Ge0.7Mn0.3 thin films were fabricated on Al2O3 (0001) and glass substrates at growth temperatures ranging from room temperature to 500 degrees C by a radio frequency magnetron sputtering. We found that the Ge0.7Mn0.3 thin films showed a polycrystalline-to-amorphous transition at about 360 degrees C, and the ferromagnetic transition temperature of each thin film depends on its structure crystalline or amorphous states. Particularly, the Ge0.7Mn0.3 thin films showed room temperature ferromagnetism when they were fabricated at temperatures above the crystallization temperature. (C) 2009 Elsevier B.V. All rights reserved.