A. Krysztofik, L. E. Coy, P. Kuświk, K. Załęski, H. Głowiński and J. Dubowik

Applied Physics Letters 111, 192404 (2017)

We show that using maskless photolithography and the lift-off technique, patterned yttrium iron garnet thin films possessing ultra-low Gilbert damping can be accomplished. The films of 70 nm thickness were grown on (001)-oriented gadolinium gallium garnet by means of pulsed laser deposition, and they exhibit high crystalline quality, low surface roughness, and the effective magnetization of 127 emu/cm³. The Gilbert damping parameter is as low as 5x10^-4.The obtained structures have well-defined sharp edges which along with good structural and magnetic film properties pave a path in the fabrication of high-quality magnonic circuits and oxide-based spintronic devices.

Fig.1. XRD h  2h plot near the (004) reflection of structured (sample1) and plain (sample 2) YIG films. Blue arrows show clear Laue reflections of the plain film. Insets show a schematic illustration of the structured and plain films used in this study.

Graczyk, M. Zelent and M. Krawczyk     
New J. Phys. 20, 053021 (2018)     

The possibility to generate short spin waves (SWs) is of great interest in the field of magnonics nowadays.Wepresent an effective and technically affordable way of conversion of long SWs, which may be generated by conventional microwave antenna, to the short, sub-micrometer waves. It is achieved by grating-assisted resonant dynamic dipolar interaction between two ferromagnetic layers separated by some distance.Weanalyze criteria for the optimal conversion giving a semi-analytical approach for the coupling coefficient.Weshow by the numerical calculations the efficient energy transfer between layers which may be either of co-directional or contra-directional type. Such a system may operate either as a short spin wave generator or a frequency filter, moving forward possible application of magnonics.

Fig.1. Possible couplings between SWs in the bilayered structure with periodicity and the definition of characteristic values. (a) Hybridization in co-directional coupling, (b) hybridization in contra-directional coupling, (c) spatialSWamplitude distribution in the case of co-directional coupling, and (d) spatial amplitude distributions in the case of contra-directional coupling.

K. Szulc, F. Lisiecki, A. Makarov, M. Zelent, P. Kuświk, H. Głowiśski, J. W. Kłos, M. Münzenberg, R. Gieniusz, J. Dubowik, F. Stobiecki and M. Krawczyk

Phys. Rev. B 99, 064412 (2019)

We investigate experimentally and theoretically the magnetization reversal process in one-dimensional magnonic structures composed of permalloy nanostripes of the two different widths and finite length arranged in a periodic and quasiperiodic order. We showed that dipolar coupling between rectangular nanostripes is significantly reduced as compared to the analytical and numerical predictions, probably due to formation of the closure domains at the nanostripe ends. Although the main feature of the hysteresis loop is determined by different shape anisotropies of the component elements and the dipolar interactions between them, the quasiperiodic order influences the hysteresis loop by introducing additional tiny switching steps and change of the plateau width. We also showed that the dipolar interactions between nanostripes forming a ribbon can be counterintuitively decreased by reduction of the distance between the neighboring ribbons..

Fig.1. Comparison of the hysteresis loops measured with LMOKE  for Fibonacci and PS array of NSs of 5 μm length, 50 nm thickness, and 10 μm separation between the ribbons. Vertical dashed lines in the inset mark the beginning and the end of the plateau. The labels I and II (III and IV) are related to switching of the wide (narrow) NSs.

F. Tejo, A. Riveros, J. Escrig, K. Y. Guslienko and O. Chubykalo-Fesenko

Sci. Rep. 8, 6280 (2018)

We investigate the dependence of the Néel skyrmion size and stability on perpendicular magnetic field in ultrathin circular magnetic dots with out-of-plane anisotropy and interfacial Dzyaloshinskii-Moriya exchange interaction. Our results show the existence of two distinct dependencies of the skyrmion radius on the applied field and dot size. In the case of skyrmions stable at zero field, their radius strongly
increases with the field applied parallel to the skyrmion core until skyrmion reaches the metastability region and this dependence slows down. More common metastable skyrmions demonstrate a weaker
increase of their size as a function of the field until some critical field value at which these skyrmions drastically increase in size showing a hysteretic behavior with coexistence of small and large radius
skyrmions and small energy barriers between them. The first case is also characterized by a strong dependence of the skyrmion radius on the dot diameter, while in the second case this dependence is
very weak.

Fig.1. Ultrathin circular ferromagnetic (FM) nanodot on a heavy metal (HM) substrate. The Néel skyrmion magnetization profile is shown by the color map. The applied magnetic field is in the z-direction and is perpendicular to the dot plane.