Breather Induced Modification of the Speed of Sound

Hu, Bambi; Tekić, Jasmina

doi:10.1103/physrevlett.87.035502

Cited by 5 publications

(2 citation statements)

References 22 publications

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“…Consequently, the kinetic energy is supplied to the kink crystal and the ultrasound attenuation may occur. 51 Then, the attenuation rate should change upon changing the applied magnetic field strength.…”

Section: Ultrasound Attenuation Under the Magnetic Fieldmentioning

confidence: 99%

Theory of spin current in chiral helimagnet

Bostrem,

Kishine,

Ovchinnikov

2008

Preprint

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We give detailed description of the transport spin current in the chiral helimagnet. Under the static magnetic field applied perpendicular to the helical axis, the magnetic kink crystal (chiral soliton lattice) is formed. Once the kink crystal begins to move under the Galilean boost, the spin-density accumulation occurs inside each kink and there emerges periodic arrays of the induced magnetic dipoles carrying the transport spin current. The coherent motion of the kink crystal dynamically generates the spontaneous demagnetization field. This mechanism is analogous to the Döring-Becker-Kittel mechanism of the domain wall motion in ferromagnets. To describe the kink crystal motion, we took account of not only the tangential ϕ-fluctuations but the longitudinal θfluctuations around the helimagnetic configuration. Based on the collective coordinate method and the Dirac's canonical formulation for the singular Lagrangian system, we derived the closed formulae for the mass, spin current and induced magnetic dipole moment accompanied with the kink crystal motion. To materialize the theoretical model presented here, symmetry-adapted material synthesis would be required, where the interplay of crystallographic and magnetic chirality plays a key role there.

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Section: Ultrasound Attenuation Under the Magnetic Fieldmentioning

confidence: 99%

Theory of spin current in chiral helimagnet

Bostrem,

Kishine,

Ovchinnikov

2008

Preprint

View full text Add to dashboard Cite

show abstract

“…Consequently, the ultrasound attenuation may occur. 20 TOF technique: the most direct way of detecting the traveling magnon density may be winding a sample by a pick-up coil and performing the time-offlight (TOF) experiment. Then, the coil should detect a periodic signal induced by the magnetic current.…”

mentioning

confidence: 99%

Transport spin current driven by the moving kink crystal in a chiral helimagnet

Bostrem¹,

Kishine

Овчинников³

2008

Phys. Rev. B

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We show that the bulk transport magnetic current is generated by the moving magnetic kink crystal (chiral soliton lattice) formed in the chiral helimagnet under the static magnetic field applied perpendicular to the helical axis. The current is caused by the non-equilibrium transport momentum with the kink mass being determined by the spin fluctuations around the kink crystal state. An emergence of the transport magnetic currents is then a consequence of the dynamical off-diagonal long range order along the helical axis. We derive an explicit formula for the inertial mass of the kink crystal and the current in the weak field limit. PACS numbers: Valid PACS appear hereHow to create, transport, and manipulate spin currents is a central problem in the multidisciplinary field of spintronics.1 The key theoretical concepts there include the current-driven spin-transfer torque 2 and resultant force acting on a domain wall (DW) 3 in metallic ferromagnetic/nonmagnetic multilayers, the dissipationless spin currents in paramagnetic spin-orbit coupled systems, 4 and magnon transport in textured magnetic structures.5 A fundamental query behind the issue is how to describe transport magnetic currents.6 Conventionally, the charge current is defined by the product of the carrier density and the drift velocity related via the continuity equation. In the case of spin current, the deviation of the spin projection from its equilibrium value plays a role of a charge. Then, an emergence of the transport magnetic currents may be expected in non-equilibrium state as a manifestation of the dynamical off-diagonal long range order (ODLRO).7 Historically, Döring first pointed out that the longituidal component of the slanted magnetic moment inside the Bloch DW emerges as a consequence of translational motion of the DW.8 An additional magnetic energy associated with the resultant demagnetization field is interpreted as the kinetic energy of the wall.Recent progress of material synthesis sheds new light on this problem. In a series of magnets belonging to chiral space group without any rotoinversion symmetry elements, the crystallographic chirality gives rise to the asymmetric Dzyaloshinskii interaction that stabilizes either left-handed or right-handed chiral magnetic structures.9 In these chiral helimagnets, magnetic field applied perpendicular to the helical axis stabilizes a periodic array of DWs with definite spin chirality forming kink crystal or chiral soliton lattice.10 In this paper, we demonstrate that the magnetic transport analogous to Döring effect 8 occurs in the moving kink crystal of chiral helimagnets and serves an example of the dynamical ODLRO in non-equilibrium state. An essential point is that the kink crystal state has a degeneracy originating from the translational symmetry. Consequently, the transport momentum has a form MẊ, where M and X represent the kink mass and the collective coordinate of the kink in the laboratory frame. The kink crystal behaves as a heavy object with the inertial mass M .We start with a spin...

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