Measurements of the long-wavelength dispersion of spin waves along the principal directions of an yttrium iron garnet film

Historically, spin waves have been excited by two techniques: 1) a wire, stripe, or coaxial stripline [1] (which provides weak coupling but functions over a range of wavelengths that is of the order of or larger than the characteristic width dimensions of the stripes), or 2) a spatially-resonant multi-element antenna [2].
The present study focuses on a systematic investigation of the dispersion of spin waves in YIG (yttrium iron garnet, Y₃Fe₅O₁₂) that are excited using optical-lithographically patterned multi-element “ladder” antennas. A microwave current is passed through the “rungs” of this structure which then produces a spatially periodic microwave field; when coupled to an adjacent ferromagnetic film, this can excite spin waves which results in absorption peaks when the external frequency and magnetic field are such that the rung spacing, d, matches the wavelength, l, of a spin wave mode. In some cases, sub-wavelength peaks, where l = d / p and p is an integer, can be resolved.

References
[1] P. K. Amiri, B. Rejaei, M. Vroubel and Y. Zhuang, Appl. Phys. Lett. 91, 062502 (2007).
[2] J. D. Adam, R. W. Patterson and T. W. Okeeffe, J. Appl. Phys. 49, 1797 (1978).