Spin transport enhancement by controlling the Ag growth in lateral spin valves

Abstract

The role of the growth conditions in the spin transport properties of silver (Ag) have been studied by using lateral spin valve structures. By changing the deposition conditions of Ag from polycrystalline to epitaxial growth, we have observed a considerable enhancement of the spin diffusion length, from ! !" = 449 ± 30 to 823 ± 59 nm. This study shows that diminishing the grain boundary contribution to the spin relaxation mechanism is an effective way to improve the spin diffusion length in metallic nanostructures.A new generation of spintronic devices, which rely only on the electron spin degree of freedom, are envisioned towards a future integration of logics and memory [1]. Creation, transport and detection of a pure spin current, i.e., a flow of spin angular momentum without being accompanied by a charge current, are thus essential ingredients for a successful device. Lateral spin valves (LSVs) are basic spintronic devices that offer an attractive means to study the spin transport as well as the spin injection properties in different materials. After the pioneering studies, first by Johnson and Silsbee [2,3] and more recently by Jedema et al. [4,5], a large number of spin injection experiments have been reported in metals [6][7][8][9][10][11][12][13][14][15][16][17][18][19][20][21][22], semiconductors [23,24] or carbon-based materials [25,26]. LSVs consist of two ferromagnetic (FM) electrodes, used to inject and detect pure spin currents, bridged by a non-magnetic (NM) channel, which transports the injected spin current (see Fig. 1(a)). For the optimum performance of a LSV, it is crucial to choose a NM material in which the spin information can travel over long distances, i.e. with long spin diffusion length λ NM , with Cu [4-12], Al [2,5,9,13,14] or Ag [15][16][17][18][19][20][21][22] being the most commonly selected metals. In order to enhance λ NM , it is crucial to understand which are the spin relaxation processes that lead to the loss of spin information. It is known that, in NM metals, the spin relaxation is governed by the Elliott-Yafet (EY) mechanism [27,28], with phonons, grain boundaries, impurities or the surface being common sources for the associated spin-flip scattering [5,7,12,18,19]. A proper control of these contributions could thus help obtaining longer λ NM values.In this work, we explore a way of diminishing the grain boundary contribution to the spin relaxation by controlling the growth conditions of Ag. For this purpose, we have

Modulation of spin accumulation by nanoscale confinement using electromigration in a metallic lateral spin valve

“…The results of the fitting are in good agreement with previous work using similar Cu thickness [8,11]. To extract such information, usually a series of devices with varying L are needed [8,10,11,12,14,17,18,24], while in the current approach, the relevant parameters can be extracted from a single device. Hanle measurements, which can be used to extract the same information using a single device [15], are very sensitive to device details and its liability has been recently put into question [30,31,32,33].…”

Recent Progress in Simple and Cost‐Effective Top‐Down Lithography for ≈10 nm Scale Nanopatterns: From Edge Lithography to Secondary Sputtering Lithography

“…Secondary sputtering refers to a phenomenon in which substrate material particles are torn off due to the physical impact of the accelerated plasma ions and the particles are emitted at various angles with a wide angular distribution (Figure 5a). [76,[154][155][156][157] The angle of the particles deviating from the physical impact of the accelerated ions during the ion-bombardment process can be mainly controlled by the acceleration voltage intensity, the type (size) of the accelerated ions, the type of target material, and the angle of incidence. After fabricating the prepattern on the target substrate layer, if the ion-bombardment process is performed, the particles of bottom layer etched by the accelerated plasma ions are uniformly deposited on the side surface of prepattern ( Figure 5b).…”

“…Repeatable SSL showed that SSL can create precise and accurate multidirectional patterns including grids and connected Olympic-ring shaped cylinders from single line and single pillar pattern shaped master patterns by performing the additional SSL fabrication process at a specific angle on the already fabricated SSL patterns. [154] Figure 8a,c shows SEM images for fabrication of various 3D nanostructures with multifeature shapes (Figure 8a), multilayer (Figure 8b), and false-colored SEM images of multicomponent three-way grid patterns with three different materials (Figure 8c). In the center image of Figure 8a, highly precise, uniform, large concentric ring-shaped structures ≈15 nm wide were prepared from a microsized concentric PS nanostructures via the first SSL process.…”

Spin diffusion length associated with out-of-plane conductivity of Pt in spin pumping experiments

“…A NiFe(20 nm)/Ag(2 nm) reference sample was also deposited under the same conditions. As the reported value of λ s for Ag is approximately 450 nm [28], we can confidently neglect spin attenuation effects in this reference sample. The samples were finally annealed in situ at 500 K for 1 h in vacuum.…”