Regensburg 2010 – wissenschaftliches Programm
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MA: Fachverband Magnetismus
MA 9: Magnetic Particles, Clusters
MA 9.11: Vortrag
Montag, 22. März 2010, 18:00–18:15, H23
Magnetism of small Cr clusters: Structure, magnetic order and electron correlation effects — •Pedro Ruiz Díaz, Jose Luis Ricardo Chávez, Jesús Dorantes Dávila, and Gustavo Pastor — Institut für Theoretische Physik, Universität Kassel, Heinrich Plett Str. 40, 34132 Kassel, Germany
The magnetic properties of small CrN clusters (N ≤ 6) are investigated in the framework of density-functional theory (DFT). The interplay between electron correlations, cluster structure and magnetic order is quantified by performing fully non-collinear spin-unrestricted calculations. Results obtained using the spin-polarized local density approximation (LDA) and the generalized-gradient approximation (GGA) are contrasted. A dimer-based growth pattern is found in all considered low-lying isomers, with very short equilibrium bond lengths (typically deqGGA=1.55-1.65 Å) alternating with relative long ones (typically deqGGA=2.75-2.85 Å). Strong local magnetic moments µi→ are obtained for the relaxed geometries which show a collinear magnetic order with antiparallel (parallel) alignment of the µi→ along the short (long) bonds. Despite quantitative differences, both LDA and GGA functionals yield collinear ground-state solutions for the fully relaxed structures, non-collinear spin arrangements are found only for particular highly symmetric (non dimerized) geometries. The present work demostrates that the magnetic frustration in compact Cr clusters, is solved by dimerization rather than by non-collinearity of the local moments. Finally, implications of the present trends for the ground-state structure and magnetism of larger CrN clusters are discussed.