8 research outputs found
Anisotropy of exchange stiffness and its effect on the properties of magnets
Using the spin-spiral formulation of the tight-binding linear muffin-tin
orbital method, the principal components of the exchange stiffness tensor are
calculated for typical hard magnets including tetragonal CoPt-type and
hexagonal YCo5 alloys. The exchange stiffness is strongly anisotropic in all
studied alloys. This anisotropy makes the domain wall surface tension
anisotropic. Competition between this anisotropic surface tension and
magnetostatic energy controls the formation and dynamics of nanoscale domain
structures in hard magnets. Anisotropic domain wall bending is described in
detail from the general point of view and with application to cellular Sm-Co
magnets. It is shown that the repulsive cell-boundary pinning mechanism in
these magnets is feasible only due to the anisotropic exchange stiffness if
suitably oriented initial pinning centers are available. In polytwinned
CoPt-type magnets the exchange stiffness anisotropy controls the orientation of
macrodomain wall segments. These segments may reorient both statically during
microstructural coarsening and dynamically during the macrodomain wall
splitting in external field. Reorientation of segments may facilitate their
pinning at antiphase boundaries.Comment: 9 pages, 2 figures, revtex4; to be published in J. Magn. Magn Mate
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With 13 refs., 42 tabs., 8 figs.SIGLETIB Hannover: RN 8908(89-118) / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekDEGerman