The necessity for employing a low substrate temperature for MnAs growth in molecular beam epitaxy has been clarified through an investigation for the effect of the growth temperature on the microscopic structural morphology. The atomic registry of MnAs films on GaAs substrate was examined by transmission electron microscopy. The MnAs films revealed a single-crystalline nature at similar to300degreesC, but the morphology changed to polycrystalline with an increase in the substrate temperature. The variation in the degree of the magnetic anisotropy of the films was consistent with the change of the film morphology along with the substrate temperature. The umaxial in-plane magnetic anisotropy of the epitaxial MnAs film was correlated with the surface reconstruction on the GaAs substrate. (C) 2004 Elsevier B.V. All rights reserved.