Theory of spin magnetohydrodynamics

Tserkovnyak, Yaroslav; Wong, Clement H.

doi:10.1103/physrevb.79.014402

Cited by 46 publications

(71 citation statements)

References 36 publications

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“…The kinetic coefficients g, ξ, ζ and α can in general also depend on temperature and texture in isotropic materials, for the latter, to the leading order, 2 , etc.. The coefficients p and p ′ describe the so called nondissipative [26,10] coupling of the magnetization dynamics to the charge and energy currents. The corresponding viscous corrections due to electron spin's mistracking of the magnetic texture are described by the coefficients β and β ′ [26,10].…”

Section: Magnetocaloritronic Circuit Elementmentioning

confidence: 99%

“…In order to avoid unnecessary complications, we assume here that even in an out-of-equilibrium situation, when 2 ∂ x T 0 and ∂ x µ 0, H depends only on the instantaneous texture m(x) so that H ≡ ∂ m F. The texture corrections in Eqs. (4) and (5) modify the energy and charge flows and can be relatively large in some cases [10] leading to texture corrections of the Gilbert damping [26] in the LLG Eq. (6).…”

Section: Magnetocaloritronic Circuit Elementmentioning

confidence: 99%

“…The coefficients p and p ′ describe the so called nondissipative [26,10] coupling of the magnetization dynamics to the charge and energy currents. The corresponding viscous corrections due to electron spin's mistracking of the magnetic texture are described by the coefficients β and β ′ [26,10]. The coefficients g, ξ and ζ can be related to the thermal conductivity κ = 1/ζT , the Peltier coefficient Π = ξ/ζ and the conductivity 1/σ = g − Π 2 /κT .…”

Section: Magnetocaloritronic Circuit Elementmentioning

confidence: 99%

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Magnetocaloritronic nanomachines

Kovalev

Tserkovnyak

2010

Solid State Communications

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We introduce and study a magnetocaloritronic circuit element based on a domain wall that can move under applied voltage, magnetic field and temperature gradient. We draw analogies between the Carnot machines and possible devices employing such circuit element. We further point out the parallels between the operational principles of thermoelectric and magnetocaloritronic cooling and power generation and also introduce a magnetocaloritronic figure of merit. Even though the magnetocaloritronic figure of merit turns out to be very small for transition-metal based magnets, we speculate that larger numbers may be expected in ferromagnetic insulators.

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Section: Magnetocaloritronic Circuit Elementmentioning

confidence: 99%

Section: Magnetocaloritronic Circuit Elementmentioning

confidence: 99%

Section: Magnetocaloritronic Circuit Elementmentioning

confidence: 99%

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Magnetocaloritronic nanomachines

Kovalev

Tserkovnyak

2010

Solid State Communications

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“…The dissipative coupling between the magnetization and the normal component is shown to give rise to magnetization relaxation that is fourth order in spatial gradients of the magnetization direction. In metallic ferromagnets, magnetization dynamics leads to forces on quasiparticles of geometric origin called spin motive forces, that have gained considerable attention recently [8][9][10][11][12]. Furthermore, spin textures with nonzero chirality, such as the skyrmion lattice observed recently [13,14] induce the so-called topological Hall effect [5,6].…”

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Magnetization Relaxation and Geometric Forces in a Bose Ferromagnet

2013

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We construct the hydrodynamic theory for spin-1/2 Bose gases at arbitrary temperatures. This theory describes the coupling between the magnetization, and the normal and superfluid components of the gas. In particular, our theory contains the geometric forces on the particles that arise from their spin's adiabatic following of the magnetization texture. The phenomenological parameters of the hydrodynamic theory are calculated in the Bogoliubov approximation and using the Boltzmann equation in the relaxation-time approximation. We consider the topological Hall effect due to the presence of a skyrmion, and show that this effect manifests itself in the collective modes of the system. The dissipative coupling between the magnetization and the normal component is shown to give rise to magnetization relaxation that is fourth order in spatial gradients of the magnetization direction. In metallic ferromagnets, magnetization dynamics leads to forces on quasiparticles of geometric origin called spin motive forces, that have gained considerable attention recently [8][9][10][11][12]. Furthermore, spin textures with nonzero chirality, such as the skyrmion lattice observed recently [13,14] induce the so-called topological Hall effect [5,6]. In addition, the coupling between magnetization and quasiparticles has also been shown to give rise to novel forms of magnetization relaxation in this case. A prominent example is inhomogeneous Gilbert damping [15][16][17]. This effect is important in clean solid-state systems. We therefore expect these effects to be particularly important for gases of ultracold atoms, that, in contrast to conventional condensed-matter systems, are free of impurities.The field of ultracold atoms is characterised by exquisite experimental control [18][19][20]. Relevant for our focus is the great amount of recent activity on spinor Bose gases. Firstly, it has been discovered that these gases can be either ferromagnetic or antiferromagnetic depending on the details of the scattering lengths [21,22]. Furthermore, numerous studies at zero temperature, based on the Gross-Pitaevskii equation, have elucidated the longwavelength properties of spinor gases [23,24]. Other areas of current interest in the field include topological excitations, magnetic dipole-dipole interactions and nonequilibrium quantum dynamics [25]. The recent progress in the understanding of ferromagnetic spinor gases and their manipulation by light has also enabled detailed studies of magnetization dynamics [26,27].

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“…A complete picture of our coupled magnetohydrodynamic system requires us to consider also the spin-transfer torque that is reciprocal to the DW-driven electromotive forces [13]. Such torque acting on the magnetization is given, due to the MI/TI exchange (see ST for details)…”

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Thin-Film Magnetization Dynamics on the Surface of a Topological Insulator

2012

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We theoretically study the magnetization dynamics of a thin ferromagnetic film exchange-coupled with a surface of a strong three-dimensional topological insulator. We focus on the role of electronic zero modes imprinted by domain walls (DW's) or other topological textures in the magnetic film. Thermodynamically reciprocal hydrodynamic equations of motion are derived for the DW responding to electronic spin torques, on the one hand, and fictitious electromotive forces in the electronic chiral mode fomented by the DW, on the other. An experimental realization illustrating this physics is proposed based on a ferromagnetic strip, which cuts the topological insulator surface into two gapless regions. In the presence of a ferromagnetic DW, a chiral mode transverse to the magnetic strip acts as a dissipative interconnect, which is itself a dynamic object that controls (and, inversely, responds to) the magnetization dynamics.PACS numbers: 72.15.Gd, Following theoretical predictions [1] and experimental realizations [2] of three-dimensional topological insulators (TI's), vigorous ongoing activities in this burgeoning field are aimed at introducing spontaneous symmetry breaking mechanisms into the system. This could be accomplished by bulk or surface doping to induce magnetism or superconductivity in the parent (essentially free-electron) TI, or by a heterostructure design wherein symmetry breaking is instilled at the TI surface by a quantum proximity effect. We are following the latter route, considering an insulating ferromagnetic layer (MI) capping the bulk TI, such that the TI surface states are exchange coupled to the collective magnetic moment of the MI. Previous theoretical investigations of a similar TI/MI heterostructure were concerned with currentinduced spin torques experienced by a monodomain MI [4], Gilbert damping by a doped TI [4], electric charging of magnetic textures [4], and the rectification of charge pumping by a monodomain precession [4], all in case of a well-defined spatially uniform sign of the time-reversal symmetry breaking gap in the TI. The essential physical ingredient underlying the key ideas in these papers is the axion electrodynamics [3] associated with the TI [8], with a quantized magnetoelectric coupling that is odd under time reversal. In this Letter, we are interested in salient features associated with dynamic magnetic textures that imprint a spatially inhomogeneous gap onto the TI surface states, both in regard to its magnitude and sign. The latter, in particular, engenders electronic chiral modes at the magnetic domain boundaries [1], whose hydrodynamics become intricately coupled with magnetic precession.According to the spin-charge helicity of the TI electronic states, the spin-transfer torques acting on the MI are locked with the self-consistent electronic charge currents in the TI. These currents, in turn, can respond to a combination of electromagnetic fields and fictitious forces induced by MI dynamics, having several distinct contributions: (i) two-dimensional (2D) surface c...

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Theory of spin magnetohydrodynamics

Cited by 46 publications

References 36 publications

Magnetocaloritronic nanomachines

Magnetocaloritronic nanomachines

Magnetization Relaxation and Geometric Forces in a Bose Ferromagnet

Thin-Film Magnetization Dynamics on the Surface of a Topological Insulator

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