Thermal stability of Co–Ti multilayered neutron polarizers

Abstract Thermal stability of multilayered Co–Ti neutron optic polarizers with a period of the order of 103 A is investigated. The diffusion kinetics is determined by using the Du Mond and Youtz's method with grazing angle neutron reflectometry in the temperature range of 293–723 K. It was found that the diffusion is mainly directed from Co-layers towards the Ti-layers. The effective interdiffusion coefficient D eff of cobalt into titanium is calculated from the rate of decrease of the first reflected Bragg peak related to the artificial periodicity of the multilayer with the annealing temperature T . The temperature dependence of D eff is found to be described approximately by D eff ≈( D 0 exp (−0.25 eV/k B T )) cm 2  s −1 .