Interplay between Chemical and Magnetic Order in FeRh Clusters

Abstract

The structure, chemical order, and magnetic behavior in small FeRh clusters having N ≤ 19 atoms have been investigated theoretically. For N ≤ 6 atoms, a thorough global geometry optimization is performed by considering all possible cluster topologies, while for 7 ≤ N ≤ 19 only a few representative structures are considered. In all cases, the starting structures are fully relaxed in the entire range of concentrations and spin polarizations. The calculations are based on a generalized-gradient approximation to density-functional theory. The results are analyzed systematically as a function of size and composition. The optimized cluster structures are compact with a clear tendency to maximize the number of nearest-neighbor FeRh pairs. For very small sizes, the low-lying isomers present usually a topology different from that of the optimal structure, while for larger clusters the lowest-energy isomerizations imply mainly changes in the chemical order. The most stable structures are in general ferromagnetic. A...