The amorphous CoZrNb films were deposited by DC magnetron sputtering.The depth distributions of the elements were analyzed by Rutherford backscattering spectrometry(RBS).The results indicate that when the deposition time is longer than 37 min,the film composition keeps constant along the depth.When the deposition time is longer than 45 min,the Co concentration at the interface of the silicon substrate is higher than the average value in the whole film.When the deposition time is longer than 52 min,the Co atoms diffuse into the substrate during the deposition.According to the Co composition profile in the substrate,which were determined from the RBS spectra,the Co diffusion coefficients in the substrate were calculated using the solution of Fick′s second law corresponding to an infinite source with a constant diffusion coefficient.The calculated diffusion coefficients indicate an interstitial assisted diffusion mechanism.