Magnetostatic waves in a time-dependent medium

Preobrazhenskii, V.V.; Fetisov, Y. K.

doi:10.1007/bf00893542

Cited by 3 publications

(3 citation statements)

References 7 publications

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“…[20][21][22][23][24][25][26][27] These studies predict that a wave that propagates at varying speed (i.e., in a medium with temporally varying dielectric or magnetic constant) is subjected to a variation in amplitude and oscillation period; additionally, reflected waves are generated at time-discontinuities of the medium, similar to what happens at the spatial interface of two media. Experimental studies 20,28 confirmed the predictions regarding amplitude and frequency changes by observing magnetic waves propagating in media subjected to an externally modulated magnetic field. To the best of our knowledge, reflected waves were not observed experimentally.…”

Section: Introductionsupporting

confidence: 55%

Fundamental modeling of wave propagation in temporally relaxing media with applications to cardiac shear wave elastography

Sabbadini

Keijzer

Vos

et al. 2020

The Journal of the Acoustical Society of America

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Shear wave elastography (SWE) might allow non-invasive assessment of cardiac stiffness by relating shear wave propagation speed to material properties. However, after aortic valve closure, when natural shear waves occur in the septal wall, the stiffness of the muscle decreases significantly, and the effects of such temporal variation of medium properties on shear wave propagation have not been investigated yet. The goal of this work is to fundamentally investigate these effects. To this aim, qualitative results were first obtained experimentally using a mechanical setup, and were then combined with quantitative results from finite difference simulations. The results show that the amplitude and period of the waves increase during propagation, proportional to the relaxation of the medium, and that reflected waves can originate from the temporal stiffness variation. These general results, applied to literature data on cardiac stiffness throughout the heart cycle, predict as a major effect a period increase of 20% in waves propagating during a healthy diastolic phase, whereas only a 10% increase would result from the impaired relaxation of an infarcted heart. Therefore, cardiac relaxation can affect the propagation of waves used for SWE measurements and might even provide direct information on the correct relaxation of a heart.

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Section: Introductionsupporting

confidence: 55%

Fundamental modeling of wave propagation in temporally relaxing media with applications to cardiac shear wave elastography

Sabbadini

Keijzer

Vos

et al. 2020

The Journal of the Acoustical Society of America

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“…(vi) A promising avenue for further research lies in combining spatial magnetic gradients, e.g., such as those considered here, with magnetic transients of the kinds considered in Refs. [63][64][65][66].…”

Section: Discussionmentioning

confidence: 99%

Spin-wave wells revisited: From wavelength conversion and Möbius modes to magnon valleytronics

Fripp

Kruglyak

2021

Phys. Rev. B

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We have used micromagnetic simulations to model backward-volume dipole-exchange spin waves in graded profiles of the bias magnetic field. We demonstrate spin-wave wavelength conversion upon the wave's reflection from turning points due to the two characteristic minima ("U points") occurring in their dispersion at finite (nonzero) wave vectors. As a result, backward-volume dipole-exchange spin waves confined in "spin-wave wells" either form Möbius modes, making multiple real-space turns for each reciprocal-space round trip, or split into pairs of degenerate modes in the valleys near the two U points. The latter modes may therefore be assigned a pseudospin. We show that the pseudospin can be switched by scattering the spin wave from decreases of the bias magnetic field, while it is immune to scattering from field increases. Pseudospin creation and read-out can be accomplished using chiral spin-wave transducers, as described in Au et al. [Appl. Phys. Lett. 100, 182404 (2012)] and Au et al. [Appl. Phys. Lett. 100, 172408 (2012)], respectively. Taken together, the possibility of pseudospin creation, manipulation, and read-out suggests a path to development of a spin-wave version of valleytronics ("magnon valleytronics"), in which the pseudospin (rather than amplitude or phase) of spin waves would be used to encode data. Our results are not limited to graded bias magnetic field but can be generalized to other magnonic media with spatially varying characteristics, produced using the toolbox of graded index magnonics.

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“…In all these studies, changes of the spin-wave momenta were reported under conservation of the spin-wave energy. However, there are only few reports on time refraction of spin waves in macroscopic yttrium-iron-garnet waveguides dating back up to 50 years [11][12][13]. Given the lack of spatially resolved methods for mapping spin-wave propagation at that time, these studies could only analyze the change of the spin-wave energy after propagation over several millimeters which limited the speed for changing the magnetic field and the resulting frequency shifts to the megahertz regime.…”

mentioning

confidence: 99%

Time Refraction of Spin Waves

et al. 2021

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We present an experimental study of time refraction of spin waves propagating in microscopic waveguides under the influence of time-varying magnetic fields. Using space-and time-resolved Brillouin light scattering microscopy, we demonstrate that the broken translational symmetry along the time coordinate can be used to in-or decrease the energy of spin waves during their propagation. This allows for a broadband and controllable shift of the spin-wave frequency. Using an integrated design of spin-wave waveguide and microscopic current line for the generation of strong, nanosecondlong, magnetic field pulses, a conversion efficiency up to 39% of the carrier spin-wave frequency is achieved, significantly larger compared to photonic systems. Given the strength of the magnetic field pulses and its strong impact on the spin-wave dispersion relation, the effect of time refraction can be quantified on a length scale comparable to the spin-wave wavelength. Furthermore, we utilize time refraction to excite spin-wave bursts with pulse durations in the nanosecond range and a frequency shift depending on the pulse polarity.

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Magnetostatic waves in a time-dependent medium

Cited by 3 publications

References 7 publications

Fundamental modeling of wave propagation in temporally relaxing media with applications to cardiac shear wave elastography

Fundamental modeling of wave propagation in temporally relaxing media with applications to cardiac shear wave elastography

Spin-wave wells revisited: From wavelength conversion and Möbius modes to magnon valleytronics

Time Refraction of Spin Waves

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