Surface Critical Behavior of Binary Alloys and Antiferromagnets: Dependence of the Universality Class on Surface Orientation

TL;DR

This paper investigates how the surface orientation affects the critical behavior of binary alloys and antiferromagnets, revealing that universality classes depend on surface orientation, unlike in ferromagnets.

Contribution

It demonstrates that surface universality classes in antiferromagnets and alloys depend on surface orientation, contrasting with ferromagnetic systems, supported by transfer-matrix calculations and other evidence.

Findings

Surface universality class depends on surface orientation.

Ordinary and extraordinary critical behaviors are distinguished.

Transfer-matrix calculations confirm the orientation dependence.

Abstract

The surface critical behavior of semi-infinite (a) binary alloys with a continuous order-disorder transition and (b) Ising antiferromagnets in the presence of a magnetic field is considered. In contrast to ferromagnets, the surface universality class of these systems depends on the orientation of the surface with respect to the crystal axes. There is ordinary and extraordinary surface critical behavior for orientations that preserve and break the two-sublattice symmetry, respectively. This is confirmed by transfer-matrix calculations for the two-dimensional antiferromagnet and other evidence.