Micro-focused Brillouin light scattering: imaging spin waves at the nanoscale

Sebastian, Thomas; Schultheiß, Katrin; Obry, B.; Hillebrands, Burkard; Schultheiß, Helmut

doi:10.3389/fphy.2015.00035

Cited by 286 publications

(232 citation statements)

References 128 publications

(167 reference statements)

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“…The technique is generally used in conjunction with a microwave excitation scheme and, over the last decade, has undergone extensive improvements. BLS spectroscopy now achieves a spatial resolution of 250 nm, and time-, phase-, and wavenumber-resolved BLS spectroscopy has been realized [3,8,[134][135][136][165][166][167].…”

Section: Detectionmentioning

confidence: 99%

“…One of the major advantages of this material is that it has a fairly low spin-wave damping value considering it is a metal, and it can be easily deposited and nanostructured [127][128][129][130][131][132][133][134]. Therefore, permalloy was intensively used for the investigation of spin-wave physics in microstructures (see reviews [135,136]) and for invest igations of magnonic crystals in particular [3,5,7,134,137]. Nowadays, considerable attention from the community is also focused on CoFeB [138][139][140][141][142] and half-metallic Heusler compounds [143][144][145][146][147][148][149][150].…”

Section: Magnetic Materials For Magnonic Applicationsmentioning

confidence: 99%

“…The most popular of the other detection techniques in magnonics nowadays is probably BLS spectroscopy [8,135,136,165]. The physical basis of BLS spectroscopy is the inelastic scattering of photons by magnons.…”

Section: Detectionmentioning

confidence: 99%

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Magnonic crystals for data processing

Chumak

Serga

Hillebrands

2017

J. Phys. D: Appl. Phys.

437

320

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IntroductionThis article focuses on a selection of results in the field of magnonic crystals obtained within the last decade in our group. Special attention is devoted to the application of magnonic crystals in data processing and information technologies. Because of the large number of achievements in the field, it is unavoidable that many important results are excluded from this article. Therefore, we would like to direct the reader's attention to excellent reviews devoted to different aspects of magnonic crystals: spin-wave dynamics in periodic structures for microwave applications [1, 2], Brillouin light scattering (BLS) studies of planar metallic magnonic crystals [3], micromagnetic computer simulations of width-modulated waveguides [4], photo-magnonic aspects of antidot lattices studies [5], theoretical studies of one-dimensional monomode waveguides [6], and reconfigurable magnonic crystals [7]. The results presented in the current review were already partially presented in our own reviews of yttrium iron garnet (YIG) magnonics [8] and magnon spintronics [9] as well as in book chapters on dynamic magnonic crystals [10] and magnon spintronics [11].The article is organized in the following way: In the introduction we describe the field of magnon spintronics and discuss the role of magnonic crystals in it. The next section 2 is devoted to the properties of spin waves in thin planar films and waveguides, to the magnetic materials commonly used in the field, and to the methods of spin-wave excitation and detection. Sections 3 and 4 are devoted to the study of physical phenomena taking place in static and dynamic magnonic crystals, respectively. The application of magnonic crystals for magnonbased processing of analog and digital data is discussed in section 5. Specifically, static magnonic crystals can be used as passive elements, like microwave filters, resonators or delay lines for microwave generation. Reconfigurable and dynamic magnonic crystals are promising as active devices performing, for example, tunable filtering, frequency conversion or time reversal. In the final section we briefly summarize the results. Magnon spintronics: from electron-to magnon-based computingA disturbance in the local magnetic order can propagate in a magnetic material in the form of a wave. This wave was first predicted by Bloch in 1929 and was named spin wave since AbstractMagnons (the quanta of spin waves) propagating in magnetic materials with wavelengths at the nanometer-scale and carrying information in the form of an angular momentum can be used as data carriers in next-generation, nano-sized low-loss information processing systems. In this respect, artificial magnetic materials with properties periodically varied in space, known as magnonic crystals, are especially promising for controlling and manipulating magnon currents. In this article, different approaches for the realization of static, reconfigurable, and dynamic magnonic crystals are presented along with a variety of novel wave phenomena discovered in these cryst...

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Section: Detectionmentioning

confidence: 99%

Section: Magnetic Materials For Magnonic Applicationsmentioning

confidence: 99%

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Magnonic crystals for data processing

Chumak

Serga

Hillebrands

2017

J. Phys. D: Appl. Phys.

437

320

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“…15 In contrast, the elastically scattered light retains its incident energy and polarization. 16,17 All of the scattered and collected light passes again the λ/2-plate before it reaches the PBS. The PBS is then used to selectively direct the inelastically scattered photons (which underwent a polarization rotation) to a Tandem-Fabry-Pérot interferometer (TFP).…”

Section: 11mentioning

confidence: 99%

Combined Brillouin light scattering and microwave absorption study of magnon-photon coupling in a split-ring resonator/YIG film system

Klingler

Maier-Flaig

Gross

et al. 2016

Applied Physics Letters

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Microfocused Brillouin light scattering (BLS) and microwave absorption (MA) are used to study magnonphoton coupling in a system consisting of a split-ring microwave resonator and a yttrium iron garnet (YIG) film. The split-ring resonantor is defined by optical lithography and loaded with a 1 µm-thick YIG film grown by liquid phase epitaxy. BLS and MA spectra of the hybrid system are simultaneously recorded as a function of the applied magnetic field magnitude and microwave excitation frequency. Strong coupling of the magnon and photon modes is found with a coupling strength of g eff /2π = 63 MHz. The combined BLS and MA data allows to study the continuous transition of the hybridized modes from a purely magnonic to a purely photonic mode by varying the applied magnetic field and microwave frequency. Furthermore, the BLS data represent an up-conversion of the microwave frequency coupling to optical frequencies.The interaction between light and magnetic matter is of long-standing and fundamental interest. In recent years, the coupling of elementary excitations of the light field (photons) to those of the spin system (magnons) regained interest due to potential applications in quantum information processing.1-3 For example, hybrid quantum system are discussed as potential candidates for the upand down-conversion of quantum signals from the optical to the microwave domain and vice versa. One way of interfacing the microwave regime is to magnetically dipole couple the spin ensemble to a microwave resonator. 4-8The prerequisite for information transfer on the quantum level is to realize a large coupling strength exceeding the loss rates of the subsytems, 4,7,9 here, the microwave resonator and the spin ensemble. Since the coupling rate is proportional to the square root of the number of participating spins 4,10 ferromagnets with a high spin density are ideal for the creation of strongly coupled, hybridized magnon-photon modes. 10,11Recently, magnon-photon coupling has been investigated in several experiments where a microwave cavity was loaded with yttrium iron garnet (YIG) and the microwave transmission and/or reflection was measured as a function of the applied magnetic field.4-7 Furthermore, spin pumping in combination with the dc inverse spin Hall effect has been employed as a detection scheme for sensing the magnonic part of magnon-photon polaritons in magnetic thin film heterostructures, 6,8 which is effectively a down-conversion of the coupling to dc.Here, we report on the up-conversion of the strong coupling of photons in a micropatterned microwave splitring resonator 12,13 (SRR) and a YIG film to optical frequencies. In particular, we use Brillouin light scattera) Electronic mail: stefan.klingler@wmi.badw.de ing (BLS) spectroscopy and microwave absorption (MA) measurements to simultaneously probe both magnonic and photonic excitations in a coupled SRR/YIG film system, which is a first step towards wavelength upconversion. We observe a clear mode anti-crossing indicating a hybridization of the magnon and micro...

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“…In the following, time-resolved Brillouin light scattering microscopy (µBLS) is employed to observe the spinwave dynamics in a spin-wave waveguide 22 . The magnetic layer of the 7 µm wide and 30 µm long waveguide is made from the low-damping Heusler compound Co 2 Mn 0.6 Fe 0.4 Si (CMFS) 23 (see Fig.…”

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confidence: 99%

Characterization of spin-transfer-torque effect induced magnetization dynamics driven by short current pulses

Meyer

Brächer

Heussner

et al. 2018

Applied Physics Letters

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We present a time-resolved study of the magnetization dynamics in a microstructured Cr|Heusler|Pt waveguide driven by the Spin-Hall-Effect and the Spin-Transfer-Torque effect via short current pulses. In particular, we focus on the determination of the threshold current at which the spin-wave damping is compensated. We have developed a novel method based on the temporal evolution of the magnon density at the beginning of an applied current pulse at which the magnon density deviates from the thermal level. Since this method does not depend on the signal-to-noise ratio, it allows for a robust and reliable determination of the threshold current which is important for the characterization of any future application based on the Spin-Transfer-Torque effect.In the last years, the field of magnon spintronics 1 has attracted prominent interest since it offers great potential to realize future logic devices. In this field, currents of magnons, the quanta of spin-waves, are used to transport and process information. Recently, a set of prototype devices has been realized such as, e.g., the magnonic majority gate 2,3 , in which the logic state of the output signal is determined by the majority of the input states. Other works on magnon based devices such as the magnon transistor 4 , the spin-wave multiplexer 5 , domain walls as spinwave nanochannels 6 , graded-index magnonics 7 or a signal splitter based on caustic-like spin-wave beams 8 pave the way towards a controlled spin-wave transfer in magnonic networks.However, the application of these devices is limited by the finite magnon lifetime and, hence, the limited magnon propagation length determined by the Gilbert damping 9 . Thus, an efficient amplification of spin-waves or a control of the effective damping is inevitable. The latter can be achieved by employing the Spin-TransferTorque effect (STT) 10 . This effect yields an additional torque on the magnetization which can be co-aligned with the Gilbert damping torque resulting in an effective spin-wave damping given by the interplay of the Gilbert damping and the STT effect. This led, e.g., to the development of spin-torque nano-oscillators based on point-contacts which allow to generate oscillations in the GHz-range by DC currents 11,12 . Furthermore, in combination with the Spin-Hall-Effect (SHE) 13 to convert a charge current into a spin current in a normal metal, the SHE-STT effect allows for the control of the effective spin-wave damping also in spatially extended magnonic devices [14][15][16][17][18][19] . To achieve large SHE-STT induced effects with minimal current densities, the use of new materials with a low spin-wave damping, such as cobalt-based Heusler compounds 20 , is very promising. Using the SHE, e.g. in a Pt layer adjacent to a cobalt-based Heusler compound, the SHE-STT effect offers a powerful link to combine magnonics with CMOS technologies.Up to now, most of the reported studies on the manipulation of spin-waves in a magnonic waveguide via the SHE-STT effect only use static DC currents or quasi-DC p...

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Micro-focused Brillouin light scattering: imaging spin waves at the nanoscale

Cited by 286 publications

References 128 publications

Magnonic crystals for data processing

Magnonic crystals for data processing

Combined Brillouin light scattering and microwave absorption study of magnon-photon coupling in a split-ring resonator/YIG film system

Characterization of spin-transfer-torque effect induced magnetization dynamics driven by short current pulses

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