Graded-index magnonics

Davies, C. S.; Kruglyak, V. V.

doi:10.1063/1.4932349

Cited by 48 publications

(41 citation statements)

References 86 publications

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“…Furthermore, recent experimental studies showed an efficient spin-wave electrical tuning in thin magnetic films, such as YIG (Y 3 Fe 5 O 12 ) [4]. At present, interest to such phenomena is very active due to their potential applications in magnon spintronics and magnonics [7][8][9], where an electrically controlled phase shifter for spin waves could become an essential component of spin-wave devices. Nonreciprocity and unidirectionality of spin-wave propagation would be also valuable for this purpose [10].…”

Section: Introductionmentioning

confidence: 99%

Electric-field control of spin-wave power flow and caustics in thin magnetic films

2018

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An external electric field can modify the strength of the spin-orbit interaction between spins of ions in magnetic crystals. This influence leads to a spin-wave frequency shift that is linear in both the applied electric field and the wave vector of the spin wave. Here we study theoretically the external electric field as a means of control of the spin-wave power flow in thin ferromagnets. The spin-wave group velocity and focusing patterns are obtained from the slowness (isofrequency) curves by evaluating their curvature at each point of the reciprocal space. We show that the combination of the magnetodipole interaction and the electric field can result in nonreciprocal unidirectional caustic beams of dipole-exchange spin waves. We demonstrate that the degree of asymmetry of the spin-wave power flow can be tuned with the external electric field. Our findings open a novel avenue for spin-wave manipulation and development of electrically tunable magnonic devices.

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Section: Introductionmentioning

confidence: 99%

Electric-field control of spin-wave power flow and caustics in thin magnetic films

2018

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“…[10,31] where the domain wall oscillations at frequency ω were observed to emit spin waves at twice the frequency, i.e., 2ω. Our theory suggests that the spin wave emission from domain walls, at a frequency equal to that of the driving magnetic field [12,13] or spin-polarized current [14] should rather be interpreted as a linear excitation due to the magnetic inhomogeneity [32] ("graded magnonic index" [20]) created by the domain wall, when excited by a uniform magnetic field.…”

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“…This potential is mostly known for its peculiar property of 100% transmission of incident waves at any frequency, for certain parameters of the potential [19]. While forming such a potential in other systems is difficult, serendipitously the reflectionless Pöschl-Teller potential exactly describes the graded magnonic index profile [20] due to a Bloch domain wall, allowing the peculiar behavior to be both investigated and exploited in magnetic systems [21]. Furthermore, when the domain wall is driven by a uniform microwave magnetic field, the Pöschl-Teller profile happens to be present not only as the potential, but also as a driving term in the obtained Schrödinger-like equation.…”

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Theory of linear spin wave emission from a Bloch domain wall

et al. 2017

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We report an analytical theory of linear emission of exchange spin waves from a Bloch domain wall, excited by a uniform microwave magnetic field. The problem is reduced to a one-dimensional Schrödinger-like equation with a Pöschl-Teller potential and a driving term of the same profile. The emission of plane spin waves is observed at excitation frequencies above a threshold value, as a result of a linear process. The height-to-width aspect ratio of the Pöschl-Teller profile for a domain wall is found to correspond to a local maximum of the emission efficiency. Furthermore, for a tailored Pöschl-Teller potential with a variable aspect ratio, particular values of the latter can lead to enhanced or even completely suppressed emission.Wave generation is both an essential topic in wave physics and a prerequisite of any technology exploiting waves. Conventionally, waves are excited using an antenna, with their wavelength being limited by the antenna's size. Alternatively, we could use an inhomogeneity (either deliberately introduced, or naturally-occuring) in the medium and then apply a uniform, oscillatory external field to generate a wave. Small wavelength excitations require equally small antennas or inhomogeneities to generate them.In magnonics [1][2][3], the study of spin waves, we are fortunate that inhomogeneities with nanoscale dimensions naturally occur in magnetic materials: domain walls. These inhomogeneities are the transition regions between domains of uniformly aligned magnetization, and can have dimensions down to a few nanometers, depending on the material. Domain walls have been studied in great detail, due to a number of interesting properties: their magnetic field and current-driven motion [4,5], their ability to channel spin waves [6][7][8], and the unusual reflectionless behavior for spin waves passing through them [9]. Recently, there have also been numerical [10,11] and experimental [12,13] reports of pinned domain walls generating spin waves, with wavelengths down to tens of nanometers [14]. The origin of the observed spin wave emission has typically been attributed to the domain wall oscillations, generated by the applied microwave magnetic field [10][11][12][13] or spin-polarized current [14,15].In this letter, we report an analytical theory that demonstrates emission of exchange spin waves from a Bloch domain wall driven by a uniform microwave magnetic field, as a result of a linear process. The problem is reduced to that of the Pöschl-Teller potential in a Schrödinger-like equation -an exactly solvable model, of particular interest in quantum mechanics [16] and optics [17,18]. This potential is mostly known for its peculiar property of 100% transmission of incident waves at any frequency, for certain parameters of the potential [19]. While forming such a potential in other systems is difficult, serendipitously the reflectionless Pöschl-Teller potential exactly describes the graded magnonic index profile [20] due to a Bloch domain wall, allowing the peculiar behavior to be both investigated a...

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“…Other methods of modifying the dispersion include the magnonic crystals employing magnetic superlattices [1,14], and the gradient-index magnonics employing non-uniform effective magnetic field configurations [15,16].…”

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Magnetic Snell's law and spin-wave fiber with Dzyaloshinskii-Moriya interaction

Lan

et al. 2016

Phys. Rev. B

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Graded-index magnonics

Cited by 48 publications

References 86 publications

Electric-field control of spin-wave power flow and caustics in thin magnetic films

Electric-field control of spin-wave power flow and caustics in thin magnetic films

Theory of linear spin wave emission from a Bloch domain wall

Magnetic Snell's law and spin-wave fiber with Dzyaloshinskii-Moriya interaction

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