Control of spin injection by direct current in lateral spin valves

The spin injection and accumulation in metallic lateral spin valves with transparent interfaces are studied using dc injection current. Unlike ac-based techniques, this allows the investigation of the effects of the direction and magnitude of the injected current. We find that the spin accumulation is reversed by changing the direction of the injected current, whereas its magnitude does not change. The injection mechanism for both current directions is thus perfectly symmetric, leading to the same spin injection efficiency for both spin types. This result is accounted for by a spin-dependent diffusion model. Joule heating increases considerably the local temperature in the spin valves when high-current densities are injected (similar to 80-105 K for 1-2x10(7) A cm(-2)), strongly affecting the spin accumulation.