Spin wave dynamics and magnonics

Magnonics is a growing field of research focused on magnetic excitations, i.e. spin-waves (or magnons, their quanta) [KRUG2010]. The objective is to exploit spin-waves (SWs) to carry and process information. The possibility of integrating ferromagnetic materials directly in micro-electronic circuits is attractive because firstly, the typical time (ps to ns) and length (nm to μm) scales of SWs nicely match those of modern micro-electronics, and secondly, it allows to make non-volatile reconfigurable microwave devices. Moreover, magnonic devices are intrinsically weakly dissipative due to the absence of moving charges. The unique features of SW propagation, which can be tuned by a bias magnetic field and controlled by nanostructuration in magnonic crystals [KRAW2014], combined with the undulatory nature and the intrinsic nonlinear properties of magnons, make it possible the development, among others, of non-Boolean computing schemes, spin-wave logic, and novel types of microwave signal processing. The field of magnonics has also recently benefit from synergies with the field of spintronics [CHUM2015], with the promise to develop a novel hardware paradigm for sustainable information technology based on the transport of pure spin currents. Exploiting spinorbitronic effects (spin torque, spin-charge conversion, etc), it is indeed possible to excite, detect and control SWs [DEMI2017].

Magnonics has now become a booming field with many interesting research lines [CHUM2017]. Based on the know-how to grow low-loss magnetic materials such as YIG in the form of ultra-thin films [DALL2013] and to nanopattern them without deterioration of their dynamical properties [HAHN2014], the teams involved in SPiCY have mainly contributed to the topic of magnon spintronics, with the demonstration that spin-orbit torque (SOT) could be used to control the relaxation of stationary [COLL2016] and propagating [EVEL2016] SWs (see Fig. 4). Progress in this direction make the concept of active magnon-based media plausible. Still some crucial issues arising from nonlinear couplings between SW modes, which limit the SW amplification, and the efficient transduction of SWs to electrical signals, need to be tackled. In parallel, there have been some interesting proposals to use magnetic textures [GARC2015], and topological properties induced by either dipole-dipole [SHIN2013] or Dzyaloshinskii-Moriya interactions (DMI) [ZHAN2013], and even patterning [LI2018], to control the SW spectrum and propagation. Some recent experimental works have also demonstrated that chiral magnetism could be induced in insulating magnetic garnets [AVCI2019], and that nonlinear.

Figure 4: Stimulated amplification of SWs by spin-orbit torque. (a) µ-BLS imaging of SW propagating at 5 GHz in a straight YIG|Pt slab magnetized in-plane. (b) SW decay for different currents in the Pt. (c) Current dependences of the decay constant and of the propagation length.


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J. Phys. D: Appl. Phys. 43, 264001 (2010)

[KRAW2014] M. Krawczyk and D. Grundler
Review and prospects of magnonic crystals and devices with reprogrammable band structure
J. Phys.: Condens. Matter 26, 123202 (2014)

[CHUM2015] A.V. Chumak et al
Magnon spintronics
Nature Phys. 11, 453–461 (2015)

[DEMI2017] V.E. Demidov et al.
Magnetization oscillations and waves driven by pure spin currents
Phys. Rep. 673, 1 (2017)

[CHUM2017] A.V. Chumak and H. Schultheiss
Magnonics: spin waves connecting charges, spins and photons
J. Phys. D: Appl. Phys. 50, 300201 (2017)

[DALL2013] O. d’Allivy Kelly et al.
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Appl. Phys. Lett. 103, 082408 (2013)

[HAHN2014] C. Hahn et al.
Measurement of the intrinsic damping constant in individual nanodisks of Y3Fe5O12 and Y3Fe5O12/Pt
Appl. Phys. Lett. 104, 152410 (2014)

[COLL2016] M. Collet et al.
Generation of coherent spin-wave modes in YIG microdiscs by spin-orbit torque
Nature Comm. 7, 10377 (2016)

[EVEL2016] M. Evelt et al.
High-efficiency control of spin-wave propagation in ultra-thin YIG by the spin-orbit torque
Appl. Phys. Lett. 108, 172406 (2016)

[GARC2015] F. Garcia-Sanchez et al.
Narrow Magnonic Waveguides Based on Domain Walls
Phys. Rev. Lett. 114, 247206 (2015)

[SHIN2013] R. Shindou et al.
Topological chiral magnonic edge mode in a magnonic crystal
Phys. Rev. B 87, 174427 (2013)

[ZHAN2013] L. Zhang et al
Topological magnon insulator in insulating ferromagnet
Phys. Rev. B 87, 144101 (2013)

[LI2018] Y.-M. Li et al.
Topological Magnon Modes in Patterned Ferrimagnetic Insulator Thin Films
Nano Lett. 18, 3032 (2018)

[AVCI2019] O. Avci et al.
Interface-driven chiral magnetism and current-driven domain walls in insulating magnetic garnets
Nature Nanotech. 14, 561 (2019