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Spin wave excitations: coupling and damping effects in ultrathin films

Lenz, K.; Marko, D.; Strache, T.; Fassbender, J.


Spinwave excitations in thin film ferromagnets control several phenomena starting with spin transfer torque/spin pumping effects, magnetic relaxation and damping, to interlayer exchange coupling (IEC) and its temperature dependence. Most of them are accessible by ferromagnetic resonance (FMR).
There exist several quite different damping mechanisms, which might contribute to the magnetic relaxation processes following the excitation of the spin system. Using a broad range of microwave frequencies, I will show how these different relaxation channels, i.e., dissipative isotropic Gilbert damping as well as anisotropic two-magnon scattering, can be identified and disentangled by frequency and angle dependent FMR on Fe3Si Heusler alloys.
Changing the film thickness from 8 to 40 nm and slightly modifying the Fe concentration influences these relaxation channels [1]. Ion beam irradiation can be used to tailor the damping properties of Py/Ta multilayers after sample preparation [2].
FMR can also be used to study the interlayer exchange coupling. For single crystalline Ni/Cu/Co prototype trilayers the IEC’s temperature dependence was investigated [3]. It follows an effective power law AT n, n ≈ 1.5. The results clearly indicate that the dominant contribution to the temperature dependence is due to the excitation of thermal spin waves. This is corroborated by recently developed theory [4].

[1] Kh. Zakeri et al., Phys Rev. B 76, 104416 (2007).
[2] D. Markó, T. Strache, K. Lenz, J. Fassbender, and R. Kaltofen, submitted
[3] S.S. Kalarickal, X.Y. Xu, K. Lenz, W. Kuch, and K. Baberschke, Phys. Rev. B 75, 224429 (2007).
[4] S. Schwieger, J. Kienert, K. Lenz, J. Lindner, K. Baberschke, and W. Nolting, Phys. Rev. Lett. 98, 057205 (2007).

Keywords: Spin waves; Ferromagnetic Resonance; Interlayer exchange coupling

  • Invited lecture (Conferences)
    448. WE-Heraeus-Seminar: Excitement in magnetism: Spin-dependent scattering and coupling of excitations in ferromagnets, 22.-25.11.2009, Ringberg, Deutsch


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