Ferromagnetic resonance line width in Co(x)-SiO2(1-x) granular films

摘要

Using ferromagnetic resonance at X-band (v = 9.4 GHz) and Q-band (v = 34 GHz) we have studied the magnetic behavior of heterogeneous CO-SiO2 granular films as a function of the Co volume concentration, x, and the temperature, T. We have observed a main absorption signal associated to the uniform precession of the magnetic moments in the entire x-range studied. We have also observed an additional absorption above a critical concentration (x(c) = 0.37) that could be associated to a surface resonance mode. We have found that annealing the films at moderate temperatures produce irreversible changes in the film microstructure. Based on the surface inhomogeneity model we propose that the two surfaces are affected in a different way during the annealing process. Measurements of the line width as a function of x and T could be explained within the framework of an array of randomly distributed anisotropic particles with increasing exchange interactions for larger x. (C) 2004 Elsevier B.V. All rights reserved.