Analysis of the small-angle neutron scattering of nanocrystalline ferromagnets using a micromagnetics model - art. no. 214414

Citation
J. Weissmuller et al., Analysis of the small-angle neutron scattering of nanocrystalline ferromagnets using a micromagnetics model - art. no. 214414, PHYS REV B, 6321(21), 2001, pp. 4414
Citations number
61
Categorie Soggetti
Apllied Physucs/Condensed Matter/Materiales Science
Journal title
PHYSICAL REVIEW B
ISSN journal
01631829 → ACNP
Volume
6321
Issue
21
Year of publication
2001
Database
ISI
SICI code
0163-1829(20010601)6321:21<4414:AOTSNS>2.0.ZU;2-5
Abstract
In ferromagnets with a nonuniform magnetocrystalline and/or magnetoelastic anisotropy, such as nanocrystalline (nc-) or cold-worked (cw-) polycrystall ine materials, the static magnetic microstructure gives rise to strong elas tic magnetic small-angle neutron scattering (SANS). The paper explores a me thod for analyzing field-dependent SANS data from such materials in terms o f a model based on the theory of micromagnetics. Samples of cw Ni and of el ectrodeposited nc Ni and nc Co were characterized by x-ray scattering and m agnetometry, and were investigated by SANS both with and without polarizati on of the neutron beam. The variation of the differential scattering cross section with the scattering vector and with the applied magnetic held is we ll described by the model. Also, experimental results for the exchange stif fness constant A and for the spin-wave stiffness constant D obtained from t he analysis are found to agree with literature data obtained by inelastic n eutron scattering on single-crystal specimens, The model supplies an ''anis otropy field scattering function" that contains information on the magnitud e of the magnetic anisotropy in the material, and on the characteristic len gth scales on which the anisotropy changes direction. The results suggest t hat the anisotropy may be strongly nonuniform in each crystallite, possibly due to twinning, and that some magnetic moments in the Ni samples are stro ngly pinned at defects.