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 nonferromagnetic fcc phase with a live layer has been observed for room temperature growth Fe films in the ∼5–11 ML thickness range. This nonferromagnetic phase is not present for low temperature (∼120 K) grown films even when the film temperature is raised to room temperature. Annealing the film at 475 K, however, will recover the room temperature phase. Two effects that could account for these features are interdiffusion and surface smoothening. In order to determine which of these effects is responsible for the occurrence of the nonferromagnetic phase, we performed experiments on the Fe/Co(100) system to separate these two effects. An artificially roughened sample grown at room temperature exhibits a ferromagnetic phase only. A sample grown at low temperature in which the first few layers are alloyed to simulate interdiffusion also shows the ferromagnetic phase. Experiments in...