The Heusler ferromagnetic (FM) compound Co 2 FeAl interfaced with a high-spin orbit coupling non-magnetic (NM) layer is a promising candidate for energy efficient spin logic circuits. The circuit potential depends on the strength of angular momentum transfer across the FM/NM interface; hence, requiring low spin memory loss and high spin-mixing conductance. To highlight this issue, spin pumping and spin-transfer torque ferromagnetic resonance measurements have been performed on Co 2 FeAl/β-Ta heterostructures tailored with Cu interfacial layers. The interface tailored structure yields an enhancement of the effective spin-mixing conductance. The interface transparency and spin memory loss corrected values of the spin-mixing conductance, spin Hall angle and spin diffusion length are found to be 3.40 ± 0.01 × 10 19 −2 , 0.029 ± 0.003, and 2.3 ± 0.5 , respectively. Furthermore, a high current modulation of the effective damping of around 2.1 % has been achieved at an applied current density of 1 × 10 9 2 , which clearly indicates the potential of using this heterostructure for energy efficient control in spin devices. * Ankit.Kumar@angstrom.uu.se † Peter.Svedlindh@angstrom.uu.se I.

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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.

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