The occurence of modulated phases in thin films of ErAl3 and Er1−xGdxAl3

Abstract In this paper we report studies on the formation and crystal characterization of modulated phases in ErAl 3 and Er 1− x Gd x Al 3 ( x = 0.17 or 0.50) alloy thin films. The alloy films were investigated using electron microscope techniques. The asdeposited films were amorphous. On annealing they readily underwent an amorphous-to-crystalline transformation. The transformed single crystals corresponded to polytypically modulated phases. In ErAl 3 the observed phases were 3C, 4H and 6H. In Er 0.83 Gd 0.17 Al 3 , 3C, 4H, 6H, 15R and high period disordered phases were found to occur. In the case of Er 0.50 Gd 0.50 Al 3 , the observed phases corresponded to 3C, 4H, 6H, 9R, 12R, 15R, 16H, 24H and high period disordered phases. A possible mechanism for the formation of these phases, in terms of an interaction between the Fermi surface and the Brillouin zone leading to a lowering of the electron energy, is suggested.