Abstract
Spin wave emission and propagation in magnonic waveguides represent a highly promising alternative for beyond-CMOS computing. It is therefore all the more important to fully understand the underlying physics of the emission process. Here, we use time-resolved scanning transmission x-ray microscopy to directly image the formation process of the globally excited local emission of spin waves in a permalloy waveguide at the nanoscale. Thereby, we observe spin wave emission from the corner of the waveguide as well as from a local oscillation of a domain-wall-like structure within the waveguide. Additionally, an isofrequency contour analysis is used to fully explain the origin of quasicylindrical spin wave excitation from the corner and its concurrent nonreflection and nonrefraction at the domain interface. This study is complemented by micromagnetic simulations which perfectly fit the experimental findings. Thus, we clarify the fundamental question of the emission mechanisms in magnonic waveguides which lay the basis for future magnonic operations.
Highlights
Spin waves in ferromagnetic wires, which can be described as a collective precession of the magnetization with a spatial phase shift, are currently of high fundamental scientific interest regarding prospective technologies at the nanoscale [1,2,3,4]
There, domains of quasiperiodic ripples were detected within a polycrystalline magnonic waveguide by time-resolved scanning Kerr microscopy (TRSKM) which were excited by a global oscillating field
Besides some small defects caused by the lithography process, no ripple domains can be observed within the magnonic waveguide
Summary
Spin waves in ferromagnetic wires, which can be described as a collective precession of the magnetization with a spatial phase shift, are currently of high fundamental scientific interest regarding prospective technologies at the nanoscale [1,2,3,4]. To ensure reliability of prospective logic operations or data communication with magnons it is crucial to understand the fundamental phenomena of excitation mechanisms and propagation properties in spatially confined magnetic structures. Various concepts have been proposed which allow for an efficient excitation of spin waves in nanosized magnonic structures [7,8,9,10,11,12,13]. The placement of a magnonic crystal between a CPW and a thin film allows for bypassing
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