Spin Wave Excitation and Propagation Properties in a Permalloy Film

We report ultra-low intrinsic magnetic damping in Co 25 Fe 75 heterostructures, reaching the low 10 −4 regime at room temperature. By using a broadband ferromagnetic resonance technique in out-of-plane geometry, we extracted the dynamic magnetic properties of several Co 25 Fe 75 -based heterostructures with varying ferromagnetic layer thickness. By measuring radiative damping and spin pumping effects, we found the intrinsic damping of a 26 nm thick sample to be α 0 3.18 × 10 −4 . Furthermore, using Brillouin light scattering microscopy we measured spin-wave propagation lengths of up to (21 ± 1) µm in a 26 nm thick Co 25 Fe 75 heterostructure at room temperature, which is in excellent agreement with the measured damping.Itinerant ferromagnets (FM) are advantageous for spintronic and magnonic devices. They benefit from, e.g., large magnetoresistive effects and current-induced spinorbit torques 1 . In many magneto-resistive technologies (e.g., anisotropic magnetoresistance, giant magnetoresistance, tunnel magnetoresistance) electronic conductivity is indispensable. Moreover, due to high saturation magnetization in metallic FMs, spin-wave (SW) group velocities are in general significantly higher than in insulating ferrimagnets 2-5 . High saturation magnetizations in general ease detection. Nevertheless, itinerant FMs typically have considerable magnetic damping 6,7 . This is unfavorable for many applications. For example, low damping is crucial for oscillators based on spin transfer torques and spin orbit torques as well as for achieving large spin-wave propagation lengths (SWPL) 8-10 . The need for thin film materials with low magnetic damping has triggered the interest in the insulating ferrimagnet yttrium-iron garnet (Y 3 Fe 5 O 12 , YIG) 11-13 . Although for YIG, very small total (Gilbert) damping parameters in the order of α G ≈ 10 −5 , and large SWPLs of a few tens of micrometers (up to ∼ 25 µm) in thin films (∼ 20 nm) have been reported 5,13,14 , its insulating properties and requirement for crystalline growth are challenges for large scale magnonic applications.Schoen et al. recently observed ultra-low intrinsic magnetic damping in Co 25 Fe 75 (CoFe) metallic thin films (α 0 = (5 ± 1.8) × 10 −4 ) 15 , and Krner et al. reported PLs of 5 µm − 8 µm in CoFe using time resolved scanning magneto-optical Kerr microscopy 4 . This motivated our study on sputter-deposited CoFe-based thin film heterostructures. We use broadband ferromagnetic resonance (BB-FMR) spectroscopy 16 in outa) Electronic of-plane (OOP) geometry and Brillouin light scattering (BLS) microscopy 17 and find intrinsic damping parameters in the lower 10 −4 regime as well as SWPLs of more than 20 µm. The damping is therefore comparable to YIG/heavy metal (HM) heterostructures 18 and the SWPL is comparable to that of state-of-the-art YIG thin films 5,13 . Thin film CoFe is a promising candidate for all-metal magnonic devices, as it combines low magnetic damping with good electrical conductivity and large saturation magnetization, while enabling easy fab...

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“…3 (f). From our experiments, we ex- tract a maximum SWPL of (21 ± 1) µm, well exceeding previously obtained results for FeNi alloys 42…”

Section: Forsupporting

confidence: 88%

High spin-wave propagation length consistent with low damping in a metallic ferromagnet

Flacke

Liensberger

Althammer

et al. 2019

Applied Physics Letters

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“…1-3 Especially, the spatially modulated spin configuration stabilized in the patterned ferromagnetic nanostructures is known to excite the non-uniform coherent spin precession with a spatial periodical modulation, namely, spin wave. [4][5][6][7] Owing to its fast time scale in GHz range and high compatibility with a Si-based semiconductor integrated circuits, the spin waves in ferromagnetic thin films are expected to have various potential applications in future telecommunication devices, such as a microwave filter, 8-10 oscillator, [11][12][13] and fast spin-information transportation. 14,15 In addition, the development of high-performance spin-based telecommunication devices also makes an innovation in military and security applications.…”

Section: Introductionmentioning

confidence: 99%

Stability of standing spin wave in permalloy thin film studied by anisotropic magnetoresistance effect

Yamanoi

Yokotani

Cui

et al. 2015

Journal of Applied Physics

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We have investigated the stability for the resonant spin precession under the strong microwave magnetic field by a specially developed detection method using the anisotropic magnetoresistance effect. The electrically separated excitation and detection circuits enable us to investigate the influence of the heating effect and the nonuniform spin dynamics independently. The large detecting current is found to induce the field shift of the resonant spectra because of the Joule heating. From the microwave power dependence, we found that the linear response regime for the standing spin wave is larger than that for the ferromagnetic resonance. This robust characteristic of the standing spin wave is an important advantage for the high power operation of the spin-wave device. V C 2015 AIP Publishing LLC. [http://dx.

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“…PACS numbers: 75. 30.Ds, 75.78.-n, 75.70.-i Spin waves or magnons, that is, well-defined collective propagation modes of the precession of magnetic moments in a ferromagnet, have attracted great attention due to their potential for use in information transmission media [1][2][3][4][5] . The less energy-dissipative propagation of spin waves in ferromagnets provides the breakthrough that opens up a new pathway for exploiting low-power electronic technologies.…”

mentioning

confidence: 99%

“…One of the co-planar waveguides is used to excite spin waves in the FeRh films and the reflection spectra S 11 and the transmission spectra S 21 are measured at room temperature using a vector network analyzer in in-plane magnetic fields transverse to the propagation direction of the spin waves up to 163 mT. The magnetic field geometry used allows to excite magnetostatic surface spin waves 4,5 . annealed FeRh thin films with different B2-order parameters S = 0.33 and 0.75, respectively.…”

mentioning

confidence: 99%

Transmission of spin waves in ordered FeRh epitaxial thin films

Usami

Suzuki

Itoh

et al. 2016

Applied Physics Letters

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We report on B2-ordering dependence of magnetostatic surface spin waves in ferromagnetic FeRh at room temperature. Spin waves transmit over a distance longer than 21 µm in highly ordered FeRh alloys even with relatively large spin-orbit interaction. The long-range transmission likely arises from the induced Rh moments of the ordered FeRh due to ferromagnetic exchange interaction between Fe and Rh. The results indicate a potential of using FeRh in spintronic and magnonic applications by integrating with other fascinating magnetic characteristics of FeRh such as electric field induced magnetic phase transition.PACS numbers: 75.30.Ds, Spin waves or magnons, that is, well-defined collective propagation modes of the precession of magnetic moments in a ferromagnet, have attracted great attention due to their potential for use in information transmission media 1-5 . The less energy-dissipative propagation of spin waves in ferromagnets provides the breakthrough that opens up a new pathway for exploiting low-power electronic technologies. In this perspective, spin wave propagation in ferrimagnetic insulator yttrium iron garnet 1,2 and metallic NiFe 3-5 that show very low damping of spin precession during the propagation has been investigated. Spin waves in other magnetic materials, however, have little been discussed although a number of magnetic materials have already been utilized for magnetic and spintronic applications so far.Among a variety of magnetic materials, unique magnetic properties of B2-ordered FeRh alloys are currently being researched extensively, e.g., antiferromagnetic (AFM) -ferromagnetic (FM) phase transition 6-17 accompanied by a large reduction in the resistivity 14 , an isotropic volume expansion of ∼1% at the AFM-FM phase transition 13 , giant magneto-resistance 17 , laser driven ultrafast switching of the magnetic phases 18 , and exchange bias at AFM FeRh/ferromagnetic metal interface 19,20 . Recent work also has demonstrated electric field induced AFM-FM phase transition due to strain transfer effects 21-24 , spin polarized current induced AFM-FM phase transition in FeRh 25,26 , and AFM memristers 27,28 . Such exciting magnetic properties offer an opportunity to be integrated in a vastly expanded range of spintronic applications. Despite, spin waves in FeRh has never been explored experimentally; even excitation and detection of spin waves have not been reported.In this paper, we report on excitation and detection of magnetostatic surface spin waves in ferromagnetic FeRh with different B2-ordering. B2-order parameter (S) dependence of the dispersion relationship of spin waves in FeRh epitaxial thin films is discussed. We find that the a) Electronic mail: taniyama.t.aa@m.titech.ac.jp transmission length of the spin waves is relatively long over 21 µm in highly ordered FeRh with S = 0.75. The long transmission length in the ordered FeRh is likely associated with the induced Rh moments by ferromagnetic exchange interaction between Fe and Rh in the ordered structure. From the fundamental physics poin...

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Spin Wave Excitation and Propagation Properties in a Permalloy Film

Cited by 29 publications

References 33 publications

High spin-wave propagation length consistent with low damping in a metallic ferromagnet

High spin-wave propagation length consistent with low damping in a metallic ferromagnet

Stability of standing spin wave in permalloy thin film studied by anisotropic magnetoresistance effect

Transmission of spin waves in ordered FeRh epitaxial thin films

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