2001/08/20 by F. Luis, Fernando Luis, J. M. Torres +13 · 2 citations
Physics and Astronomy · #Advanced Condensed Matter Physics #Magnetic properties of thin films #Theoretical and Computational Physics #cond-mat.mtrl-sci
paper · pdf · doi:10.1103/physrevb.65.094409
13 figures submitted to Phys. Rev. B
arxiv created 2001/08/20 · openalex publication_date 2002/02/06 · arxiv updated 2009/11/30 · openalex created_date 2025/10/10 · openalex updated_date 2026/07/28
We study the magnetic properties of spherical Co clusters with diameters between 0.8 nm and 5.2 nm (25--7000 atoms) prepared by sequential sputtering of Co and Al2O3. The particle size distribution has been determined from the equilibrium susceptibility and magnetization data and it is compared with previous structural characterizations. The distribution of activation energies has been independently obtained from a scaling plot of the ac susceptibility. Combining these two distributions we have accurately determined the effective anisotropy constant Keff. We find that Keff is enhanced with respect to the bulk value and that it is dominated by a strong anisotropy induced at the surface of the clusters. Interactions between the magnetic moments of adjacent layers are shown to increase the effective activation energy barrier for the reversal of the magnetic moments. Finally, this reversal process is shown to proceed classically down to the lowest temperature investigated (1.8 K).