Micromagnetic structures of nanocrystalline ferromagnetic materials – comparison of simulation and experiment

Abstract

AbstractThe micromagnetic structure of nanocrystalline ferromagnetic materials is characterized by local fluctuations induced by the randomly varying magnetocrystalline anisotropy of the individual grains. Micromagnetic simulations may improve the understanding of the relevant features and the interpretation of the experimental observations of the magnetic structure. In this study we investigate the magnetic structure of nanocrystalline FeSi and Co model systems with average grain sizes of 20 nm to 60 nm. Small angle neutron scattering (SANS) is a suitable technique to study the micromagnetic structures of nanocrystalline materials at the nanometer scale. The simulated SANS curves for the FeSi model systems are compared with the experimental SANS curves of Vitroperm samples. It is found that the scattering at high fields is dominated by the local anisotropy fluctuations which can be well reproduced by the simulations. The simulations of the nanocrystalline hcp Co show that the stray fields resulting from the local magnetic fluctuations should lead to an observable contrast in magnetic force microscopy (MFM) images. We show that the contrast observed in the real MFM images of thin nanocrystalline hcp Co films compares well with the simulated image contrast with respect to magnitude and length scale of the observed fluctuations. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)