Magnetic damping in poly-crystalline Co25Fe75: Ferromagnetic resonance vs. spin wave propagation experiments

Abstract

We report on the investigation of the magnetic damping of a 10 nm thin, poly-crystalline Co 25 Fe 75 film grown by molecular beam epitaxy. Ferromagnetic resonance (FMR) measurements reveal a low intrinsic magnetic damping a FMR int ¼ ð1:560:1Þ Â 10 À3 . In contrast, in patterned micrometer wide stripes, spin wave (SW) propagation experiments performed by time resolved scanning magneto-optical Kerr microscopy yield attenuation lengths on the order of 5-8 lm. From this quantity, we deduce an effective magnetic SW damping a SW; exp eff ¼ ð3:960:3Þ Â 10 À3 . For the system studied, this significant difference between both damping parameters is attributed to the nonnegligible extrinsic contributions (local inhomogeneities and two-magnon scattering) to the magnetic losses which manifest themselves as a distinct inhomogeneous FMR linewidth broadening. This explanation is supported by micromagnetic simulations. Our findings prove that polycrystalline Co 25 Fe 75 represents a promising binary 3d transition metal alloy to be employed in magnonic devices with much longer SW attenuation lengths compared to other metallic systems.

Co25Fe75Thin Films with Ultralow Total Damping of Ferromagnetic Resonance

“…One means to exclude the spin pumping contributions is epitaxial growth on insulating or semiconducting substrates. Indeed, two recent studies reported the growth of Co25Fe75 on MgO and MAO resulting in values of the damping parameters around 0.001 [11,12]. Removing the constraint of epitaxial growth on single crystalline substrates while maintaining low magnetic damping and high film uniformity may enable integration of this material in a wide range of spintronic and magnonic devices [1,2].…”

Advances in Magnetics Roadmap on Spin-Wave Computing

“…The data were experimentally obtained by Brillouin light scattering in the magnetostatic surface wave configuration in a Co25Fe75 magnonic conduit with a width of 5 µm and a thickness of 26 nm for an external magnetic field magnitude of 43 mT. The combination of high group velocity and record low intrinsic damping 𝛼 < 0.001 [65] results in experimentally observed spin-wave propagation lengths [70] Achievement of these high spin-wave propagation lengths requires suppression of two-magnon scattering and inhomogeneous relaxation effects [71].…”

Spin-Wave Propagation in Metallic Co$_{25}$Fe$_{75}$ Films Determined by Microfocused Frequency-Resolved Magneto-Optic Kerr Effect

“…Although this technique is versatile and powerful due to its phase-resolving capability and frequency accuracy, it is not able to capture the magnetization dynamics locally or in micro-structured devices. In patterned devices, magnetization dynamics are locally probed by optical techniques, such as the microfocused time-resolved magneto-optic Corresponding author: L. Liensberger (Lukas.Liensberger@wmi.badw.de) Kerr effect (µTR-MOKE) [12], [13], [14] or microfocused Brillouin Light Scattering (µBLS) [15], [16].…”