P. Laczkowski

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 molybdenum disulfide multilayer channel

Molybdenum disulfide has recently emerged as a promising two-dimensional semiconducting material for nano-electronic, opto-electronic and spintronic applications. However, the demonstration of an electron spin transport through a semiconducting MoS2 channel remains challenging. Here we show the evidence of the electrical spin injection and detection in the conduction band of a multilayer MoS2 semiconducting channel using a two-terminal spin-valve configuration geometry. A magnetoresistance around 1% has been observed through a 450 nm long, 6 monolayer thick MoS2 channel with a Co/MgO tunnelling spin injector and detector. It is found that keeping a good balance between the interface resistance and channel resistance is mandatory for the observation of the two-terminal magnetoresistance. Moreover, the electron spin-relaxation is found to be greatly suppressed in the multilayer MoS2 channel with an in-plane spin polarization. The long spin diffusion length (approximately ∼235 nm) could open a new avenue for spintronic applications using multilayer transition metal dichalcogenides.

In-plane and out-of-plane spin precession in lateral spin-valves

The spin signal variations of Al/NiFe lateral spin-valves with AlOx interfaces are studied under different applied field orientations. For applied fields perpendicular to the sample plane, the spin signal is governed by the spin precession and by the angular dephasing of spins in the channel, i.e., the Hanle effect. We show that using narrow permalloy wires with large shape anisotropies, it is also possible to observe spin precession with in-plane magnetic fields. In this case, the precessing spin current possesses an out-of plane component, which means that by tuning properly the external field it is possible to control along the three dimensions the orientation of the spins arriving on the ferromagnetic detector. Finally, fits of our data allow for both in and out-of plane fields extracting the relevant characteristics of our lateral spin-valves.

Switchable spin-current source controlled by magnetic domain walls.

Using nonlocal spin injection, spin-orbit coupling, or spincaloritronic effects, the manipulation of pure spin currents in nanostructures underlies the development of new spintronic devices. Here, we demonstrate the possibility to create switchable pure spin current sources, controlled by magnetic domain walls. When the domain wall is located at a given point of the magnetic circuit, a pure spin current is injected into a nonmagnetic wire. Using the reciprocal measurement configuration, we demonstrate that the proposed device can also be used as a pure spin current detector. Thanks to its simple geometry, this device can be easily implemented in spintronics applications; in particular, a single current source can be used both to induce the domain wall motion and to generate the spin signal.

Comparison of the use of NiFe and CoFe as electrodes for metallic lateral spin valves

Spin injection and detection in Co60Fe40-based all-metallic lateral spin valves have been studied at both room and low temperatures. The obtained spin signals amplitudes have been compared to those of identical Ni80Fe20-based devices. The replacement of Ni80Fe20 by CoFe allows increasing the spin signal amplitude by up to one order of magnitude, thus reaching 50 mΩ at room temperature. The spin signal dependence with the distance between the ferromagnetic electrodes has been analyzed using both a 1D spin-transport model and finite element method simulations. The enhancement of the spin signal amplitude when using CoFe electrodes can be explained by a higher effective polarization.

Elementary depinning processes of magnetic domain walls under fields and currents

The probability laws associated to domain wall depinning under fields and currents have been studied in NiFe and FePt nanowires. Three basic domain wall depinning processes, associated to different potential landscapes, are found to appear identically in those systems with very different anisotropies. We show that these processes constitute the building blocks of any complex depinning mechanism. A Markovian analysis is proposed, that provides a unified picture of the depinning mechanism and an insight into the pinning potential landscape.

Evaluation of spin diffusion length of AuW alloys using spin absorption experiments in the limit of large spin-orbit interactions

The knowledge of the spin diffusion length

Evidence for spin-to-charge conversion by Rashba coupling in metallic states at the Fe/Ge(111) interface

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Using domain walls to perform non-local measurements with high spin signal amplitudes

is a prerequisite for the estimation of the spin Hall angle. We investigate spin current absorption of materials with small

Spin–Charge Conversion Phenomena in Germanium

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