Two-dimensional Ising transition of epitaxial Fe films grown on Ag(100)

Fe(100) films and wedges between 2 and 4 monolayers thick were grown onto a Ag(100) single-crystal substrate. High- and low-energy electron-diffraction observations confirm the epitaxy. The magnetic phase transition near the Curie temperature ${\mathit{T}}_{\mathit{C}}$ was investigated in situ by means of the surface magneto-optic Kerr effect. The temperature dependence of the magnetization follows a universal power law of M(T)∝(1-T/${\mathit{T}}_{\mathit{C}}$ ${)}_{\mathit{c}}^{\mathrm{\beta }}$ with an effective value of ${\mathrm{\beta }}_{\mathit{c}}$≊1/8(0.124±0.002), which indicates that the phase transition is two-dimensional Ising class. This and the observed perpendicular easy axes are attributed to the surface magnetic anisotropy.