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Spin waves are investigated in Yttrium Iron Garnet (YIG) waveguides with a thickness of 39 nm and widths ranging down to 50 nm, i.e., with aspect ratios thickness over width approaching unity, using Brillouin Light Scattering spectroscopy. The experimental results are verified by a semi-analytical theory and micromagnetic simulations. A critical width is found, below which the exchange interaction suppresses the dipolar pinning phenomenon. This changes the quantization criterion for the spin-wave eigenmodes and results in a pronounced modification of the spin-wave characteristics. The presented semi-analytical theory allows for the calculation of spin-wave mode profiles and dispersion relations in nano-structures.Spin waves and their quanta, magnons, typically feature frequencies in the GHz to THz range and wavelengths in the micrometer to nanometer range. They are envisioned for the design of faster and smaller next generational information processing devices where information is carried by magnons instead of electrons [1][2][3][4][5][6][7][8][9]. In the past, spin-wave modes in thin films or rather planar waveguides with thickness-towidth aspect ratios ar = h/w << 1 have been studied. Such thin waveguides demonstrate the effect of "dipolar pinning" at the lateral edges, and for its theoretical description the thin strip approximation was developed, in which only pinning of the much-larger-in-amplitude dynamic in-plane magnetization component is taken into account [10][11][12][13][14][15]. The recent progress in fabrication technology leads to the development of nanoscopic magnetic devices in which the width w and the thickness h become comparable [16][17][18][19][20][21][22][23]. The description of such waveguides is beyond the thin strip model of effective pinning, because the scale of nonuniformity of the dynamic dipolar fields, which is described as "effective dipolar boundary conditions", becomes comparable to the waveguide width. Additionally, both, in-plane and out-of-plane dynamic magnetization components, become involved in the effective dipolar pinning, as they become of comparable amplitude.Thus, a more general model should be developed and verified experimentally. In addition, such nanoscopic feature sizes imply that the spin-wave modes bear a strong exchange character, since the widths of the structures are now comparable to the exchange length [24]. A proper description of the spin-wave eigenmodes in nanoscopic strips which considers the influence of the exchange interaction, as well as the shape of the structure, is fundamental for the field of magnonics.In this Letter, we discuss the evolution of the frequencies and profiles of the spin-wave modes in nanoscopic waveguides where the aspect ratio ar evolves from the thin film case ar → 0 to a rectangular bar with ar → 1. Yttrium Iron Garnet (YIG) waveguides with a thickness of 39 nm and widths ranging down to 50 nm are fabricated and the quasi-ferromagnetic resonance (quasi-FMR) frequencies within them are measured using microfocused Brillouin Ligh...

The design of a microstructured, fully functional spin-wave majority gate is presented and studied using micromagnetic simulations. This all-magnon logic gate consists of three-input waveguides, a spin-wave combiner and an output waveguide. In order to ensure the functionality of the device, the output waveguide is designed to perform spin-wave mode selection. We demonstrate that the gate evaluates the majority of the input signals coded into the spin-wave phase. Moreover, the all-magnon data processing device is used to perform logic AND-, OR-, NAND-and NOR-operations.In spintronics the degree of freedom of the spin is used to transmit information. Spin and, thus, angular momentum cannot only be transmitted by electrons, but also by magnons, the quanta of the dynamic excitations of the magnetic system -spin waves. It is possible to encode information in the phase or amplitude of such spin waves and to have it transmitted through spin-wave waveguides. Moreover, the wave properties allow for efficient data processing through the exploitation of the interference between spin waves.[1-8] An important step towards the application of spin-wave devices in modern information technology is the realization of spin-wave logic gates. In this context, the majority gate is of special interest since it allows for the evaluation of the majority of an odd number of input signals, as given in Tab. I. Furthermore, not only can majority operations be performed with this gate but also AND-or OR-operations, if one input (see input 3 in Tab. I) is used as a control input. Hence, the advantage of the majority gate is its configurability and functionality.[9] In a spin-wave majority gate the phase φ of the waves is used as an information carrier (φ 0 corresponds to logic "0", logic "1" is represented by φ 0 + π). Although the idea of such majority gates was presented earlier, [9,10] no practical realization suitable for the integration into magnonic circuits has thus far been proposed.One of the main problems of a realistic spin-wave majority gate is the coexistence of different spin-wave modes with different wavelengths at a fixed frequency in the structure.[11] As a result, the output signal is given by overlaying waves of various phases and, thus, the majority function is lost. As a solution, a design which guarantees for a single-mode operation has to be used. Here, we present the design of an all-magnon majority gate and prove its functionality using numerical simulations. The width of the output waveguide has been chosen in a way such as to obtain single-mode operation. The operational characteristics of the majority gate have been studied for different phases. AND-, OR-, NAND-and NOR-operations have been demonstrated using the same * Electronic address: klingles@rhrk.uni-kl.de majority gate device.For the simulations, the material parameters of 100 nm-thick Yttrium-Iron-Garnet (

We present an experimental study of spin-wave excitation and propagation in microstructured waveguides patterned from a 100 nm thick yttrium iron garnet (YIG)/platinum (Pt) bilayer. The life time of the spin waves is found to be more than an order of magnitude higher than in comparably sized metallic structures despite the fact that the Pt capping enhances the Gilbert damping. Utilizing microfocus Brillouin light scattering spectroscopy, we reveal the spin-wave mode structure for different excitation frequencies. An exponential spin-wave amplitude decay length of 31 µm is observed which is a significant step towards low damping, insulator based micro-magnonics.