Unidirectional Chiral Magnonics in Cylindrical Synthetic Antiferromagnets

Gallardo, R. A.; Alvarado-Seguel, P.; Landeros, P.

doi:10.1103/physrevapplied.18.054044

Cited by 7 publications

(4 citation statements)

References 86 publications

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“…For the lowest magnon band, self-focusing spin-wave beams arise at frequencies in the range of 1 to 14.5 GHz with wavenumbers up to 70 rad/μm, and their predicted emission angles and group velocities are strongly frequency dependent. In perspective, while the nonreciprocity factor found in this work is much higher than the ones observed earlier, it may still be increased by tailoring the design of the layer stack (for example, by reducing the interlayer thickness) and by exploiting curvilinear effects. , Such spin-wave nonreciprocities could be exploited for the realization of spin-wave isolator or circulator devices. Note, however, that the purpose of the present study was to demonstrate nonreciprocal coherent spin-wave propagation on a basic scientific level and that for real-world devices likely other ways of implementation are required in terms of functional areal density and spin-wave excitation efficiency.…”

Section: Discussionmentioning

confidence: 99%

Coherent Magnons with Giant Nonreciprocity at Nanoscale Wavelengths

Gallardo,

Weigand,

Schultheiss

et al. 2024

ACS Nano

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Nonreciprocal wave propagation arises in systems with broken time-reversal symmetry and is key to the functionality of devices, such as isolators or circulators, in microwave, photonic, and acoustic applications. In magnetic systems, collective wave excitations known as magnon quasiparticles have so far yielded moderate nonreciprocities, mainly observed by means of incoherent thermal magnon spectra, while their occurrence as coherent spin waves (magnon ensembles with identical phase) is yet to be demonstrated. Here, we report the direct observation of strongly nonreciprocal propagating coherent spin waves in a patterned element of a ferromagnetic bilayer stack with antiparallel magnetic orientations. We use time-resolved scanning transmission X-ray microscopy (TR-STXM) to directly image the layer-collective dynamics of spin waves with wavelengths ranging from 5 μm down to 100 nm emergent at frequencies between 500 MHz and 5 GHz. The experimentally observed nonreciprocity factor of these counter-propagating waves is greater than 10 with respect to both group velocities and specific wavelengths. Our experimental findings are supported by the results from an analytic theory, and their peculiarities are further discussed in terms of caustic spin-wave focusing.

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Section: Discussionmentioning

confidence: 99%

Coherent Magnons with Giant Nonreciprocity at Nanoscale Wavelengths

Gallardo,

Weigand,

Schultheiss

et al. 2024

ACS Nano

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“…Moreover, higher-order propagating modes 11 , 12 , perpendicular standing waves 13 and modes supported by complex spin textures 14 , 15 display a wealth of distinctive three-dimensional features. Beyond thin films, the morphology of three-dimensional magnetic nanostructures 16 – 18 and curvilinear systems 19 , 20 can induce novel effects in the spin-wave properties. Such aspects are crucial for the young field of three-dimensional magnonics 21 which, following the trend of electronics and photonics, aims to harness the third dimension to realize novel functionalities in devices.…”

Section: Introductionmentioning

confidence: 99%

Three-dimensional spin-wave dynamics, localization and interference in a synthetic antiferromagnet

Girardi,

Finizio,

Donnelly

et al. 2024

Nat Commun

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Spin waves are collective perturbations in the orientation of the magnetic moments in magnetically ordered materials. Their rich phenomenology is intrinsically three-dimensional; however, the three-dimensional imaging of spin waves has so far not been possible. Here, we image the three-dimensional dynamics of spin waves excited in a synthetic antiferromagnet, with nanoscale spatial resolution and sub-ns temporal resolution, using time-resolved magnetic laminography. In this way, we map the distribution of the spin-wave modes throughout the volume of the structure, revealing unexpected depth-dependent profiles originating from the interlayer dipolar interaction. We experimentally demonstrate the existence of complex three-dimensional interference patterns and analyze them via micromagnetic modelling. We find that these patterns are generated by the superposition of spin waves with non-uniform amplitude profiles, and that their features can be controlled by tuning the composition and structure of the magnetic system. Our results open unforeseen possibilities for the study and manipulation of complex spin-wave modes within nanostructures and magnonic devices.

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“…[5][6][7][8][9][10][11][12]. Some reviews covering the effects of DMI on the magnetization statics and dynamics in ferromagnetic nanostructures are [4,[13][14][15][16]. In general, it is known that DMI can also produce chiral and topological features in nanostructures [13,17,18], opening up new perspectives for device applications.…”

Section: Introductionmentioning

confidence: 99%