Control of Spin Waves in a Thin Film Ferromagnetic Insulator through Interfacial Spin Scattering

Wang, Zihui; Sun, Yonghe; Wu, Mingzhong; Tiberkevich, Vasil; Slavin, A. N.

doi:10.1103/physrevlett.107.146602

Cited by 129 publications

(105 citation statements)

References 17 publications

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“…The enhanced Gilbert damping of all higher transverse modes is exactly twice that of the macrospin mode. In the dipole-exchange regime, for intermediate values of QL, the dipolar interaction causes a small asymmetry in the eigenvectors for positive and negative eigenfrequencies because modes traveling in opposite directions have different magnitudes of precession near the FI/NM interface [26], and spin-pumping from these modes therefore differ. This phenomenon also explains why the enhanced damping, ∆α, splits into different branches in this regime, as shown in Fig.…”

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confidence: 99%

Spin Pumping and Enhanced Gilbert Damping in Thin Magnetic Insulator Films

Kapelrud

Brataas

2013

Phys. Rev. Lett.

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Precessing magnetization in a thin film magnetic insulator pumps spins into adjacent metals; however, this phenomenon is not quantitatively understood. We present a theory for the dependence of spin-pumping on the transverse mode number and in-plane wave vector. For long-wavelength spin waves, the enhanced Gilbert damping for the transverse mode volume waves is twice that of the macrospin mode, and for surface modes, the enhancement can be ten or more times stronger. Spinpumping is negligible for short-wavelength exchange spin waves. We corroborate our analytical theory with numerical calculations in agreement with recent experimental results. PACS numbers: 76.50.+g, 75.30.Ds, 75.76.+j, Metallic spintronics have been tremendously successful in creating devices that both fulfill significant market needs and challenge our understanding of spin transport in materials. Topics that are currently of great interest are spin transfer and spin-pumping [1][2][3], spin Hall effects [4], and combinations thereof for use in non-volatile memory, oscillator circuits, and spin wave logic devices. A recent experimental demonstration that spin transfer and spin-pumping can be as effective in magnetic insulators as in metallic ferromagnetic systems was surprising and has initiated a new field of inquiry [5].In magnetic insulators, no moving charges are present, and in some cases, the dissipative losses associated with the magnetization dynamics are exceptionally low. Nevertheless, when a magnetic insulator is placed in contact with a normal metal, magnetization dynamics induce spin-pumping, which in turn causes angular momentum to be dumped to the metal's itinerant electron system. Due to this non-local interaction, the magnetization losses become enhanced. Careful experimental investigations of spin-pumping and the associated enhanced magnetization dissipation were recently performed, demonstrating that the dynamic coupling between the magnetization dynamics in magnetic insulators and spin currents in adjacent normal metals is strong. Importantly, in magnetic insulators, an exceptionally low intrinsic damping combined with good material control has enabled the study of spin-pumping for a much larger range of wave vectors than has previously been obtained in metallic ferromagnets [5][6][7][8][9][10][11][12][13][14].In thin film ferromagnets, the magnetization dynamics are strongly affected by the long-range dipolar interaction, which has both static and spatiotemporal contributions. This yields different types of spin waves. When the in-plane wavelength is comparable to the film thickness or greater, the long-range dipolar interaction causes the separation of the spin-wave modes into three classes depending on the relative orientation of the applied external field, in relation to the film normal, and the spinwave propagation direction [15][16][17][18][19][20]. These spin waves are classified according to their dispersion and transverse magnetization distribution as forward volume magnetostatic spin waves (FVMSWs) when the external...

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confidence: 99%

Spin Pumping and Enhanced Gilbert Damping in Thin Magnetic Insulator Films

Kapelrud

Brataas

2013

Phys. Rev. Lett.

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“…1(c)]. By applying a current between the electrodes, a spin current is locally injected into the [Co/Ni] layer due to a combination of the spin Hall effect in Pt [5][6][7] and Rashba effect at the Pt/[Co/Ni] interface [8,9], resulting in magnetization auto-oscillation. We label our device the spin current auto-oscillator (SCAO).…”

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“…The possibility to induce dynamical states of nanomagnets or change their static configuration by the currentinduced spin torque (ST) [1, 2] has stimulated intense research into current-induced phenomena in magnetic systems. While the early experiments utilized spin-polarized electric currents in magnetic multilayers [3,4], recent studies focused on the effects of spin current produced due to the spin-orbit interaction (SOI) in bilayers of ferromagnets (F) with heavy nonmagnetic metals (N) [5][6][7][8]. The spin-orbit effects that contribute to the currentinduced phenomena include the spin Hall effect (SHE) originating from SOI in N, the Rashba effect [9] and the Dzyaloshinskii-Moriya interaction (DMI) [10], both originating from the broken inversion symmetry at the F/N interface.…”

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Dynamical Skyrmion State in a Spin Current Nano-Oscillator with Perpendicular Magnetic Anisotropy

2015

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We study the spectral characteristics of spin current nano-oscillators based on the Pt/[Co/Ni] magnetic multilayer with perpendicular magnetic anisotropy. By varying the applied magnetic field and current, both localized and propagating spin wave modes of the oscillation are achieved. At small fields, we observe an abrupt onset of the modulation sidebands. We use micromagnetic simulations to identify this state as a dynamical magnetic skyrmion stabilized in the active device region by spin current injection, whose current-induced dynamics is accompanied by the gyrotropic motion of the core due to the skew deflection. Our results demonstrate a practical route for controllable skyrmion manipulation by spin current in magnetic thin films. The possibility to induce dynamical states of nanomagnets or change their static configuration by the currentinduced spin torque (ST) [1, 2] has stimulated intense research into current-induced phenomena in magnetic systems. While the early experiments utilized spin-polarized electric currents in magnetic multilayers [3,4], recent studies focused on the effects of spin current produced due to the spin-orbit interaction (SOI) in bilayers of ferromagnets (F) with heavy nonmagnetic metals (N) [5][6][7][8]. The spin-orbit effects that contribute to the currentinduced phenomena include the spin Hall effect (SHE) originating from SOI in N, the Rashba effect [9] and the Dzyaloshinskii-Moriya interaction (DMI) [10], both originating from the broken inversion symmetry at the F/N interface. The DMI produces chiral effective fields that can result in nontrivial topological magnetic structures such as spirals, skyrmions and chiral domain walls [11].

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“…This spin-Hall torque can counteract damping in the ferromagnet and has been shown to switch uniform magnetization, 6-9 drive domain walls, [10][11][12] and control precessional magnetization dynamics. 7,9,[13][14][15][16][17][18][19][20][21][22][23] Despite the demonstrated utility of the spin Hall effect, there exists a wide disparity in its reported magnitude parameterized by the spin Hall angle. For example, reported spin…”

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Quantification of the spin-Hall anti-damping torque with a resonance spectrometer

Emori

Nan

Oxholm

et al. 2015

Applied Physics Letters

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We present a simple technique using a cavity-based resonance spectrometer to quantify the anti-damping torque due to the spin Hall effect. Modification of ferromagnetic resonance is observed as a function of small DC current in sub-mm-wide strips of bilayers, consisting of magnetically soft FeGaB and strong spin-Hall metal Ta. From the detected current-induced linewidth change, we obtain an effective spin Hall angle of 0.08-0.09 independent of the magnetic layer thickness. Our results demonstrate that a sensitive resonance spectrometer can be a general tool to investigate spin Hall effects in various material systems, even those with vanishingly low conductivity and magnetoresistance.

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Control of Spin Waves in a Thin Film Ferromagnetic Insulator through Interfacial Spin Scattering

Cited by 129 publications

References 17 publications

Spin Pumping and Enhanced Gilbert Damping in Thin Magnetic Insulator Films

Spin Pumping and Enhanced Gilbert Damping in Thin Magnetic Insulator Films

Dynamical Skyrmion State in a Spin Current Nano-Oscillator with Perpendicular Magnetic Anisotropy

Quantification of the spin-Hall anti-damping torque with a resonance spectrometer

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