Regensburg 2010 – wissenschaftliches Programm

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MA: Fachverband Magnetismus

MA 9: Magnetic Particles, Clusters

MA 9.12: Vortrag

Montag, 22. März 2010, 18:15–18:30, H23

Magnetism, structure and chemical order in small FeRh clusters — •Junais Mokkath and Gustavo Pastor — Institut für Theoretische Physik, Universität Kassel, Heinrich Plett Straße 40, 34132 Kassel, Germany.

The structural, electronic and magnetic properties of small Fe_m Rh_n clusters having N = m+n ≤ 8 atoms are investigated in the framework of a generalized gradient approximation to density-functional theory. 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 a different topology than the optimal structure, while for larger clusters the lowest-energy isomerizations imply mainly changes in the chemical order. The correlation between structure, chemical order, and magnetic behavior is analyzed as a function of size and composition. For all clusters having the optimized most stable structure the magnetic order is found to be Ferromagnetic-like, Antiferromagnetic-like spin arrangements were found in some low-lying isomers. The average magnetic moment per atom µ_N increases approximately linearly with Fe content. A remarkable enhancement of the local Fe moments is observed as result of Rh doping. This is a consequence of the increase in the number of Fe d holes, due to FeRh charge transfer, combined with the extremely reduced local coordination. The Rh local moments, which are important already in the pure clusters (N≤ 8) are not significantly enhanced by Fe doping. However, the overall stability of magnetism– as measured by the total energy gain upon spin polarization at T=0– increases when Rh is replaced by Fe.