Open AccessGrain‐size dependence of two‐dimensional micromagnetic structures for pseudo‐single‐domain magnetite (0.2–2.5 μm)
Author(s) -
Fukuma* Koji,
Dunlop David J.
Publication year - 1998
Publication title -
geophysical journal international
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.302
H-Index - 168
eISSN - 1365-246X
pISSN - 0956-540X
DOI - 10.1046/j.1365-246x.1998.00620.x
Subject(s) - micromagnetics , remanence , monte carlo method , condensed matter physics , single domain , magnetite , materials science , grain size , vortex , magnetization , physics , magnetic domain , mathematics , magnetic field , thermodynamics , statistics , composite material , quantum mechanics , metallurgy
Micromagnetic modelling with a Monte Carlo method was performed to obtain 2‐D micromagnetic structures of pseudo‐single‐domain (PSD) magnetite (0.2–2.5 μm). Cubic model grains were subdivided into a 2‐D array with a maximum of 100×100 cells. In order to find an appropriate cell size, the variation of the self‐consistency parameter ( S ) with cell size was examined. We regard solutions with S >0.95, which corresponds to cell sizes ≤0.03 μm, as representing realistic micromagnetic structures. For saturation remanence states, we found vortex structures for small PSD grains (≤0.25 μm) and closure domain structures for larger PSD grains (0.6–2.5 μm). Between 0.25 and 0.6 μm, structures remained chaotic even after a very large number of Monte Carlo steps. In grains with a closure domain structure, domain walls were usually subdivided into several segments with opposite polarities of magnetization rotation.