Ferromagnetic stabilization of ordered B2 $\mathrm{FeRh}$ thin films

The electronic structure and the local spin polarization of the (001) FeRh thin films have been studied within density-functional formalism. Bulk B2 FeRh is an ordered alloy, with in-plane antiferromagnetism (AF-II) in the Fe layers as ground state and a ferromagnetic configuration a few millirydberg above. A transition from antiferromagnetic to ferromagnetic configuration is obtained when the temperature is increased or when an excess of Fe is introduced. Here we demonstrate that a decrease of the film thickness leads to similar transition. For Rh-terminated FeRh (001) surfaces, the calculations show that the ground state of the film is ferromagnetic for nine layers whereas for 15 layers it is antiferromagnetic as in bulk FeRh.