Spin Pumping through Different Spin–Orbit Coupling Interfaces in β-W/Interlayer/Co₂FeAl Heterostructures

Abstract

Spin pumping has been considered a powerful tool to manipulate the spin current in a ferromagnetic/nonmagnetic (FM/NM) system, where the NM part exhibits large spin–orbit coupling (SOC). In this work, the spin pumping in β-W/Interlayer (IL)/Co2FeAl (CFA) heterostructures grown on Si­(100) is systematically investigated with different ILs in which SOC strength ranges from weak to strong. We first measure the spin pumping through the enhancement of effective damping in CFA by varying the thickness of β-W. The damping enhancement in the bilayer of β-W/CFA (without IL) is found to be ∼50% larger than the Gilbert damping in a single CFA layer with a spin diffusion length and spin mixing conductance of 2.12 ± 0.27 nm and 13.17 ± 0.34 nm–2, respectively. Further, the ILs of different SOC strengths such as Al, Mg, Mo, and Ta were inserted at the β-W/CFA interface to probe their impact on damping in β-W/ILs/CFA. The effective damping reduced to 8% and 20% for Al and Mg, respectively, whereas it increased to 66% and 75% with ILs of Mo and Ta, respectively, compared to the β-W/CFA heterostructure. Thus, in the presence of ILs with weak SOC, the spin pumping at the β-W/CFA interface is suppressed, while for the high SOC ILs effective damping increased significantly from its original value of β-W/CFA bilayer using a thin IL. This is further confirmed by performing inverse spin Hall effect measurements. In summary, the transfer of spin angular momentum can be significantly enhanced by choosing a proper ultrathin interface layer. Our study provides a tool to increase the spin current production by inserting an appropriate thin interlayer which is useful in modifying the heterostructure for efficient performance in spintronics devices.

Thickness-Dependent Gilbert Damping and Soft Magnetism in Metal/Co-Fe-B/Metal Sandwich Structure

“…Figure 3b shows the typical FMR spectra of the Cu(5)/Co-Fe-B(3)/Cu(5) stack detected from 4 to 18 GHz. Each FMR spectrum can be accurately fitted using the Lorentz symmetric and antisymmetric functions [13]…”

“…where is the signal intensity, H is the applied magnetic field, Hr is the resonant field, S and N are the coefficients of Lorentzian symmetric and antisymmetric parts, ΔH is the FMR linewidth, and C is the offset. The extracted ΔH presents a linear relation with f as shown in Figure 3c, which can be fitted by the following equation [13,34]:…”

“…The damping studies of yttrium-iron-garnet (YIG) films [4,10,11] and Heusler alloys [12,13] were among the hottest topics in magnetism a few decades ago. In spite of such low damping from 10 −4 to 10 −5 [10,11], the complex oxides are hard to integrate with spintronic technologies.…”

Heavy metal deposition temperature tuned spin pumping efficiency control in permalloy/tantalum bilayers

“…Spin pumping strongly depends on the choice of materials used for FM and HM layers [13][14][15][16][17]. Among these material classes permalloy (Py)/tantalum (Ta) bilayer has emerged as one of the promising heterostructure having significant spin pumping efficiency [17][18][19][20][21][22][23].…”

“…Permalloy is an extremely important spintronic material [24,25] having useful properties like high spin density, high magnetic permeability and low magnetic damping [26,27]. On the other hand Ta is being widely explored in FM/HM bilayers due to its high spin-orbit coupling that allows efficient charge current to spin current conversion and vice-versa [14][15][16][17][18][19]. Spin mixing conductance is a key parameter that is used to characterize the spin pumping efficiency.…”