Crystallinity and its influence on physical and magnetic properties in phase change magnetic materials

Films of crystalline and amorphous Fe 12 (Ge 2 Sb 2 Te 5 ) 88 were prepared using laser synthesis from a stoichiometric target. The crystalline film, prepared at 300 °C was found to be in the hexagonal close packed (HCP) structure while the film prepared at room temperature was found to be amorphous. The crystalline film showed clear magnetic hysteresis, while the amorphous and the 220 °C prepared film exhibited weaker magnetic properties. The crystallization temperature of the amorphous Fe 12 (Ge 2 Sb 2 Te 5 ) 88 as extracted from resistance temperature measurements was found to be 168 °C, comparable to 178 °C for pure Ge 2 Sb 2 Te 5 . Lastly, the reflectivity spectrum showed the typical reflectivity contrast between crystalline or amorphous Fe 12 (Ge 2 Sb 2 Te 5 ) 88 films — as expected from phase change films.