Giant enhancement of spin pumping efficiency using Fe3Si ferromagnet

Abstract

Spincurrentronics, which involves the generation, propagation and control of spin currents, has attracted a great deal of attention because of the possibility of realizing dissipation-free information propagation. Whereas electrical generation of spin currents originally made the field of spincurrentronics possible, and significant advances in spin-current devices has been made, novel spin-current-generation approaches such as dynamical methods have also been vigorously investigated. However, the low spin-current generation efficiency associated with dynamical methods has impeded further progress towards practical spin devices. Here we show that by introducing a Heusler-type ferromagnetic material, Fe 3 Si, pure spin currents can be generated about twenty times more efficiently using a dynamical method. This achievement paves the way to the development of novel spin-based devices.A central issue with respect to the practical application of spintronic devices is to establish a mechanism for highly efficient spin-current generation. 1 The development of magnetic tunnel junctions with single-crystal MgO barriers has addressed this challenge, 2,3 resulting in applications in magnetic heads and magnetoresistive random access memory. The electrical spin-injection from ferromagnetic materials (FM) into nonmagnetic materials (NM) is also in a similar situation. 4,5 The use of a tunnel barrier in order to overcome the conductance mismatch problem, 6 and the use of half-metal materials as spin injectors have also been proposed. 7 While steady progress has been made in the application of electrical methods for spin-current generation in spintronics devices, recent studies have also focused on more radical approaches such as dynamical, [8][9][10][11][12][13][14][15][16] thermal, 17 and acoustic 18 methods. These methods are expected to pave the way for a new generation of novel spintronics devices that involve no charge current. Spin pumping is a dynamical method in which a spin current is generated by a precession of the magnetization. It has been the subject of considerable interest because a spin current can be produced over a large area without the presence of a charge current, which is expected to reduce the problem of conductance mismatch. 13 Whereas, spin pumping is a promising technique for a next generation spin current devices, low efficiency of generation of pure spin current impedes further progress towards practical spin devices, unfortunately. For this reason, identifying a novel FM material that is capable of highly efficient spin injection is of the utmost importance. Here, we focus on single-crystal Fe 3 Si, which has desirable properties such as a smaller damping constant and a larger resistivity than those for Ni 80 Fe 20 (Py), the most commonly used spin source. 19 Moreover, high-quality single-crystal Fe 3 Si can be easily grown on semiconducting substrates such as Si, Ge and GaAs with atomically flat interfaces. [19][20][21] This means that Fe 3 Si can be applied to a wide variety of materials, al...

Spin Hall Magnetoresistance as a Probe for Surface Magnetization inPt/CoFe2O4Bilayers

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Silicon spintronics: Progress and challenges

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Dependence of dynamic magnetization and magneto-transport properties of FeAlSi films with oblique sputtering studied via spin rectification effect

“…In particular, NiFe, which possesses high anisotropic MR (AMR) and relatively low AHE, has been widely studied in spin-related transport phenomena such as spin Hall effect [17][18][19][20][21][22][23] (SHE) and spin torque transfer [24][25][26] (STT). It has been recently found 27 that the spin pumping efficiency in single-crystal Fe 3 Si can be up to 20 times higher than NiFe. Co-doped FeSi, a relatively high T c magnetic semiconductor, has also been found 28 to exhibit very high AHE.…”