A lower bound for the volume-averaged mean-square magnetostatic stray field
Institut für Nanotechnologie, Forschungszentrum Karlsruhe, Karlsruhe, Germany
2 Technische Physik, Universität des Saarlandes, Saarbrücken, Germany
Corresponding author: a email@example.com
Published online: 31 October 2002
Based on a micromagnetics model, we develop a method through which quantitative information on the volume-averaged mean-square magnetostatic stray field due to non-zero divergences of the magnetization within the bulk of a ferromagnetic body can be obtained by analysis of magnetic-field-dependent small-angle neutron scattering data. In the limit of high applied magnetic field , when the direction of deviates only sligthly from , we have estimated a lower bound for as a function of the external field, and we have applied the method to bulk samples of nanocrystalline electrodeposited Ni and Co and coarse-grained polycrystalline cold-worked Ni. The root-mean-square magnetostatic stray field, which is inherent to a particular magnetic microstructure, shows a pronounced field dependence, with values ranging from about 5 to . Even at applied fields as large as , the quantity of nanocrystalline Co is still , which suggests that contributions to the total magnetostatic field originating from the bulk are significant in nanocrystalline ferromagnets; therefore, cannot be ignored in the interpretation of e.g. measurements of magnetization or spin-wave resonance. A comparison of with the volume-averaged mean-square anisotropy field reveals that both quantities are of comparable magnitude.
PACS: 61.12.Ex – Neutron scattering techniques (including small-angle scattering) / 75.30.Gw – Magnetic anisotropy / 75.50.Tt – Fine-particle systems; nanocrystalline materials / 75.75+a – Magnetic properties of nanostructures / 81.07.-b – Nanoscale materials and structures: fabrication and characterization
© EDP Sciences, Società Italiana di Fisica, Springer-Verlag, 2002