Excitation Spectrum of Magnetic Domain Walls

Thiele, A. A.

doi:10.1103/physrevb.7.391

Cited by 79 publications

(42 citation statements)

References 8 publications

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“…The presence of inhomogeneities, whether intrinsic (lattice defects, boundaries) or configurational (domain walls, Skyrmions), changes this picture. Such defects do not only affect the dynamics of the spin waves; they also often give rise to special low-energy normal modes that are localized near the defect [12][13][14]. The modes localized on configurational defects are particularly interesting.…”

Section: Introductionmentioning

confidence: 99%

Zero modes in magnetic systems: General theory and an efficient computational scheme

2014

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The presence of topological defects in magnetic media often leads to normal modes with zero frequency (zero modes). Such modes are crucial for long-time behavior, describing, for example, the motion of a domain wall as a whole. Conventional numerical methods to calculate the spin-wave spectrum in magnetic media are either inefficient or they fail for systems with zero modes. We present a new efficient computational scheme that reduces the magnetic normal-mode problem to a generalized Hermitian eigenvalue problem also in the presence of zero modes. We apply our scheme to several examples, including two-dimensional domain walls and Skyrmions, and show how the effective masses that determine the dynamics can be calculated directly. These systems highlight the fundamental distinction between the two types of zero modes that can occur in spin systems, which we call special and inertial zero modes. Whereas the inertial modes are generic Goldstone modes related to a broken continuous symmetry, the special modes arise naturally when two broken continuous symmetries coexist. Our method is suitable for both conservative and dissipative systems. For the latter case, we present a perturbative scheme to take into account damping, which can also be used to calculate dynamical susceptibilities.

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Section: Introductionmentioning

confidence: 99%

Zero modes in magnetic systems: General theory and an efficient computational scheme

2014

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“…Hence, in contrast to conventional STT whose operation requires the use of ferromagnetic metals, magnonic STT can work in ferromagnetic insulators, ame-(a) E-mail: dwwang@nudt.edu.cn (b) E-mail: guogh@mail.csu.edu.cn liorating significantly the Joule heating problem in metals. However, the MT due to the reflection of magnons by a DW is rarely discussed, simply because magnons travel in an infinitely-extended one-dimensional (1D) wall without any reflection [10][11][12]. The only effect of the presence of a DW is a wave-number dependent phase shift.…”

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confidence: 99%

Magnonic momentum transfer force on domain walls confined in space

Wang¹,

Wang²,

Guo³

2013

EPL

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PACS 75.30.Ds -Spin waves PACS 75.60.Ch -Domain walls and domain structure Abstract -Momentum transfer from incoming magnons to a Bloch domain wall is calculated using one dimensional continuum micromagnetic analysis. Due to the confinement of the wall in space, the dispersion relation of magnons is different from that of a single domain. This mismatch of dispersion relations can result in reflection of magnons upon incidence on the domain wall, whose direct consequence is a transfer of momentum between magnons and the domain wall. The corresponding counteraction force exerted on the wall can be used for the control of domain wall motion through magnonic linear momentum transfer, in analogy with the spin transfer torque induced by magnonic angular momentum transfer.Ever since its first proposal, manipulation of domain wall motion (DWM) using means other than the conventional magnetic field becomes one focus of the current research in nanomagnetism. The stimulus behind such intense investigation to find new ways for control of DWM is obvious, given the potential application of magnetic domain walls (DWs) as logic elements [1] and information storage bits [2]. Hydromagnetic drag [3], spin transfer torque (STT) [4,5] and momentum transfer (MT) force [6] due to the flow of electrons in metallic materials were proposed, and STT driven DWM was already demonstrated experimentally [7,8]. In contrast, using another important elementary excitation, magnons, to affect the motion of DW comes into horizon only recently. Magnon mediated electric current drag in a normal metal/ferromagnetic insulator/normal metal structure was studied by considering the interplay between electrical current and magnon current [9]. Magnonic STT was demonstrated, employing micromagnetic simulation and analytical calculation [10]. The main difference, or advantage, of magnonic STT compared to the conventional electronic STT lies on the fact that it is mediated by the flow of magnons, rather than electrons. Hence, in contrast to conventional STT whose operation requires the use of ferromagnetic metals, magnonic STT can work in ferromagnetic insulators, ame-(a) E-mail: dwwang@nudt.edu.cn (b) E-mail: guogh@mail.csu.edu.cn liorating significantly the Joule heating problem in metals. However, the MT due to the reflection of magnons by a DW is rarely discussed, simply because magnons travel in an infinitely-extended one-dimensional (1D) wall without any reflection [10][11][12]. The only effect of the presence of a DW is a wave-number dependent phase shift. For a 1D DW confined in space, the situation is different. Due to the fact that the magnon excitation spectrum of the DW is different from that of a single domain, magnons incident on the DW get reflected, with a frequency-sensitive coefficient of reflection. As magnons are reflected back, a counteraction force is exerted on the DW and can be used to initiate DWM [13].In the presence of pure magnonic STT, DWs will move opposite to the propagation direction of the incident spin wave (SW) [10]. However,...

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“…Manipulation of a magnetic domain wall (DW) in nanostructures draws much attention for its potential applications [1][2][3] and academic interest as a nonlinear system [4,5]. DW dynamics is governed by the Landau-Lifshitz-Gilbert (LLG) equation.…”

Section: Introductionmentioning

confidence: 99%

Spin wave emission in field-driven domain wall motion

Wang

2014

Phys. Rev. B

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A domain wall (DW) in a nanowire can propagate under a longitudinal magnetic field by emitting spin waves (SWs). We numerically investigated the properties of SWs emitted by the DW motion, such as frequency and wave number, and their relation with the DW motion. For a wire with a low transverse anisotropy and in a field above a critical value, a DW emits SWs to both sides (bow and stern), while it oscillates and propagates at a low average speed. For a wire with a high transverse anisotropy and in a weak field, the DW emits mostly stern waves, while the DW distorts itself and the DW center propagates forward like a drill at a relative high speed.

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Excitation Spectrum of Magnetic Domain Walls

Cited by 79 publications

References 8 publications

Zero modes in magnetic systems: General theory and an efficient computational scheme

Zero modes in magnetic systems: General theory and an efficient computational scheme

Magnonic momentum transfer force on domain walls confined in space

Spin wave emission in field-driven domain wall motion

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