Breakdown of the bi-dimensional symmetry in bct Fe layers by epitaxy on Co(1 1 (2)over-bar-0) surface

The structure of thin Fe overlayers on the Co(1 1 2 0) surface has been inv estigated by low energy electron diffraction (LEED) and by primary-beam dif fraction modulated electron emission (PDMEE), as a function of the Fe cover age (6-50 ML) and of the substrate temperature (between room temperature an d 300 degreesC). The structure of the layers was the tetragonally distorted bet modification of the equilibrium bcc phase with the (0 0 1)Fe//(1 1 2 0 )Co and [1 1 0]Fe//[1 1 0 0]Co relationships with the Co substrate. The Fe( 0 0 1)-Co(1 1 2 0) system exhibits a very large misfit asymmetry in the int erface plane. As a consequence, a breakdown of the long-range order occurs in the Fe film along the [1 1 0 0] substrate direction. (C) 2001 Elsevier S cience B.V. All rights reserved.