ROLE OF FILM ROUGHNESS AND INTERDIFFUSION IN THE FORMATION OF NONFERROMAGNETIC FCC FE IN THE FE CO(100) SYSTEM/

The fcc Fe/Cu(100) and Fe/Co(100) systems are characterized by a wide range of magnetic and structural phases. In particular, a nonferromagn etic fcc phase with a live layer has, been observed for room temperatu re growth Fe films in the similar to 5-11 ML thickness range. This non ferromagnetic phase is not present for low temperature (similar to 120 K) grown films even when the film temperature is raised to room tempe rature. Annealing the film at 475 K, however, will recover the room te mperature phase. Two effects that could account for these features are interdiffusion and surface smoothening. In order to determine which o f these effects is responsible for the occurrence of the nonferromagne tic phase, we performed experiments on the Fe/Co(100) system to separa te these two effects. An artificially roughened sample grown at room t emperature exhibits a ferromagnetic phase only. A sample grown at low temperature in which the first few layers are alloyed to simulate inte rdiffusion also shows the ferromagnetic phase. Experiments in which a few layers of varying thicknesses are grown at room temperature and th e rest of the film is grown at low temperature exhibit different magne tic phases depending on the thickness of the room temperature grown la yer. These results indicate that film roughness is the main factor tha t determines whether the nonferromagnetic phase of fcc Fe will be pres ent in the similar to 5-11 ML thickness range. (C) 1997 American Insti tute of Physics.