The structure and composition of the Nd-Fe-B thin films deposited on Si(100) have been investigated. Films have been prepared by direct-current magnetron sputtering in pure argon and xenon sputter media separately. Deposition has been carried out keeping the substrates at room temperature and 360 degrees C. These films were subjected to the post-deposition annealing to a temperature of 600 degrees C in a vacuum of 5 x 10(-7) Torr. The stoichiometry and structure of these films were analysed and correlated to the deposition and annealing conditions. Films deposited in xenon sputter medium showed better crystalline properties than those sputtered in pure argon. This difference was attributed to the presence of reflected high-energy neutral gas particles in the argon medium. Films deposited in xenon were found to be relatively rich in boron compared with argon-sputtered films. Post-deposition annealing resulted in the interdiffusion at the interface between the film and substrate. The use of a SiO2 film as a barrier layer between the silicon substrate and the Nd-Fe-B film has been explored. Thermally grown SiO2 was found to be an effective diffusion barrier.