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arXiv · 1901.09325

Observation of band narrowing and mode conversion in two-dimensional binary magnonic crystal

Nikita Porwal·Koustuv Dutta·Sucheta Mondal·Samiran Choudhury·Jaivardhan Sinha·Anjan Barman·P. K. Datta
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Abstract

We introduce a new type of binary magnonic crystal, where Ni$_{80}$Fe$_{20}$ nanodots of two different sizes are diagonally connected forming a unit and those units are arranged in a square lattice. The magnetization dynamics of the sample is measured by using time-resolved magneto-optical Kerr effect microscope with varying magnitude and in-plane orientation ($\phi$) of the bias magnetic field. Interestingly, at $\phi=0^{\circ}$, the spin-wave mode profiles show frequency selective spatial localization of spin-wave power within the array. With the variation of $\phi$ in the range $0^{\circ}<\phi\leq 45^{\circ}$, we observe band narrowing due to localized to extended spin-wave mode conversion. Upon further increase of $\phi$, the spin-wave modes slowly lose the extended nature and become fully localized again at 90$^{\circ}$. We have extensively demonstrated the role of magnetostatic stray field distribution on the rotational symmetries obtained for the spin-wave modes. From micromagnetic simulations, we find that the dipole-exchange coupling between the nano-dots leads to remarkable modifications of the spin-wave mode profiles when compared with arrays of individual small and large dots. Numerically, we also show that the physical connection between the nano-dots provides more control points over the spin-wave propagation in the lattice at different orientations of bias magnetic field. This new type of binary magnonic crystal may find potential applications in magnonic devices such as spin-wave waveguide, filter, coupler, and other on-chip microwave communication devices.

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Nikita Porwal, Koustuv Dutta, Sucheta Mondal, Samiran Choudhury, Jaivardhan Sinha, Anjan Barman, P. K. Datta. 2019-01-27. Observation of band narrowing and mode conversion in two-dimensional binary magnonic crystal. https://doi.org/10.1016/j.jmmm.2019.166378

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