EC-11 Influence of oxidic and metallic interfaces and spacers on the magnetic damping of Permalloy thin films
Creators: Ney Verena
Lenz Kilian
Hübner Rene
Ganss Fabian
Salikhov Ruslan
Hellwig Olav
Lindner Jürgen
Ney Andreas
Publisher: name: IEEE
Year: 2025

A thorough understanding of magnetic damping in ferromagnetic materials is of importance in spintronics from both a fundamental and a practical point of view. The phenomenological Gilbert parameter α [1] in the Landau-Lifshitz equation is central to quantify the magnetic damping, which can be measured with ferromagnetic resonance (FMR). Permalloy (Py = Ni80Fe20) is one of the model systems with low magnetic damping. The ferromagnetic metal is well-understood, but surprisingly the available data for α spreads from 4-9×10−3 [2,3]. To find the reason for these variations is crucial, since an increase of α is often used as an indication for spin pumping. It has to be distinguished between influences like oxidation, roughness - two magnon processes - and real spin pumping. Here, we report on a systematic study of the temperature and frequency dependence of the FMR linewidth of Py, which was grown on typical substrates (silicon and sapphire) and capped with materials commonly used for preventing oxidation (Ta, Al, and SiOx). The resulting frequency and temperature dependence of the FMR linewidth deviates significantly from the expected Gilbert-like behavior. Unwanted non-Gilbert-like contributions appear, especially at low temperatures, and particularly for oxidic interfaces [4]. In contrast, metallic capping layers avoid non-Gilbert-like contributions. Special focus was paid to the influence of the Al spacer thickness which was varied between 1 and 10 nm [5]. In particular, Py sandwiched in between a metallic Al cap and a thin spacer layer (shown in Fig. 1), exhibits negligible inhomogeneous FMR linewidth broadening and a very small, purely Gilbert-like contribution of α = 0.0068(2) down to the lowest temperature [4,5], as shown in Fig. 2. First results on the spin pumping of these systems into Pt will also be shown.References: [1] T. L. Gilbert, IEEE Trans. Magn. 40, p.3443 (2004) [2] A. A. Starikov et al., Phys. Rev. Lett. 105, p.236601 (2010) [3] M. A. W. Schoen et al., Phys. Rev. B 95, p. 134411 (2017) [4] V. Ney et al., Phys. Rev. Materials 7, p. 124403 (2023) [5] V. Ney et al., to be submitted
A thorough understanding of magnetic damping in ferromagnetic materials is of importance in spintronics from both a fundamental and a practical point of view. The phenomenological Gilbert parameter α [1] in the Landau-Lifshitz equation is central to quantify the magnetic damping, which can be measured with ferromagnetic resonance (FMR). Permalloy (Py = Ni80Fe20) is one of the model systems with low magnetic damping. The ferromagnetic metal is well-understood, but surprisingly the available data for α spreads from 4-9×10−3 [2,3]. To find the reason for these variations is crucial, since an increase of α is often used as an indication for spin pumping. It has to be distinguished between influences like oxidation, roughness - two magnon processes - and real spin pumping. Here, we report on a systematic study of the temperature and frequency dependence of the FMR linewidth of Py, which was grown on typical substrates (silicon and sapphire) and capped with materials commonly used for preventing oxidation (Ta, Al, and SiOx). The resulting frequency and temperature dependence of the FMR linewidth deviates significantly from the expected Gilbert-like behavior. Unwanted non-Gilbert-like contributions appear, especially at low temperatures, and particularly for oxidic interfaces [4]. In contrast, metallic capping layers avoid non-Gilbert-like contributions. Special focus was paid to the influence of the Al spacer thickness which was varied between 1 and 10 nm [5]. In particular, Py sandwiched in between a metallic Al cap and a thin spacer layer (shown in Fig. 1), exhibits negligible inhomogeneous FMR linewidth broadening and a very small, purely Gilbert-like contribution of α = 0.0068(2) down to the lowest temperature [4,5], as shown in Fig. 2. First results on the spin pumping of these systems into Pt will also be shown.References: [1] T. L. Gilbert, IEEE Trans. Magn. 40, p.3443 (2004) [2] A. A. Starikov et al., Phys. Rev. Lett. 105, p.236601 (2010) [3] M. A. W. Schoen et al., Phys. Rev. B 95, p. 134411 (2017) [4] V. Ney et al., Phys. Rev. Materials 7, p. 124403 (2023) [5] V. Ney et al., to be submitted