Ferromagnetic resonance in arrays of highly anisotropic nanoparticles
Centro Atómico Bariloche, Comisión Nacional de Energía Atómica, and Instituto Balseiro, Universidad Nacional de Cuyo, 8400 San Carlos de Bariloche, Río Negro, Argentina
Corresponding author: a firstname.lastname@example.org
Revised: 26 June 2006
Published online: 31 July 2006
We present in this study computational simulations of the ferromagnetic resonance response of magnetic nanoparticles with a uniaxial anisotropy considerably larger than the microwave excitation frequency (in field units). The particles are assumed to be randomly oriented in a two dimensional lattice, and are coupled by dipolar interactions through an effective demagnetization field, which is proportional to the packing fraction. We have included in the model fluctuations in the anisotropy field (HK) and allowed variations in the demagnetizing field. We then analyzed the line shape and line intensity as a function of both fields. We have found that when HK is increased the line shape changes drastically, with a structure of two lines appearing at high fields. The line intensity has a maximum when HK equals the frequency gap and decreases considerably for larger values of the anisotropy. The effects of fluctuations in HK and variations in the packing fraction have been also studied. Comparison with experimental data shows that the overall observed behavior is dominated by the particles with lower anisotropy.
PACS: 76.50.+g – Ferromagnetic, antiferromagnetic, and ferrimagnetic resonances; spin-wave resonance / 75.30.Gw – Magnetic anisotropy / 75.50.Tt – Fine-particle systems; nanocrystalline materials / 75.75.+a – Magnetic properties of nanostructures
© EDP Sciences, Società Italiana di Fisica, Springer-Verlag, 2006