmodes with p=1 and p=2, we predict the optimum thicknesses of nickel membranes to achieve large amplitude magnetization precession at multi 100 GHz frequencies at reasonably low values of an external magnetic field. By extending the study to the case of Ni-Si bilayers, we show that these resonances are achievable at even higher frequencies, approaching the THz range. Full article
(This article belongs to the Special Issue State-of-the-Art Research in Magnetism in France)
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18 pages, 2688 KiB  
Article
Finite Element Approach for the Simulation of Modern MRAM Devices
by Simone Fiorentini, Nils Petter Jørstad, Johannes Ender, Roberto Lacerda de Orio, Siegfried Selberherr, Mario Bendra, Wolfgang Goes and Viktor Sverdlov
Micromachines 2023, 14(5), 898; https://doi.org/10.3390/mi14050898 - 22 Apr 2023
Cited by 10 | Viewed by 2274
Abstract
Because of their nonvolatile nature and simple structure, the interest in MRAM devices has been steadily growing in recent years. Reliable simulation tools, capable of handling complex geometries composed of multiple materials, provide valuable help in improving the design of MRAM cells. In [...] Read more.
Because of their nonvolatile nature and simple structure, the interest in MRAM devices has been steadily growing in recent years. Reliable simulation tools, capable of handling complex geometries composed of multiple materials, provide valuable help in improving the design of MRAM cells. In this work, we describe a solver based on the finite element implementation of the Landau–Lifshitz–Gilbert equation coupled to the spin and charge drift-diffusion formalism. The torque acting in all layers from different contributions is computed from a unified expression. In consequence of the versatility of the finite element implementation, the solver is applied to switching simulations of recently proposed structures based on spin-transfer torque, with a double reference layer or an elongated and composite free layer, and of a structure combining spin-transfer and spin-orbit torques. Full article
(This article belongs to the Special Issue Magnetic and Spin Devices, Volume II)
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27 pages, 1056 KiB  
Article
Microstructural Model of Magnetic and Deformation Behavior of Single Crystals and Polycrystals of Ferromagnetic Shape Memory Alloy
by Anatoli A. Rogovoy and Olga S. Stolbova
Magnetochemistry 2023, 9(2), 40; https://doi.org/10.3390/magnetochemistry9020040 - 20 Jan 2023
Cited by 3 | Viewed by 2038
Abstract
In this article, a microstructural model of the Heusler alloy with the shape memory effect caused by the application of an external magnetic field is constructed. The dynamics of the magnetization process are described using the Landau–Lifshitz–Gilbert equation. For the numerical implementation of [...] Read more.
In this article, a microstructural model of the Heusler alloy with the shape memory effect caused by the application of an external magnetic field is constructed. The dynamics of the magnetization process are described using the Landau–Lifshitz–Gilbert equation. For the numerical implementation of the model using the finite element method, the variational equations corresponding to the differential formulation of the magnetic problem are used. Such an approach makes it possible to reduce (weaken) the requirements for the smoothness of the sought solution. The problem of magnetization of single crystals of the Ni2MnGa alloy, which has a “herringbone”-type martensitic structure (a twinned variant of martensite), is considered. In each element of the twin, the magnetic domains with walls of a certain thickness are formed. The motion and interaction of these walls and the rotation of magnetization vector in the walls and domains under the action of the external differently directed magnetic fields are studied. These processes in the Heusler alloy are also accompanied by the detwinning process. A condition for the detwinning of a ferromagnetic shape memory alloy in a magnetic field is proposed, and the effect of the reorientation (detwinning) of martensitic variants forming a twin on the magnetization of the material and the occurrence of structural (detwinning) deformation in it are taken into account. First, the processes of magnetization and structural deformation in a single grain are considered at different angles between the anisotropy axes of twinned variants and the external magnetic field. For these cases, the magnetization curves are constructed, and the deformed states are identified. The model described such experimental facts as the detwinning process and the jump in magnetization on these curves as a result of this process. It was shown that the jump occurred at a certain magnitude of the strength of the applied external magnetic field and a certain direction of its action relative to the twinning system. Then, based on the obtained results, deformed states arising due to the detwinning process were determined for various (isotropic and texture-oriented) polycrystalline samples, and magnetization curves taking into account this process were constructed for these materials. Full article
(This article belongs to the Section Applications of Magnetism and Magnetic Materials)
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12 pages, 4089 KiB  
Article
Field-Driven Magnetic Phase Diagram and Vortex Stability in Fe Nanometric Square Prisms
by Mauricio Galvis, Fredy Mesa and Johans Restrepo
Nanomaterials 2022, 12(23), 4243; https://doi.org/10.3390/nano12234243 - 29 Nov 2022
Cited by 1 | Viewed by 2223
Abstract
In this work, we deal with the zero temperature hysteretic properties of iron (Fe) quadrangular nanoprisms and the size conditions underlying magnetic vortex states formation. Different aspect ratios of a square base prism of thickness t with free boundary conditions were [...] Read more.
In this work, we deal with the zero temperature hysteretic properties of iron (Fe) quadrangular nanoprisms and the size conditions underlying magnetic vortex states formation. Different aspect ratios of a square base prism of thickness t with free boundary conditions were considered in order to summarize our results in a proposal of a field-driven magnetic phase diagram where such vortex states are stable along the hysteresis loops. To do that, a Hamiltonian consisting of exchange, magnetostatic, Zeeman and cubic anisotropy energies was considered. The time dynamics at each magnetic field step was performed by solving the time-dependent Landau–Lifshitz–Gilbert differential equation. The micromagnetic simulations were performed using the Ubermag package based on the Object Oriented Micromagnetic Framework (OOMMF). Circular magnetic textures were also characterized by means of topological charge calculations. The aspect ratio dependencies of the coercive force, nucleation and annihilation fields are also analyzed. Computations agree with related experimental observations and other micromagnetic calculations. Full article
(This article belongs to the Topic Advances in Phase Change Materials)
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10 pages, 1174 KiB  
Article
Magnetic Interconnects Based on Composite Multiferroics
by Alexander Khitun
Micromachines 2022, 13(11), 1991; https://doi.org/10.3390/mi13111991 - 17 Nov 2022
Cited by 1 | Viewed by 1910
Abstract
The development of magnetic logic devices dictates a need for a novel type of interconnect for magnetic signal transmission. Fast signal damping is one of the problems which drastically differs from conventional electric technology. Here, we describe a magnetic interconnect based on a [...] Read more.
The development of magnetic logic devices dictates a need for a novel type of interconnect for magnetic signal transmission. Fast signal damping is one of the problems which drastically differs from conventional electric technology. Here, we describe a magnetic interconnect based on a composite multiferroic comprising piezoelectric and magnetostrictive materials. Internal signal amplification is the main reason for using multiferroic material, where a portion of energy can be transferred from electric to magnetic domains via stress-mediated coupling. The utilization of composite multiferroics consisting of piezoelectric and magnetostrictive materials offers flexibility for the separate adjustment of electric and magnetic characteristics. The structure of the proposed interconnect resembles a parallel plate capacitor filled with a piezoelectric, where one of the plates comprises a magnetoelastic material. An electric field applied across the plates of the capacitor produces stress, which, in turn, affects the magnetic properties of the magnetostrictive material. The charging of the capacitor from one edge results in the charge diffusion accompanied by the magnetization change in the magnetostrictive layer. This enables the amplitude of the magnetic signal to remain constant during the propagation. The operation of the proposed interconnects is illustrated by numerical modeling. The model is based on the Landau–Lifshitz–Gilbert equation with the electric field-dependent anisotropy term included. A variety of magnetic logic devices and architectures can benefit from the proposed interconnects, as they provide reliable and low-energy-consuming data transmission. According to the estimates, the group velocity of magnetic signals may be up to 105 m/s with energy dissipation less than 10−18 J per bit per 100 nm. The physical limits and practical challenges of the proposed approach are also discussed. Full article
(This article belongs to the Special Issue Magnetic and Spin Devices, Volume II)
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12 pages, 1899 KiB  
Article
Mechanism of Topology Change of Flat Magnetic Structures
by Eugene Magadeev, Robert Vakhitov and Ildus Sharafullin
Entropy 2022, 24(8), 1104; https://doi.org/10.3390/e24081104 - 11 Aug 2022
Cited by 13 | Viewed by 1507
Abstract
The paper investigates the processes of the magnetization reversal of perforated ferromagnetic films with strong anisotropy of the easy-plane type. The investigations have shown that, influenced by a current impulse passing through an antidot, an inhomogeneous magnetic structure is formed, which is accompanied [...] Read more.
The paper investigates the processes of the magnetization reversal of perforated ferromagnetic films with strong anisotropy of the easy-plane type. The investigations have shown that, influenced by a current impulse passing through an antidot, an inhomogeneous magnetic structure is formed, which is accompanied by the localization of a quasiparticle with the +1 topological charge on the antidot and by an emission of a quasiparticle with a –1 charge. It is established that this scenario of the film magnetization reversal underlies a reformation of its inhomogeneous structure also if two or four antidots are present in the film, irrespective of the fact of through which antidots and in which directions the currents are passed. The results of the research obtained by using two independent methods (solving the Landau–Lifshitz–Gilbert equations and analyzing the lattice model) demonstrated good agreement between the two. It is shown that a magnetic film comprising two or four antidots can be used as a memory cell for recording data in the ternary system. Full article
(This article belongs to the Section Statistical Physics)
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12 pages, 4081 KiB  
Article
Microstructural Modeling of the Magnetization Process in Ni2MnGa Alloy Polytwin Crystals
by Anatoli A. Rogovoy and Olga S. Stolbova
Magnetochemistry 2022, 8(8), 78; https://doi.org/10.3390/magnetochemistry8080078 - 25 Jul 2022
Cited by 5 | Viewed by 1768
Abstract
In this article, based on the theory of micromagnetism, a microstructural model of the behavior of the Heusler alloy in a magnetic field is constructed. The dynamics of the magnetic process is described by the Landau–Lifshitz–Gilbert equation. Using the Galerkin procedure, variational equations [...] Read more.
In this article, based on the theory of micromagnetism, a microstructural model of the behavior of the Heusler alloy in a magnetic field is constructed. The dynamics of the magnetic process is described by the Landau–Lifshitz–Gilbert equation. Using the Galerkin procedure, variational equations corresponding to the differential relations of the magnetic problem are written out. For numerical simulation, we consider the problem of magnetization of a Ni2MnGa alloy polytwin crystals, each grain of which is a twinned variant of martensite and has pronounced anisotropic properties. First, we consider the process of magnetization of a single grain, when an external magnetic field is applied at different angles to the anisotropy axes of twinned variants, and then, based on the results obtained, we plot magnetization curves for various (isotropic and texture-oriented) polycrystalline samples. This paper does not consider the process of detwinning, which can occur in such a material during the magnetization at a sufficiently high external field strength. Full article
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24 pages, 3511 KiB  
Article
Emergence of Nontrivial Spin Textures in Frustrated Van Der Waals Ferromagnets
by Aniekan Magnus Ukpong
Nanomaterials 2021, 11(7), 1770; https://doi.org/10.3390/nano11071770 - 7 Jul 2021
Cited by 10 | Viewed by 4204
Abstract
In this work, first principles ground state calculations are combined with the dynamic evolution of a classical spin Hamiltonian to study the metamagnetic transitions associated with the field dependence of magnetic properties in frustrated van der Waals ferromagnets. Dynamically stabilized spin textures are [...] Read more.
In this work, first principles ground state calculations are combined with the dynamic evolution of a classical spin Hamiltonian to study the metamagnetic transitions associated with the field dependence of magnetic properties in frustrated van der Waals ferromagnets. Dynamically stabilized spin textures are obtained relative to the direction of spin quantization as stochastic solutions of the Landau–Lifshitz–Gilbert–Slonczewski equation under the flow of the spin current. By explicitly considering the spin signatures that arise from geometrical frustrations at interfaces, we may observe the emergence of a magnetic skyrmion spin texture and characterize the formation under competing internal fields. The analysis of coercivity and magnetic hysteresis reveals a dynamic switch from a soft to hard magnetic configuration when considering the spin Hall effect on the skyrmion. It is found that heavy metals in capped multilayer heterostructure stacks host field-tunable spiral skyrmions that could serve as unique channels for carrier transport. The results are discussed to show the possibility of using dynamically switchable magnetic bits to read and write data without the need for a spin transfer torque. These results offer insight to the spin transport signatures that dynamically arise from metamagnetic transitions in spintronic devices. Full article
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15 pages, 1042 KiB  
Article
Optimized Voltage-Induced Control of Magnetic Domain-Wall Propagation in Hybrid Piezoelectric/Magnetostrictive Devices
by Giancarlo Consolo and Giovanna Valenti
Actuators 2021, 10(6), 134; https://doi.org/10.3390/act10060134 - 17 Jun 2021
Cited by 6 | Viewed by 2421
Abstract
A theory of voltage-induced control of magnetic domain walls propagating along the major axis of a magnetostrictive nanostrip, tightly coupled with a ceramic piezoelectric, is developed in the framework of the Landau–Lifshitz–Gilbert equation. It is assumed that the strains undergone by the piezoelectric [...] Read more.
A theory of voltage-induced control of magnetic domain walls propagating along the major axis of a magnetostrictive nanostrip, tightly coupled with a ceramic piezoelectric, is developed in the framework of the Landau–Lifshitz–Gilbert equation. It is assumed that the strains undergone by the piezoelectric actuator, subject to an electric field generated by a dc bias voltage applied through a couple of lateral electrodes, are fully transferred to the magnetostrictive layer. Taking into account these piezo-induced strains and considering a magnetostrictive linear elastic material belonging to the cubic crystal class, the magnetoelastic field is analytically determined. Therefore, by using the classical traveling-wave formalism, the explicit expressions of the most important features characterizing the two dynamical regimes of domain-wall propagation have been deduced, and their dependence on the electric field strength has been highlighted. Moreover, some strategies to optimize such a voltage-induced control, based on the choice of the ceramic piezoelectric material and the orientation of dielectric poling and electric field with respect to the reference axes, have been proposed. Full article
(This article belongs to the Special Issue New Design and Applications for Magnetoelastic Actuators)
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13 pages, 7742 KiB  
Letter
Micromagnetic Simulations of Submicron Vortex Structures for the Detection of Superparamagnetic Labels
by Lukas Wetterau, Claas Abert, Dieter Suess, Manfred Albrecht and Bernd Witzigmann
Sensors 2020, 20(20), 5819; https://doi.org/10.3390/s20205819 - 15 Oct 2020
Cited by 1 | Viewed by 2819
Abstract
We present a numerical investigation on the detection of superparamagnetic labels using a giant magnetoresistance (GMR) vortex structure. For this purpose, the Landau–Lifshitz–Gilbert equation was solved numerically applying an external z-field for the activation of the superparamagnetic label. Initially, the free layer’s magnetization [...] Read more.
We present a numerical investigation on the detection of superparamagnetic labels using a giant magnetoresistance (GMR) vortex structure. For this purpose, the Landau–Lifshitz–Gilbert equation was solved numerically applying an external z-field for the activation of the superparamagnetic label. Initially, the free layer’s magnetization change due to the stray field of the label is simulated. The electric response of the GMR sensor is calculated by applying a self-consistent spin-diffusion model to the precomputed magnetization configurations. It is shown that the soft-magnetic free layer reacts on the stray field of the label by shifting the magnetic vortex orthogonally to the shift direction of the label. As a consequence, the electric potential of the GMR sensor changes significantly for label shifts parallel or antiparallel to the pinning of the fixed layer. Depending on the label size and its distance to the sensor, the GMR sensor responds, changing the electric potential from 26.6 mV to 28.3 mV. Full article
(This article belongs to the Section Nanosensors)
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12 pages, 2260 KiB  
Article
Magnetic Switching of a Stoner-Wohlfarth Particle Subjected to a Perpendicular Bias Field
by Dong Xue and Weiguang Ma
Electronics 2019, 8(3), 366; https://doi.org/10.3390/electronics8030366 - 26 Mar 2019
Cited by 4 | Viewed by 4372
Abstract
Characterized by uniaxial magnetic anisotropy, the Stoner-Wohlfarth particle experiences a change in magnetization leading to a switch in behavior when tuned by an externally applied field, which relates to the perpendicular bias component (hperp) that remains substantially small in comparison [...] Read more.
Characterized by uniaxial magnetic anisotropy, the Stoner-Wohlfarth particle experiences a change in magnetization leading to a switch in behavior when tuned by an externally applied field, which relates to the perpendicular bias component (hperp) that remains substantially small in comparison with the constant switching field (h0). The dynamics of the magnetic moment that governs the magnetic switching is studied numerically by solving the Landau-Lifshitz-Gilbert (LLG) equation using the Mathematica code without any physical approximations; the results are compared with the switching time obtained from the analytic method that intricately treats the non-trivial bias field as a perturbation. A good agreement regarding the magnetic switching time (ts) between the numerical calculation and the analytic results is found over a wide initial angle range (0.01 < θ0 < 0.3), as h0 and hperp are 1.5 × K and 0.02 × K, where K represents the anisotropy constant. However, the quality of the analytic approximation starts to deteriorate slightly in contrast to the numerical approach when computing ts in terms of the field that satisfies hperp > 0.15 × K and h0 = 1.5 × K. Additionally, existence of a comparably small perpendicular bias field (hperp << h0) causes ts to decrease in a roughly exponential manner when hperp increases. Full article
(This article belongs to the Section Microwave and Wireless Communications)
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10 pages, 1507 KiB  
Article
Ultrafast Modulation of Magnetization Dynamics in Ferromagnetic (Ga, Mn)As Thin Films
by Hang Li, Xinhui Zhang, Xinyu Liu, Margaret Dobrowolska and Jacek K. Furdyna
Appl. Sci. 2018, 8(10), 1880; https://doi.org/10.3390/app8101880 - 11 Oct 2018
Cited by 1 | Viewed by 3083
Abstract
Magnetization precession induced by linearly polarized optical excitation in ferromagnetic (Ga,Mn)As was studied by time-resolved magneto-optical Kerr effect measurements. The superposition of thermal and non-thermal effects arising from the laser pulses complicates the analysis of magnetization precession in terms of magnetic anisotropy fields. [...] Read more.
Magnetization precession induced by linearly polarized optical excitation in ferromagnetic (Ga,Mn)As was studied by time-resolved magneto-optical Kerr effect measurements. The superposition of thermal and non-thermal effects arising from the laser pulses complicates the analysis of magnetization precession in terms of magnetic anisotropy fields. To obtain insight into these processes, we investigated compressively-strained thin (Ga,Mn)As films using ultrafast optical excitation above the band gap as a function of pulse intensity. Data analyses with the gyromagnetic calculation based on Landau-Lifshitz-Gilbert equation combined with two different magneto-optical effects shows the non-equivalent effects of in-plane and out-of-plane magnetic anisotropy fields on both the amplitude and the frequency of magnetization precession, thus providing a handle for separating the effects of non-thermal and thermal processes in this context. Our results show that the effect of photo-generated carriers on magnetic anisotropy constitutes a particularly effective mechanism for controlling both the frequency and amplitude of magnetization precession, thus suggesting the possibility of non-thermal manipulation of spin dynamics through pulsed laser excitations. Full article
(This article belongs to the Special Issue Optics in Spintronic Materials)
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