Influence of interface alloy formation on the magnetic and structural properties of Co/Si (100) thin films

In the present work, the magnetic and structural characterization of Co (20 nm)/Si thin films annealed at different temperatures has been reported. The structural measurements using X-ray diffraction and X-ray reflectivity showed an intermixing between Co and Si layers forming an interfacial CoSi_x alloy upon annealing, which transforms into complete alloy layer at 800 ºC. The magnetic measurements also confirmed this intermixing by showing a transformation of hysteresis loops from ferromagnetic-like (up to 600 ºC) signature loop of magnetic Co to paramagnetic (at 800 ºC) hysteresis loop of CoSi_x alloy. Overall results are interpreted in terms of annealing induced intermixing between Co and Si which promotes diffusion of Si atoms into Co layer and vice versa thereby deteriorating the magnetic properties of the Co film.