Ab initio study of electronic and magnetic properties of FeRh(001), FeRh(110) and FeRh(111) ultrathin films

Abstract

In this work, the structural, magnetic and energetic properties of ultrathin FeRh films grown in different crystallographic planes, namely (100), (110) and (111), are investigated by using density functional theory calculations. Different thicknesses, atom terminations and magnetic phases (FM and AFM) have been considered. The conclusions differ depending on the direction of growth. In general, values regarding surface energy follow the relationship σ110 < σ001 < σ111 where they grow with increasing thickness, the Rh-terminated surfaces also have higher values with respect to the Fe-terminated ones. Regarding stability, FeRh(001) and FeRh(110) surfaces have similar energy per atom values and are favoured with respect to FeRh(111). In relation to the study of the normal relaxations to surfaces from the thirteen systems, it could be concluded that except for the FeRh(111) surface where contractions between the layers are noticed regardless of termination and magnetic configuration, the other ones show relaxations. The importance of the magnetic order in the films energy stabilization is also analyzed. In summary, it could be said that in most cases Rh-terminated films present unstable and even unpredictable behaviors depending on the number of layers. This suggests that Rh is important in improving some properties, but only when the number of layers is less than that of Fe. That is, the film construction will depend on the specific interest of the particular application to be used in.