Ultrathin films of Mn on V{001}: gamma- or delta-Mn?

Ultrathin films of Mn grow pseudomorphically on V{001} up to thicknesses of about 15 Angstrom. A quantitative low-energy electron analysis finds the s tructure of the films to be body-centered tetragonal with a = 3.023 Angstro m (forced by the V{001} substrate) and c = 2.92+/-0.06 Angstrom, with a sli ghtly expanded first-interlayer spacing. Strain analysis (necessary in orde r to find the equilibrium phase of the films) requires knowledge of the cry stallographic and elastic properties of the possible equilibrium phases, wh ich are known only approximately and with large uncertainties, particularly for (bcc) delta-Mn. The available crystallographic data do not allow a con fident choice between gamma-Mn and delta-Mn as the equilibrium phase of Mn films grown on V{001} (this work) or on Pd{001} or Fe{001} as reported else where. [S0163-1829(99)05519-8].