Linear and nonlinear magnonic crystals
Final Report Abstract
Magnonic crystals (MCs) are artificial magnetic media with periodic variation of their magnetic properties in space. Their name relates to the magnon – the quasiparticle associated with a spin-wave – a propagating disturbance in the local magnetic order. Bragg scattering affects a spin-wave spectrum in such periodic structure and leads to the formation of band gaps – frequencies at which spin-wave propagation is prohibited. The pronounced changes of the spin-wave dispersion near the bandgap edges open access to the deceleration of spin waves and the appearance of confined spin-wave modes. Magnonic crystals are rapidly gaining recognition as structures, which have much to contribute not only to the study and technological application of spin waves, but also to our general understanding of complex wave dynamics. Dynamic magnonic crystals, first created and investigated in the project, feature an artificial lattice that can be switched “off” and “on” on a timescale which is short in comparison to the time taken for a spinwave packet to propagate through it. In the wider context of artificial crystals, this fast-switching functionality is unique. We have developed a few designs of electric current-controlled dynamic crystals and for the first time realized complex spectral transformations such as time reversal, which until now have only been demonstrated through the exploitation of non-linear wave media. In the particular context of spin-wave dynamics, our experimental results directly demonstrate that dynamically controlled magnonic crystal systems open doors to sophisticated spin-information processing functionality which might be exploited in future magnonic and spintronic devices. Two materials dominate our experimental studies: single-crystal yttrium iron garnet (YIG, Y3Fe5O12) and the polycrystalline metallic alloy Permalloy (Py, Ni81Fe19). Yttrium iron garnet is an electrically insulating ferrimagnet, in monocrystalline form its spin-wave damping is uniquely low, allowing propagating spin waves to be observed over centimeter distances. Relatively large-scale magnonic crystals fabricated from monocrystalline YIG films (typical thicknesses in the micron range and lateral dimensions of order several millimeters) provide us the perfect model system for the detailed study of the underlying physics of linear and nonlinear spin-wave propagation in magnonic crystal systems. We investigated experimentally and theoretically the propagation of volume and surface magnetostatic spin waves through the YIG-based magnonic crystals produced in the form of chemically etched surface grooves and defined the optimal crystal parameters for both types of waves. The phenomenon of coherent wave trapping and restoration was demonstrated in a YIG-based magnonic crystal. Unlike the conventional scheme used in photonics, the trapping occurs not due to the deceleration of the incident wave when it enters the periodic structure but due to excitation of the quasi-normal modes of the artificial crystal. This excitation occurs at the group velocity minima of the decelerated wave in narrow frequency regions near the edges of the band gaps of the crystal. The restoration of the traveling wave was implemented by means of phase-sensitive parametric amplification of the stored mode. Moreover, using a YIG-based magnonic crystal to enhance nonlinear magnon–magnon interactions, we have succeeded in the realization of magnon-by-magnon control, and the development of a magnon transistor. We have shown that the density of magnons flowing from the transistor’s source to its drain can be decreased three orders of magnitude by the injection of magnons into the transistor’s gate connected with the magnonic crystal. Despite the fact that the spin-wave free path in thin-film Permalloy is of the order of tens of microns, the ease which Py can be deposited and patterned makes it an attractive material for experimental studies of complex geometries and micro- and nanoscale devices. It was used by us to fabricate a number of micro-sized magnonic crystals, including with-modulated, ion-implanted, and twodimensionally patterned systems.
Publications
- Scattering of backward spin waves in one-dimensional magnonic crystal, Appl. Phys. Lett. 93, 022508 (2008)
A.V. Chumak, A.A. Serga, B. Hillebrands, M.P. Kostylev
- A current-controlled, dynamic magnonic crystal, J. Phys. D: Appl. Phys.42, 205005 (2009)
A.V. Chumak, T. Neumann, A.A. Serga, B. Hillebrands, M.P. Kostylev
- Design and optimization of one-dimensional ferrite-film based magnonic crystals, J. Appl. Phys. 105, 083906 (2009)
A.V. Chumak, A.A. Serga, S. Wolff, B. Hillebrands, M.P. Kostylev
- Generation of spin-wave pulse trains by current-controlled magnetic mirrors, Appl. Phys. Lett. 94, 112501 (2009)
A.A. Serga, T. Neumann, A.V. Chumak, B. Hillebrands
- Scattering of surface and volume spin waves in a magnonic crystal, Appl. Phys. Lett. 94, 172511 (2009)
A.V. Chumak, A.A. Serga, S. Wolff, B. Hillebrands, M.P. Kostylev
- Spin-wave propagation in a microstructured magnonic crystal, Appl. Phys. Lett. 95, 262508 (2009)
A.V. Chumak, P. Pirro, A.A. Serga, M.P. Kostylev, R.L. Stamps, H. Schultheiss, K. Vogt, S.J. Hermsdoerfer, B. Laegel, P.A. Beck, B. Hillebrands
- All-linear time reversal by a dynamic artificial crystal, Nat. Commun. 1, 141 (2010)
A.V. Chumak, V.S. Tiberkevich, A.D. Karenowska, A.A. Serga, J.F. Gregg, A.N. Slavin, B. Hillebrands
- Magnonic crystal based forced dominant wavenumber selection in a spin-wave active ring, Appl. Phys. Lett. 96, 082505 (2010)
A.D. Karenowska, A.V. Chumak, A.A. Serga, J.F. Gregg, B. Hillebrands,
- Reverse Doppler effect of magnons with negative group velocity scattered from a moving Bragg grating, Phys. Rev. B 81, 140404(R) (2010)
A.V. Chumak, P. Dhagat, A. Jander, A.A. Serga, B. Hillebrands
- Spin-wave tunneling through a mechanical gap, Europhys. Lett. 90, 27003 (2010)
T. Schneider, A.A. Serga, R.L. Stamps, M.P. Kostylev, B. Hillebrands
- 6. F. Ciubotaru, A.V. Chumak, N.Yu. Grigoryeva, A.A. Serga, B. Hillebrands, Magnonic band gap design by the edge modulation of micro-sized waveguides, J. Phys. D: Appl. Phys. 45, 255002 (2012)
F. Ciubotaru, A.V. Chumak, N.Yu. Grigoryeva, A.A. Serga, B. Hillebrands
- Oscillatory energy exchange between waves coupled by a dynamic artificial crystal, Phys. Rev. Lett. 108, 015505 (2012)
A.D. Karenowska, J.F. Gregg, V.S. Tiberkevich, A.N. Slavin, A.V. Chumak, A.A. Serga, B. Hillebrands
(See online at https://doi.org/10.1103/PhysRevLett.108.015505) - Probing dynamical magnetization pinning in circular dots as a function of the external magnetic field orientation, Phys. Rev. B 86, 054419 (2012)
G.N. Kakazei, G.R. Aranda, S.A. Bunyaev, V.O. Golub, E.V. Tartakovskaya, A.V. Chumak, A.A. Serga, B. Hillebrands, K.Y. Guslienko
(See online at https://doi.org/10.1103/PhysRevB.86.054419) - Storage-recovery phenomenon in magnonic crystal, Phys. Rev. Lett. 108, 257207 (2012)
A.V. Chumak, V.I. Vasyuchka, A.A. Serga, M.P. Kostylev, V.S. Tiberkevich, B. Hillebrands
(See online at https://doi.org/10.1103/PhysRevLett.108.257207) - A micro-structured ion-implanted magnonic crystal, Appl. Phys. Lett. 102, 202403 (2013)
B. Obry, P. Pirro, T. Brächer, A.V. Chumak, J. Osten, F. Ciubotaru, A.A. Serga, J. Fassbender, B. Hillebrands
(See online at https://doi.org/10.1063/1.4807721) - Magnonic band gaps in waveguides with a periodic variation of the saturation magnetization, Phys. Rev. B 88, 134406 (2013)
F. Ciubotaru, A.V. Chumak, B. Obry, A.A. Serga, B. Hillebrands
(See online at https://doi.org/10.1103/PhysRevB.88.134406) - Magnon transistors for all-magnon data processing, Nat. Commun. 5, 4700 (2014)
A.V. Chumak, A.A. Serga, B. Hillebrands
(See online at https://doi.org/10.1038/ncomms5700) - A spin-wave logic gate based on a width-modulated dynamic magnonic crystals, Appl. Phys. Lett. 106, 102405 (2015)
A.A. Nikitin, A.B. Ustinov, A.A. Semenov, A.V. Chumak, A.A. Serga, V.I. Vasuchka, E. Lähderanta, B.A. Kalinikos, B. Hillebrands
(See online at https://doi.org/10.1063/1.4914506)
