Micromagnetic studies of three-dimensional pyramidal shell structures
A Knittel and M Franchin and T Fischbacher and F Nasirpouri and S J Bending and H Fangohr,
Micromagnetic studies of three-dimensional pyramidal shell structures,
New Journal of Physics 12, 113048 (23 pages) (2010)
Online: journal pdf (free), local postprint pdf
Motivation
- Most micromagnetic modelling is focussed on flat (essentially 2d) geometries.
- Recent interest through new growth techniques in truely 3d structures, in particular faceted core-shell structures with a non-magnetic core and a soft ferro-magnetic shell.
Summary
- systematic numerical analysis of the magnetic properties of pyramidal-shaped core-shell structures in a size range below 400nm.
- use standard micromagnetic model without the magnetocrystalline anisotropy term (Nmag software)
- vary the thickness of the shell between the limiting cases of an ultra-thin shell and a conventional pyramid and delineate different stable magnetic configurations.
- find different kinds of single-domain states (onion, flower, C and S states), and two types of vortex states in larger systems (symmetric and asymmetric vortex states)
- derive a phase diagram that specifies the magnetic ground state as a function of size and shell thickness.
- investigate metastability by investigating the stability of all occurring configurations for different shell thicknesses.
- compute hysteresis for selected sytems
- observe that the magnetic behaviour changes distinctively in the limit of ultra-thin shells
