Exchange interactions at surfaces of Fe, Co, and Gd

Abstract

Magnetic exchange interactions at low-index surfaces of bcc iron, hcp cobalt, and hcp gadolinium axe studied using ab initio electronic structure calculations. Interlayer exchange couplings derived from total-energy differences are enhanced at the surfaces over their bulk counterparts. This trend is in contrast to a surface reduction of on-site exchange parameters formulated within a classical Heisenberg model. A particular attention is paid to the sensitivity of exchange interactions at a Gd(0001) surface to relaxation of interlayer distances. The calculated results do not provide support for recently observed surface enhancement of the Curie temperature of the Gd metal.