Seminaria

Dnia 2016-04-19 o godzinie 12:15 w sali 2011 odbędzie się seminarium, na którym prof. dr V. V. Kruglyak z Physics and Astronomy, University of Exeter, Exeter, United Kingdom, wygłosi referat pt:

Excitation and guiding of propagating spin waves in media with graded magnonic index

The wave solutions of the Landau-Lifshitz equation (spin waves) are characterised by some of the most complex and peculiar dispersion relations among all waves. For example, the spin-wave ("magnonic") dispersion can range from the parabolic law (typical for a quantum-mechanical electron) at short wavelengths to the non-analytical linear type (typical for light and acoustic phonons) at long wavelengths. Moreover, the long-wavelength magnonic dispersion has a gapand is inherently anisotropic, being naturally negative for a range of relative orientations between the effective field and the spin-wave wave vector. Non-uniformities in the effective field and magnetisation configurations enable the guiding and steering of spin waves in a deliberate manner and therefore represent landscapes of graded refractive index (graded magnonic index).¹ By analogy to the fields of graded-index photonics and transformation optics, the studies of spin waves in graded magnonic landscapes can be united under the umbrella of the graded-index magnonics theme¹ and will be reviewed in this talk. In particular, we will present our recent experimental data acquired using the time-resolved scanning Kerr microscopy (TRSKM) to demonstrate guiding and steering of spin waves in magnonic waveguides.² The data will be interpreted and supported using numerical micromagnetic simulations and analytical theory. Furthermore, we will use the theory and simulations to demonstrate how the graded magnonic index could also be used to excite propagating spin waves by effectively uniform microwave magnetic fields.³ The research leading to these results has received funding from the Engineering and Physical Sciences Research Council of the United Kingdom under projects EP/L019876/1 and EP/L020696/1 and from the European Union under projects No. 247556 (NoWaPhen) and No. 644348 (MagIC). ¹ Davies C.S., Kruglyak V.V. (2015), Low Temperature Physics, 41 (10), 760-766. ² Davies C.S. et al (2015), Physical Review B, 92 (2), 020408 (R). ³ Davies C.S. et al (2015), Applied Physics Letters, 107 (16), 162401. ⁴ Davies C.S. et al (2016), to be published.