An Ising-model description of the L$1_0$ structure in fcc AB binary alloys with antiferromagnetic nearest-neighbor coupling (${\mathit{J}}_{\mathrm{nn}}$<0) and ferromagnetic next-nearest-neighbor interaction (${\mathit{J}}_{\mathrm{nnn}}$>0) leads to frustration in the bulk but a stable c(2×2) superstructure for a free (010) surface. Using Monte Carlo simulations with ${\mathit{J}}_{\mathrm{nnn}}$/${\mathit{J}}_{\mathrm{nn}}$=-0.05, we show that the surface orders at higher tmeperature than does the bulk. As the temperature is lowered towards the first-order bulk transition, surface-induced ordering occurs, thus producing the first confirmation of the prediction by Lipowsky.

• Received 23 July 1990

DOI:https://doi.org/10.1103/PhysRevLett.65.3321