The Sm-Fe system known as Giant magnetostrictive (GM) thin films was prepared by d.c. magnetron sputtering process. The present study has shown the importance of the energetic incidence ions onto the depositing film surface for the magnetostrictive properties. The effect of ion bombardment on the magnetostrictive characteristics of GM films was quantitatively discussed. The new parameter, ion momentum, was proposed for the design of GM films. (C) 2009 Elsevier B. V. All rights reserved.