Structure and magnetism of cobalt clusters

J. L. Rodríguez-López, F. Aguilera-Granja, K. Michaelian, and A. Vega
Phys. Rev. B 67, 174413 – Published 20 May 2003
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Abstract

The lowest-energy geometric structures and isomers of freestanding CoN clusters (4<~N<~60) and their corresponding magnetic moments are calculated using an evolutive algorithm based on a many-body Gupta potential and a self-consistent spd tight-binding method, respectively. We found an icosahedral growth pattern for the global minimum with some hcp and fcc structures for some particular sizes, whereas for the second isomer, distorted icosahedral structures are obtained in general. With the aim to study the possible coexistence of isomers within the experimental cluster beam we assumed an equilibrium distribution and calculated for each cluster size the different coexistent structures and the relative populations at room temperature. Our results show that the coexistence is present only at some particular sizes, in agreement with chemical-adsorption and photoionization experiments. Our self-consistent tight-binding calculations considering 3d, 4s, and 4p valence electrons for the magnetic properties show that the magnetic moments for the global minima and the second isomers are in general very similar except in a small region of 20<N<40 atoms where the magnetic moment of the global minimum is smaller than that of the second isomer. We compare our results for the magnetic behavior of the global minimum with theoretical calculations available in the literature as well as with experimental results.

  • Received 11 December 2002

DOI:https://doi.org/10.1103/PhysRevB.67.174413

©2003 American Physical Society

Authors & Affiliations

J. L. Rodríguez-López1,2, F. Aguilera-Granja3, K. Michaelian4, and A. Vega5

  • 1Instituto Potosino de Investigación Científica y Tecnológica, A. C., Apartado Postal 3-74 Tangamanga, 78231 San Luis Potosí S.L.P., Mexico
  • 2Texas Materials Institute, The University of Texas at Austin, Austin, Texas 78712-1063
  • 3Instituto de Física, Universidad Autónoma de San Luis Potosí, 78000 San Luis Potosí S.L.P., Mexico
  • 4Instituto de Física, Universidad Nacional Autónoma de México, 20-364, 01000 D.F., Mexico
  • 5Departamento de Física Teórica, Atómica, Molecular y Nuclear, Universidad de Valladolid, E-47011 Valladolid, Spain

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Vol. 67, Iss. 17 — 1 May 2003

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