Strain-induced distortion of the bulk bands of gadolinium

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Abstract
Thin films of gadolinium, approximately 8 ML thick, have been grown on the corrugated (112) surface of molybdenum and the electronic structure has been investigated with angle-resolved photoelectron spectroscopy. The unfavorable lattice match between the ‘‘steplike’’ Mo(112) substrate and the preferred hexagonally ordered Gd film results in an incommensurate Gd structure that appears to be ordered, but strained along the direction of the corrugations. The hexagonal Gd lattice is expanded by more than 20% along the ‘‘step’’ lines of the substrate, as determined from the reduced Brillouin-zone size along the ΓΣM high-symmetry line and low-energy electron diffraction. The induced strain substantially alters the conventional Gd 5d/6s bulk bands to exhibit a dispersion opposite to that of the relaxed Gd(0001) structure. Dislocations destroy the long-range crystallographic order in the direction orthogonal to the corrugations, which results in the localization of the bands along the ΓTK symmetry line. © 1996 The American Physical Society.