Growth of FexNi1-x ultrathin films on Cu(100) near the invar concentration

We have grown ultrathin FexNi1-x films epitaxially on Cu(100) with different stoichiometry. Previous measurements showed a deviation of the thickness dependence of T-c for a Fe75Ni25 alloy, which was not observed for smaller Fe concentrations. Therefore, we investigated the growth near this invar concentration more closely. With a charge coupled device camera based acquisition system, we observed the evolution of the reflection high-energy electron diffraction pattern during growth near the invar concentration. This allows us to determine the in-plane lattice constant of the top layer. Up to 66% Fe content, we see in-plane lattice constant oscillations similar to the Co/Cu(100) system [Fassbender et al., Phys. Rev. Lett. 75, 4476 (1995)]. At 80% Fe content, these oscillations are suppressed and we observe also a lattice contraction as expected from recent calculations. We discuss these results in connection with our previous results on the magnetic properties of FexNi1-x ultrathin films. (C) 1997 American Institute of Physics.