Interference of spin waves

We have observed spin-wave interference for azimuthal modes in Permalloy rings. An understanding of interference effects of spin waves is essential if one thinks about, e.g., spin-wave logic or magnetic antidot lacttices where depending on the wave vector, coherence length and spin-wave symmetry new collective spin-wave excitations might form.

Left: Permalloy rings with an outer diameter of 2 Ám integrated to the 15 Ám wide central conductor of an optimized coplanar waveguide (CPW). A microwave current applied to the CPW excites the spin-wave modes. Right: (a) Measured absorption (black) as a function of in-plane field. Here, we focus on the so-called vortex state where no domain wall exists in the rings. Microscopic spins follow the outer edges. (b) Symmetry of the experiment: the wave vector of spin waves is separated in a radial and an azimuthal part. In azimuthal direction the circulating spin waves fulfil a quantization condition (i.e., constructive interference) giving rise to discrete mode eigenfrequencies observed in the lower branches in (a).

Publications on spin dynamics in nanostructured rings:
[1] F. Giesen, J. Podbielski, and D. Grundler: "Mode localization transition in ferromagnetic microscopic rings", Phys. Rev. B 76, 014431 (2007).
[abstract: click here]

[2] J. Podbielski, F. Giesen, and D. Grundler: "Spin-Wave Interference in Microscopic Rings", Phys. Rev. Lett. 96, 167207 (2006).
[abstract: click here]
[3] F. Giesen, J. Podbielski, T. Korn, and D. Grundler: "Multiple ferromagnetic resonance in mesoscopic permalloy rings", J. Appl. Phys. 97, 10A712 (2005).
[abstract: click here]
[4] F. Giesen, J. Podbielski, T. Korn, M. Steiner, A. van Staa, and D. Grundler: "Hysteresis and control of ferromagnetic resonances in rings", Appl. Phys. Lett. 86, 112510 (2005).
[abstract: click here]
[5] J. Podbielski, F. Giesen, M. Berginski, N. Hoyer, and D. Grundler: "Spin configurations in nanostructured magnetic rings: from DC transport to GHz spectroscopy", Superlattices and Microstructures 37, 341 (2005).
[abstract: click here]


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