Experimental evidences of a large extrinsic spin Hall effect in AuW alloy

We report an experimental study of a gold-tungsten alloy (7% at. W concentration in Au host) displaying remarkable properties for spintronics applications using both magneto-transport in lateral spin valve devices and spin-pumping with inverse spin Hall effect experiments. A very large spin Hall angle of about 10% is consistently found using both techniques with the reliable spin diffusion length of 2 nm estimated by the spin sink experiments in the lateral spin valves. With its chemical stability, high resistivity and small induced damping, this AuW alloy may find applications in the nearest future

Electrical spin injection and detection in Germanium using three terminal geometry

In this letter, we report on successful electrical spin injection and detection in \textit{n}-type germanium-on-insulator (GOI) using a Co/Py/Al$_{2}$O$_{3}$ spin injector and 3-terminal non-local measurements. We observe an enhanced spin accumulation signal of the order of 1 meV consistent with the sequential tunneling process via interface states in the vicinity of the Al$_{2}$O$_{3}$/Ge interface. This spin signal is further observable up to 220 K. Moreover, the presence of a strong \textit{inverted} Hanle effect points at the influence of random fields arising from interface roughness on the injected spins.Comment: 4 pages, 3 figure

Influence of ion irradiation on switching field and switching field distribution in arrays of Co/Pd-based bit pattern media

International audienceWe have used ion irradiation to tune switching field and switching field distribution ͑SFD͒ in polycrystalline Co/Pd multilayer-based bit pattern media. Light He + ion irradiation strongly decreases perpendicular magnetic anisotropy amplitude due to Co/Pd interface intermixing, while the granular structure, i.e., the crystalline anisotropy, remains unchanged. In dot arrays, the anisotropy reduction leads to a decrease in coercivity ͑H C ͒ but also to a strong broadening of the normalized SFD/ H C ͑in percentage͒, since the relative impact of misaligned grains is enhanced. Our experiment thus confirms the major role of misorientated grains in SFD of nanodevice arrays. Today a major research effort in magnetism is targeted toward achieving ultrahigh density data storage with nano-scale magnets. Spin-transfer magnetic random access memory ͑spin-RAM͒ and bit patterned media ͑BPM͒ technologies are currently part of the most promising media. The implementation of both of these technologies relies on achieving in-detail physical understanding and control of the magnetization reversal mechanism in each nanoscopic individual bit to ensure reproducibility of the bit properties in order to avoid write errors. Perpendicular magnetic anisotropy ͑PMA͒ materials, such as polycrystalline Co/Pd, Co/Pt, and Co/Ni multilayers, are believed to be promising materials for both spin-RAM and BPM applications. 1–4 Indeed, they have a well defined high amplitude uniaxial anisotropy that provides good thermal stability while offering low critical current in spin-transfer devices 2 and tunable switching fields in BPM.

Magnetic reversal in ion-irradiated FePt thin films

International audiencePrevious work on ion irradiation control of FePt thin films magnetic anisotropy is extended to ultrathin films (2-10nm). The effects of 30keV He ion irradiation on the magnetic properties are explored as a function of ion fluence and film thickness. Depending on their growth conditions, the thinnest films exhibit different magnetic properties. Although this affects their final magnetic behaviour, we show that after irradiation at 300 @BULLET C the easy magnetization axis may rotate entirely from inplane to out-of-plane at very low fluences, e.g. 2×10 13 He + /cm 2 on 5 nm thick film. This demonstrates the extreme sensitivity of the magnetic anisotropy to ion-induced local L1 0 ordering. Under these conditions, ultrathin films may exhibit perfectly square hysteresis loops with 100% remnant magnetization and low coercivity

Tuning spin-charge interconversion with quantum confinement in ultrathin bismuth films

Spin-charge interconversion (SCI) phenomena have attracted a growing interest in the field of spintronics as means to detect spin currents or manipulate the magnetization of ferromagnets. The key ingredients to exploit these assets are a large conversion efficiency, the scalability down to the nanometer scale and the integrability with opto-electronic and spintronic devices. Here we show that, when an ultrathin Bi film is epitaxially grown on top of a Ge(111) substrate, quantum size effects arising in nanometric Bi islands drastically boost the SCI efficiency, even at room temperature. Using x-ray diffraction (XRD), scanning tunneling microscopy (STM) and spin- and angle-resolved photoemission (S-ARPES) we obtain a clear picture of the film morphology, crystallography and electronic structure. We then exploit the Rashba-Edelstein effect (REE) and inverse Rashba-Edelstein effect (IREE) to directly quantify the SCI efficiency using optical and electrical spin injection.Comment: 18 pages, 5 figure

Giant magnetoresistance in lateral metallic nanostructures for spintronic applications

Abstract In this letter, we discuss the shift observed in spintronics from the current-perpendicular-to-plane geometry towards lateral geometries, illustrating the new opportunities offered by this configuration. Using CoFe-based all-metallic LSVs, we show that giant magnetoresistance variations of more than 10% can be obtained, competitive with the current-perpendicular-to-plane giant magnetoresistance. We then focus on the interest of being able to tailor freely the geometries. On the one hand, by tailoring the non-magnetic parts, we show that it is possible to enhance the spin signal of giant magnetoresistance structures. On the other hand, we show that tailoring the geometry of lateral structures allows creating a multilevel memory with high spin signals, by controlling the coercivity and shape anisotropy of the magnetic parts. Furthermore, we study a new device in which the magnetization direction of a nanodisk can be detected. We thus show that the ability to control the magnetic properties can be used to take advantage of all the spin degrees of freedom, which are usually occulted in current-perpendicular-to-plane devices. This flexibility of lateral structures relatively to current-perpendicular-to-plane structures is thus found to offer a new playground for the development of spintronic applications

Dimensionality effects on the magnetization reversal in narrow FePt nanowires

International audienceThe magnetization reversal of 10 nm thick FePt nanowires has been studied for widths down to 30 nm. Above 500 nm, the magnetic domains grow within a dendritic structure. Below 300 nm, the reversal takes place by propagation of a single domain wall (DW), and the coercivity increases. Below 50 nm, the coercivity increase is such that a mix of nucleation and DW propagation appears. These results suggest that the reversal process is determined by the comparison of the wire dimensions with four characteristic lengths: the dendrite width, the disorder length, the mean edge roughness, and the nucleation distance