8 Magnetic Self-Assembling of Spherical Co Nanoparticles …
209
A
B
C
Fig. 8.17 Snapshots of configurations for a confined Stockmayer fluid at μ = 2.0, ρ = 0.2, T =
1.25, and H = 20. a L = 10, b L = 27, c L = 4
created by the pattern. This approach has been widely applied [99–102] and leads
to the following general results: the pattern size such as the radius of columns and
the width of labyrinth decreases with the magnetic field strength to reach saturation
at high field strength. The ratio of the pattern size and height decreases with the
height. A transition between different kinds of patterns is not induced by a change
in pattern height or field strength. These transitions are mainly determined by the
volume fraction defined as the ratio of the volume occupied by the magnetic phase
to the total volume of the film. The self-organization of MNPs in a perpendicular
field has also been studied by Monte Carlo simulations using a confined Stockmeyer
fluid in the gas–liquid coexistence [7, 103]. System parameters have been chosen
close to cobalt NPs coated with dodecanoic acid. The decrease of the pattern size
with field strength is in good agreement with the results from free energy approaches