We have investigated experimentally the nonlocal voltage signal (NLVS) in the lateral Permalloy $\left(\mathrm{Py}\right)∕\mathrm{Cu}∕\mathrm{Py}$ spin-valve devices with different width of Cu stripes. We found that NLVS strongly depends on the distribution of the spin-polarized current inside Cu strip in the vicinity of the Py detector. To explain these data we have developed a diffusion model describing spatial (three dimensional) distribution of the spin-polarized current in the device. The results of our calculations show that NLVS is decreased by a factor of 10 due to spin flip scattering occurring at the $\mathrm{Py}∕\mathrm{Cu}$ interface. The interface resistivity on the $\mathrm{Py}∕\mathrm{Cu}$ interface is also present, but its contribution to reduction of NLVS is minor. We also found that most of the spin-polarized current is injected within the region $30\mathrm{nm}$ from the Py injector/Cu interface. In the area at Py detector/Cu interface, the spin-polarized current is found to flow mainly close on the injector side, with $1∕e$ exponential decay in the magnitude within the distance $80\mathrm{nm}$.

• Received 15 July 2004

DOI:https://doi.org/10.1103/PhysRevB.71.094402