Presented in this study are crystalline structure and mechanical properties of FePt(0.75)Pd(0.25) ternary alloy thin films deposited under the various annealing temperatures, obtained by means of transmission electron microscopy (TEM) and nanoindentation techniques. FePtPd ternary alloy thin films are deposited on Si substrates using a multi-target DC magnetron sputtering system. Results indicate that the grain size increase from 40 to 135 nm as the annealing temperature increases from 400 to 600 degrees C. From nanoindentation measurements, the hardness of FePtPd ternary alloy thin films are 11.6 +/- 0.4, 10.4 +/- 0.1 and 8.8 +/- 0.3 GPa for the annealed temperatures of 400, 500 and 600 degrees C, respectively. And, the corresponding Young's moduli are 175.4, 152.2 and 142.6 GPa, respectively. Hardness for FePtPd ternary alloy thin films decreased slightly in accordance with the increase of the grain size. By fitting experimental results with the Hall-Petch equation, a probable lattice friction stress of 5.15 +/- 0.05 GPa and Hall-Petch constant of 44.25 +/- 2.55 GPa nm(1/2) are obtained. (C) 2009 Elsevier B.V. All rights reserved.