Spin pumping, dissipation, and direct and alternating inverse spin Hall effects in magnetic-insulator/normal-metal bilayers

Abstract

We theoretically consider the spin-wave mode-and wavelength-dependent enhancement of the Gilbert damping in magnetic insulator-normal metal bilayers due to spin pumping as well as the enhancement's relation to direct and alternating inverse spin Hall voltages in the normal metal. In the long-wavelength limit, including long-range dipole interactions, the ratio of the enhancement for transverse volume modes to that of the macrospin mode is equal to two. With an out-of-plane magnetization, this ratio decreases with both an increasing surface anisotropic energy and mode number. If the surface anisotropy induces a surface state, the enhancement can be an order of magnitude larger than for the macrospin. With an in-plane magnetization, the induced dissipation enhancement can be understood by mapping the anisotropy parameter to the out-of-plane case with anisotropy. For shorter wavelengths, we compute the enhancement numerically and find good agreement with the analytical results in the applicable limits. We also compute the induced direct-and alternating-current inverse spin Hall voltages and relate these to the magnetic energy stored in the ferromagnet. Because the magnitude of the direct spin Hall voltage is a measure of spin dissipation, it is directly proportional to the enhancement of Gilbert damping. The alternating spin Hall voltage exhibits a similar in-plane wave-number dependence, and we demonstrate that it is greatest for surface-localized modes.

Pure spin currents in magnetically ordered insulator/normal metal heterostructures

“…The first experiments tried to exploit the parametric pumping of the FMR mode to move it to higher frequencies [28]. However, as pointed out by Weiler et al, not only does inductive coupling to the microwave field lead to spurious AC contributions, but the precessing motion of the magnetization in the MOI itself also inductively couples AC voltages [28,31,32,35,40]. Despite these issues, it has been shown that this AC component is considerably larger than the DC part of spin pumping, making it relevant for future applications [40,198].…”

“…An important result of these experiments is that the interface of the MOI/NM heterostructures is as transparent as all metallic ferromagnet/NM structures, showing that pure spin current transport across the interface can be very efficient in MOI/NM systems [22]. In the early stages, spin pumping experiments mostly dealt with the time-invariant part of the injected spin current in the NM, while quite recently the time-varying part of the pure spin current has been brought into focus, as it may pave the way to high processing speeds in the THz regime [28][29][30][31][32][33][34][35][36][37][38][39][40][41][42]. Moreover, the reciprocal effect of spin pumping enables us to drive magnetization dynamics and spin waves by applying a DC charge current bias to MOI/NM systems [43][44][45][46].…”

Influence of three-magnon decays on electromotive force generation by magnetostatic surface waves in integral YIG – Pt structures

“…Второй механизм обусловлен обменным взаимодействием на интерфейсе и применительно к бегущим МСВ в структурах ЖИГ/Pt рассматривался в работах [54,55]. При этом влияние спиновой накачки на распространение ПМСВ учитывалось через граничные условия на закрепление поверхностных спинов на границе ЖИГ/Pt и проявлялось в росте потерь ПМСВ.…”

“…При этом влияние спиновой накачки на распространение ПМСВ учитывалось через граничные условия на закрепление поверхностных спинов на границе ЖИГ/Pt и проявлялось в росте потерь ПМСВ. Было показано, что в структурах на основе пленок ЖИГ с магнитной поверхностной анизотропией, характеризуемой константой 𝐾 𝑠 , связанный со спиновой накачкой параметр релаксации ∆α не зависит от толщины 𝑑 пленки ЖИГ, если выполняется условие [55]: Кривая 3 на рис. 2, a отвечает расчету зависимости 𝑘(𝑓 ) с помощью дисперсионного уравнения для ПМСВ [21]:…”

Electrical Control of Spin-Mixing Conductance in a Y3Fe5O12/ Platinum Bilayer

“…Spin currents in Y 3 Fe 5 O 12 /Platinum (YIG/Pt) bilayers have attracted much attention in the past decade due to the unique spin current transport properties in magnetic insulators and spin charge conversion in heavy metals [1][2][3][4][5][6][7][8][9][10][11][12][13][14]. Mechanisms including spin pumping at the bilayer interface [15], spin diffusion [16] and the inverse spin Hall effect in heavy metals [17], have been established to interpret the generation, transfer and conversion of spin current [18].…”