Electrical spin-wave spectroscopy in nanoscale waveguides with nonuniform magnetization

Abstract

Spin wave modes in magnetic waveguides with the width down to 320 nm have been studied by electrical propagating spin-wave spectroscopy and micromagnetic simulations for both longitudinal and transverse magnetic bias fields. For longitudinal bias fields, a 1.3 GHz wide spin-wave band was observed in agreement with analytical dispersion relations for uniform magnetization. However, the transverse bias field led to several distinct bands, corresponding to different quantized width modes, with both negative and positive slopes. Micromagnetic simulations showed that, in this geometry, the magnetization was nonuniform and tilted due to the strong shape anisotropy of the waveguides. Simulations of the quantized spin-wave modes in such nonuniformly magnetized waveguides resulted in spin wave dispersion relations in good agreement with the experiments.

Lumped circuit model for inductive antenna spin-wave transducers

“…In the following, we discuss, as an example, the spectral characteristics of the spin-wave resistance and reactance of a wire antenna above a ferromagnetic CoFeB waveguide 24 , 31 , 52 – 54 with laterally uniform magnetization dynamics. The used material and geometric parameters are: saturation magnetization ; exchange constant ; Gilbert damping ; static bias field ; waveguide width ; CoFeB thickness ; and antenna width .…”

“…In recent years, numerous experiments have been conducted to study spin waves in nanoscale magnetic structures 15 , 24 , 58 – 60 . When such spin waves are excited by inductive antennas, the scaling behavior of the spin-wave impedance of the antenna–waveguide system is key to understand the experimental signals and their dependence on the device geometry and dimensions.…”

Probing Magnetic Defects in Ultra-Scaled Nanowires with Optically Detected Spin Resonance in Nitrogen-Vacancy Center in Diamond

“…Patterned magnetic nanowires (NWs) are an ideal medium for fast propagation of domain walls (DWs) or spin waves in the ever-growing field of spintronic devices. − Most importantly, NWs are a convenient architecture to obtain bistable magnetic configurations with a single magnetic easy axis and with anisotropic magnetic properties that can be adjusted by the wire geometry. For high density data storage and computation, scaled nanowires architectures (with wire widths of the order of 10 to 100 nm) are generally considered as frontrunners for emerging device concepts. ,− As an example, much research has been devoted to the engineering and control of the dynamic switching behavior of nanomagnets and magnetic NWs for memory and logic applications by manipulating the movement and positioning of DWs. Advanced characterization methods, such as magnetic force microscopy (MFM) or X-ray photoemission electron microscopy (XPEEM), have been instrumental for these studies, offering magnetic sensitivity in the sub-20 nm spatial resolution for ferromagnetic domains and additional information on the local chemistry, including oxidation states and coordination numbers for X-ray techniques. − Despite much encouraging progress in manufacturing technology, scaled NWs still host a wide range of stochastic magnetic nonuniformities and defects, which present major challenges for the control of their properties. , Here, due to the small scales involved and the potentially weak magnitudes of these defects, their physical characterization is very demanding and thus their properties and impact are not yet well understood.…”

Low-Loss Nanoscopic Spin-Wave Guiding in Continuous Yttrium Iron Garnet Films

“…Ferromagnetic metals can provide high group velocity, but their damping parameter is often large, with the exception of specific 3 d transition metal alloys , and Heusler compounds . Waveguides made of ferromagnetic metals have been studied extensively, − and because they are patterned easily, various waveguiding structures have been proposed. − Moreover, metallic waveguides allow for the use of electric currents to guide or excite , spin waves. Insulating yttrium iron garnet (YIG), on the other hand, offers ultralow Gilbert damping.…”