Determination of the copper layer thickness in spin valves by grazing incidence X-ray fluorescence

We show that at the standard laboratory wavelength of CuKα the scattering factors of Cu and Ni_0.8Fe_0.2 are identical, thereby making it impossible to distinguish the boundary of the Cu spacer layer in a Cu/permalloy spin valve structure from grazing incidence X-ray reflectivity curves. Use of grazing incidence fluorescence, in conjunction with X-ray reflectivity provides sufficient information to control the Cu layer thickness. We demonstrate the technique on two spin valves with Cu spacer layers differing in thickness by a factor of 2.5