Broadband excitation of spin wave using microstrip line antennas for integrated magnonic devices

Strong- and broadband-spin-wave (SW) excitation/detection structures are useful for magnonic devices. In particular, such structures are essential for observing magnonic bandgaps of magnonic crystals (MCs). Therefore, this study proposes a manufacturable broadband-SW excitation/detection antenna structure suitable for evaluating MCs. The antenna structure comprises a microstrip line fabricated on a yttrium iron garnet on a metal-covered silicon substrate. Calculations were performed using a three-dimensional finite integration technique and dispersion curves of SWs. The proposed structure exhibited high performance because of the significantly short distance between the signal line and ground plane. The generated bandwidth was ~1.69 GHz for the 8.9-μm-wavelength SW at a frequency of 4 GHz. This work proposed an appropriate antenna structure for observing magnonic bandgaps, showing high potential for the development of MCs in integrated SW devices.

Recursive evolution of spin-wave multiplets in magnonic crystals of antidot-lattice fractals

We explored spin-wave multiplets excited in a different type of magnonic crystal composed of ferromagnetic antidot-lattice fractals, by means of micromagnetic simulations with a periodic boundary condition. The modeling of antidot-lattice fractals was designed with a series of self-similar antidot-lattices in an integer Hausdorff dimension. As the iteration level increased, multiple splits of the edge and center modes of quantized spin-waves in the antidot-lattices were excited due to the fractals’ inhomogeneous and asymmetric internal magnetic fields. It was found that a recursive development (Fn = Fn−1 + Gn−1) of geometrical fractals gives rise to the same recursive evolution of spin-wave multiplets.

Engineered Magnetization Dynamics of Magnonic Nanograting Filters

Magnonic crystals and gratings could enable tunable spin-wave filters, logic, and frequency multiplier devices. Using micromagnetic models, we investigate the effect of nanowire damping, excitation frequency and geometry on the spin wave modes, spatial and temporal transmission profiles for a finite patterned nanograting under external direct current (DC) and radio frequency (RF) magnetic fields. Studying the effect of Gilbert damping constant on the temporal and spectral responses shows that low-damping leads to longer mode propagation lengths due to low-loss and high-frequency excitations are also transmitted with high intensity. When the nanowire is excited with stronger external RF fields, higher frequency spin wave modes are transmitted with higher intensities. Changing the nanowire grating width, pitch and its number of periods helps shift the transmitted frequencies over super high-frequency (SHF) range, spans S, C, X, Ku, and K bands (3–30 GHz). Our design could enable spin-wave frequency multipliers, selective filtering, excitation, and suppression in magnetic nanowires.