Reduction of spin-flip scattering in metallic nonlocal spin valves

Abstract

Cobalt-copper nonlocal spin valves are fabricated by shadow evaporation through nanoscale masks. The thickness of Co electrodes is varied and the spin diffusion length of the Cu channel is determined. Short spin diffusion lengths are found in devices with thick ͑Ͼ20 nm͒ Co layers. Co impurities are introduced into the Cu channel in the shadow evaporation process during the fabrication, and the impurities cause spin-flip scattering. The amount of Co impurities can be reduced by decreasing the thicknesses of Co electrodes. Spin diffusion lengths of ϳ400 nm at 295 K and ϳ800 nm at 4.2 K are measured in devices with thin ͑Ͻ10 nm͒ Co layers.

Temporal evolution of spin accumulation in nonlocal spin valves

“…Therefore l s gradually increases from $300 to $350 nm. The value of l s of 350 nm after 50 day exposure to air is close to the value of l s (350-400 nm at 295 K) obtained in NLSV structures made with thin Co layers [17], where the Co impurities should be minimized. Similar temporal evolutions of spin signals are observed in other two sets of devices.…”

“…These impurity atoms induce spin-flip scatterings of conduction electrons, thereby reducing the spin diffusion length of Cu. We have shown that l s of Cu can be increased from 250 to $ 400 nm (at 295 K) by reducing the thickness of the Co layers of the NLSV [17]. A thinner Co layer implies less Co accumulation on the side-walls of the resist and therefore less impurities implanted in the device.…”

Spin Hall effects in mesoscopic Pt films with high resistivity

“…For each sample, all structures on the substrate are formed simultaneously by depositing Pt, Py, AlOx, and Cu from different angles through a set of mesoscopic suspended shadow masks, which are created by electron beam (e-beam) lithography from two layers of e-beam resists: the PMGI (polydimethylglutarimide) resist on the bottom and the PMMA (polymethyl methacrylate) resist on the top. Details of the shadow mask and angle deposition method can be found elsewhere [3,[27][28][29].…”

“…For each sample, all structures on the substrate are formed simultaneously by depositing Pt, Py, AlOx, and Cu from different angles through a set of mesoscopic suspended shadow masks, which are created by electron beam (e-beam) lithography from two layers of e-beam resists: the PMGI (polydimethylglutarimide) resist on the bottom and the PMMA (polymethyl methacrylate) resist on the top. Details of the shadow maskand angle deposition method can be found elsewhere[3,[27][28][29].The measurements of the 6 samples have been carried out either in a variable temperature probe station or in a pulse-tube variable temperature cryostat. All measurements are conducted at 10 K. The SHE and ISHE measurements from a structure with 6 nm Pt are shown inFig 2 (a) and (b), respectively, and the corresponding measurement configurations are shown in the insets.…”

Absence of high surface spin-flip rate in mesoscopic silver channels

“…11,13,14) Our previous work indicates that the origin of the high surface spin-flip rate is the magnetic impurities located near the side surfaces of the nonmagnetic channel. 11,16,17) Another study 18) suggests a different origin of Kondo effects, which are also interestingly attributed to magnetic impurities in the nonmagnetic channel.…”