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

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 ($\varphi$) of the bias magnetic field. Interestingly, at $\varphi =0^{\circ }$, the spin-wave mode profiles show frequency selective spatial localization of spin-wave power within the array. With the variation of $\varphi$ in the range $0^{\circ }<\varphi \le 45^{\circ }$, we observe band narrowing due to localized to extended spin-wave mode conversion. Upon further increase of $\varphi$, 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.

arXiv comment14 pages, 7 figures, 4 pages of supplemental materials

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Cited by in corpus (2)

• Magnetization Dynamics of Nanoscale Magnetic Materials: A Perspective
• Applications of Nanomagnets as Dynamical Systems