Sessions on Quantum Technologies (Oct 15-23)

posted on the web page …

Sessions on Magnonics and Metamaterials (Nov 14-18)

  • Authors: Pawel Gruszecki, Konstantin Guslienko, Igor Lyubchanskii, and Maciej Krawczyk
    Faculty of Physics, Adam Mickiewicz University, Uniwersytetu Poznańskiego 2, 61-614 Poznan, Poland
    Title: Spin wave beam scattering at the edge spin waves
    Abstract: Spin waves at certain conditions can be confined in particular regions of the sample, exemplary in a potential well created by the demagnetizing field near the film’s edge. Typical frequencies of the edge-localized spin waves lay below the bottom of the spin wave spectrum. Here, we study theoretically dynamics of spin waves localized at the edge of thin permalloy film and their influence on the reflection of spin wave beams incident at the edge.

  • Authors: A. Krysztofik1, S. Özoğlu2, E. Coy2, J. Dubowik1
    1. Institute of Molecular Physics, Polish Academy of Sciences, Poznan, Poland
    2. NanoBioMedical Centre, A. Mickiewicz University, Poznan, Poland
    Title: Damping and Magnetic Anisotropy of YIG Thin Films Deposited on Different Substrates
    Abstract:Yttrium Iron Garnet (YIG) is one of the most desirable material for spintronic and magnonic applications mainly due to the lowest achievable damping of magnetization precession. Its growth on Gadolinium Gallium Garnet (GGG) as a substrate has been well established with different deposition techniques in past few years. However, the choice of any other substrate remains challenging when the aim is not to compromise YIG damping and improve integration with current technologies. Here, we present the results of broadband ferromagnetic resonance measurements of YIG films deposited on GGG, Yttrium Aluminum Garnet (YAG) and Si substrates, as a preliminary step towards their compatibility with prevalent CMOS technology.
    A. K. acknowledges the support from program POWR.03.02.00-00-I032/16.

  • Authors: O. Busel, S. Mieszczak, P. Gruszecki, J. W. Kłos, M. Krawczyk
    1. Faculty of Mathematics and Physics, National Technical University of Ukraine “Igor Sikorsky Kyiv Polytechnic Institute”, Prospect Peremohy 37, Kyiv, 03056, Ukraine
    2. Faculty of Physics, Adam Mickiewicz University in Poznań, ul. Uniwersytetu Poznańskiego 2, Poznań, 61-614, Poland
    Title: Spin-wave phase change via resonant scattering in magnetic spacer
    Abstract: An analytical theory of the spin waves (SWs) propagation through a ferromagnetic layer of finite width (spacer) in the direction of SWs propagation embedded in a ferromagnetic medium has been developed. The analytical results have been compared to the results of the micromagnetic simulations performed with the aid of Mumax3 package. Perfect agreement with the analytical results have been obtained. The resonant characteristic of the Fabry¬Perot type of transmission in the considered system has been shown. Based on the phase change of the transmitted SWs in dependence on the interface parameters the interface has been designed to obtain an anomalous refraction of SWs, namely, a device which effectively turns the direction of SWs propagation. With micromagnetic simulations it has been shown that exploiting the phase change between two neighboring resonances is sufficient to design the interface which allows for refraction of the incident SWs at any angle, keeping relatively high intensity of the transmitted wave. Our findings open the route for the design of flat metasurfaces for magnonic applications.

  • Authors: Justyna Rychły, V. S. Tkachenko, J. W. Kłos, A. N. Kuchko, and M. Krawczyk
    Institute of Molecular Physics, Polish Academy of Sciences, Poznań,
    Poland Faculty of Physics, Adam Mickiewicz University in Poznań, Poland
    Title: Spin waves spectrum in ferromagnetic nanowire of cylindrical cross-section
    Abstract: Nanoscale magnetic systems have been studied extensively in various geometries, such as wires of different cross sections, arrays of wires, dots, rings, etc. Such systems have promising applications in advanced magnetic devices [1]. Among them uniform magnetic nanowires are the basic structures which were investigated in the past [2,3]. However, some of their dynamical properties, like: (i) (anti)crossing between the spin wave modes and (ii) impact of magnetic field of spin wave spectrum, still need detailed studies. In our research we continue this direction and study spin wave dynamics in Ni nanowire of circular cross section. To that end we use two approaches: semi-analytical calculations and numerical calculations with the use of the finite element method. We solve Landau-Lifshitz and Maxwell equations and consider both magnetostatic and exchange interactions. We obtain spin wave dispersion relation complemented with the spatial profiles of: (i) magnetostatic potential and (ii) complex amplitudes of selected spin wave modes.
    [1] V. Chumak, et al, Nature Phys. 15, 453 (2015)
    [2] R. Arias, D.L. Mills, Phys. Rev. B, 63, 134439 (2001)
    [3] T. M. Nguyen, M. G. Cottam, Phys. Rev. 72, 224415 (2005)

  • Authors: K. Szulc1,1 G. Gubbiotti2 M. Mruczkiewicz3 and M. Krawczyk1
    1. Faculty of Physics, Adam Mickiewicz University in Poznan, Uniwersytetu Poznańskiego 2, 61-614 Poznań, Poland
    2. Istituto Officina dei Materiali del Consiglio Nazionale delle Ricerche (IOM-CNR), Perugia I-06123, Italy
    3. Institute of Electrical Engineering, Slovak Academy of Sciences, Dubravska cesta 9, 841 04 Bratislava, Slovakia
    Title: Dzyaloshinskii-Moriya interaction in bilayers with perpendicular magnetic anisotropy
    Abstract: Dzyaloshinskii-Moriya interaction (DMI) is of large interest in magnonics due to its nonreciprocal character. Its stronger variant appears at the interfaces of ultrathin ferromagnetic layer with heavy metal. Additionally, in the case of these thin films also perpendicular magnetic anisotropy can play significant role and can lead to change of the spin wave propagation and even the magnetization direction. We studied experimentally multilayers composed of Pt/Co/W and Pt/Co/Ta/Co/Pt using Brillouin light scattering method and magneto-optical Kerr effect microscopy to analyze the magnetization configuration and dispersion relation. In Pt/Co/W structures with Co layer thickness under 2 nm we observe out-of-plane magnetization in the absence of the external magnetic field. Dispersion relations show linear dependences around zero wavevector with the slope resulting from DMI. In Pt/Co/Ta/Co/Pt multilayer, reversed alignment of Co/Pt bilayers leads to opposite sign of DMI parameter. Numerical analysis shows, that in all structures the spin wave frequencies are significantly decreased due to the perpendicular magnetic anisotropy and the DMI parameter reaches 1 mJ/m2.
    This study was partially supported by National Science Center of Poland project Metasel UMO-2015/17/B/ST3/00118.

  • Authors: V. Babacic, J. Varghese, M. Pochylski, E. Kang, J. Gapinski, G. Fytas and B. Graczykowski
    1. Faculty of Physics, Adam Mickiewicz University, Uniwersytetu Poznańskiego 2, 61-614 Poznan, Poland
    2. NanoBioMedical Centre, Adam Mickiewicz University, ul. Umultowska 85, PL-61614 Poznan, Poland
    Title: Nanoscale cold soldering of coloidal phononic crystals by high pressure
    Abstract: Colloidal crystals realized by self-assembled polymer nanoparticles have prominent attraction as a platform for applications from assembling photonic and phononic crystals to organic electronics, surface coatings to drug delivery systems. In this work we report mechanical reinforcement of polystyrene colloidal crystals by means of “cold soldering” that results from nanoscale plasticization at high hydrostatic pressure of N2 and Ar. We employed Brillouin light scattering to monitor the mechanical vibrations of the crystal and thereby determine preferential conditions for soldering, i.e., formation of physical bonding among the nanoparticles while maintaining the shape and translational order of the nanoparticles.

  • Authors: Mateusz Zelent
    Faculty of Physics, Adam Mickiewicz University, Uniwersytetu Poznańskiego 2, 61-614 Poznan, Poland
    Title: Design of a spin-wave flat lens
    Abstract: In this work, we show that the phase shift of the spin waves can be controlled in transmission through metasurface formed by an ultra-narrow non-magnetic spacer separating two ferromagnetic films. For this purpose, we exploit the strength of the interlayer exchange coupling interactions of Ruderman-Kittel-Kasuya-Yosida type which allows to control the phase of the transmitted spin waves in the wide range of angles [−/2;/2]. We combined the phase-shift dependency along the interface with the lens equation to demonstrate numerically the lens for spin waves based on this ultra-narrow metasurface.