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Micromagnetic modeling of Bloch Walls with Néel Caps in Magnetite
Author(s) -
Xu Song,
Dunlop David J.
Publication year - 1996
Publication title -
geophysical research letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.007
H-Index - 273
eISSN - 1944-8007
pISSN - 0094-8276
DOI - 10.1029/96gl01568
Subject(s) - magnetite , domain wall (magnetism) , spins , condensed matter physics , demagnetizing field , magnetic force microscope , micromagnetics , materials science , magnetic domain , physics , magnetic field , magnetization , quantum mechanics , metallurgy
Two‐dimensional micromagnetic modeling of 180° domain walls in magnetite predicts that at depths >0.07 micro;m below the surface, the walls are Bloch‐like, with spins rotating in the plane of the wall in order to eliminate magnetic poles on the wall and reduce demagnetizing energy, E d . The Bloch wall width is ≈ 0.16 µm, in agreement with magnetic force microscope (MFM) data. Near a crystal boundary, the walls are Néel‐like: spins rotate in the plane of the surface in order to eliminate surface poles. This Néel cap is ≈ 0.3 µm wide and is offset with respect to the underlying Bloch wall. The Néel cap is narrower and shallower in magnetite (relative to Bloch wall width) than in iron, mainly because E d is not as overwhelmingly important compared to other energies in magnetite as it is in iron. As a consequence of the smaller Néel cap in magnetite, the surface field produced by a domain wall is due mainly to the underlying Bloch wall, with only a minor contribution from the Néel cap. This prediction is consistent with MFM imaging of domain walls on free surfaces of magnetite crystals.