Using Monte Carlo techniques, the surface critical behavior of three-dimensional semi-infinite axial next-nearest-neighbor Ising (ANNNI) models, with different surface orientations with respect to the axis of competing interactions, is investigated. Special attention is paid to the surface criticality at the bulk uniaxial Lifshitz point encountered in this model. The presented Monte Carlo results show that the mean-field description of semi-infinite ANNNI models is qualitatively correct… CONTINUE READING