Unidirectional anisotropy in the spin pumping voltage in yttrium iron garnet/platinum bilayers

Vilela-Leão, L. H.; Salvador, C.; Azevedo, A.; Rezende, S. M.

doi:10.1063/1.3631683

Cited by 54 publications

(23 citation statements)

References 20 publications

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“…This effect depends on the relative orientation between magnetization and current direction, and has recently been called spin Hall magnetoresistance (SMR) 8 . Experimental studies on spin pumping induced inverse spin Hall voltages (V ISH ) in FM|NM bilayers were first carried out with Pt as NM in combination with NiFe as FM 5,[9][10][11][12] and more recently with the insulating ferrimagnet Yttrium Iron Garnet (YIG) 6,[13][14][15][16][17] . Although other strong spin-orbit metals have been tried in combination with the metallic ferromagnets NiFe 18,19 and CoFeB 20,21 , inverse spin Hall voltage 6,17 and magnetoresistance 8,22 measurements made on YIG|NM have so far been limited to NM=Pt.…”

Section: Introductionmentioning

confidence: 99%

Comparative measurements of inverse spin Hall effects and magnetoresistance in YIG/Pt and YIG/Ta

Hahn

Loubens²,

Klein³

et al. 2013

Phys. Rev. B

479

418

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We report on a comparative study of spin Hall related effects and magnetoresistance in YIG|Pt and YIG|Ta bilayers. These combined measurements allow to estimate the characteristic transport parameters of both Pt and Ta layers juxtaposed to YIG: the spin mixing conductance G ↑↓ at the YIG|normal metal interface, the spin Hall angle ΘSH, and the spin diffusion length λ sd in the normal metal. The inverse spin Hall voltages generated in Pt and Ta by the pure spin current pumped from YIG excited at resonance confirm the opposite signs of spin Hall angles in these two materials. Moreover, from the dependence of the inverse spin Hall voltage on the Ta thickness, we extract the spin diffusion length in Ta, found to be λ Ta sd = 1.8 ± 0.7 nm. Both the YIG|Pt and YIG|Ta systems display a similar variation of resistance upon magnetic field orientation, which can be explained in the recently developed framework of spin Hall magnetoresistance.

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Section: Introductionmentioning

confidence: 99%

Comparative measurements of inverse spin Hall effects and magnetoresistance in YIG/Pt and YIG/Ta

Hahn

Loubens²,

Klein³

et al. 2013

Phys. Rev. B

479

418

View full text Add to dashboard Cite

show abstract

“…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].…”

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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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“…[4][5][6][7] The experimental demonstration that spin transfer and spin pumping are also active in normal metals in contact with insulating ferromagnets has generated a renewed interest in and refocused attention on insulating ferromagnets, of which yttrium iron garnet (YIG) continues to be the prime example. [8][9][10][11][12][13][14][15][16][17][18][19] In ferromagnetic insulators, currentinduced spin-transfer torques from a neighboring normal metal (NM) that exhibits out-of-equilibrium spin accumulation may manipulate the magnetization of the insulator and excite spin waves. 8,20,21 The out-of-equilibrium spin accumulation of the normal metal may be induced via the spin Hall effect or by currents passing through other adjacent conducting ferromagnets.…”

Section: Introductionmentioning

confidence: 99%

Spin waves in ferromagnetic insulators coupled via a normal metal

Skarsvåg¹,

Kapelrud²,

Brataas³

2014

Phys. Rev. B

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Herein, we study the spin-wave dispersion and dissipation in a ferromagnetic insulator-normal metal-ferromagnetic insulator system. Long-range dynamic coupling because of spin pumping and spin transfer lead to collective magnetic excitations in the two thin-film ferromagnets. In addition, the dynamic dipolar field contributes to the interlayer coupling. By solving the Landau-LifshitzGilbert-Slonczewski equation for macrospin excitations and the exchange-dipole volume as well as surface spin waves, we compute the effect of the dynamic coupling on the resonance frequencies and linewidths of the various modes. The long-wavelength modes may couple acoustically or optically. In the absence of spin-memory loss in the normal metal, the spin-pumping-induced Gilbert damping enhancement of the acoustic mode vanishes, whereas the optical mode acquires a significant Gilbert damping enhancement, comparable to that of a system attached to a perfect spin sink. The dynamic coupling is reduced for short-wavelength spin waves, and there is no synchronization. For intermediate wavelengths, the coupling can be increased by the dipolar field such that the modes in the two ferromagnetic insulators can couple despite possible small frequency asymmetries. The surface waves induced by an easy-axis surface anisotropy exhibit much greater Gilbert damping enhancement. These modes also may acoustically or optically couple, but they are unaffected by thickness asymmetries.

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Unidirectional anisotropy in the spin pumping voltage in yttrium iron garnet/platinum bilayers

Cited by 54 publications

References 20 publications

Comparative measurements of inverse spin Hall effects and magnetoresistance in YIG/Pt and YIG/Ta

Comparative measurements of inverse spin Hall effects and magnetoresistance in YIG/Pt and YIG/Ta

Spin Pumping and Enhanced Gilbert Damping in Thin Magnetic Insulator Films

Spin waves in ferromagnetic insulators coupled via a normal metal

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