List of Figures

1. William Gilbert's magnetic model of the Earth
2. Coulomb's dipoles and Faraday's lines of force
3. An exploded view of the Hitachi Microdrive
4. Increasing storage density
5. A three-platter IDE hard disk drive, manufactured by Fujitsu in 1999
6. Energy density due to uniaxial anisotropy
7. Cubic anisotropy energy surfaces
8. The unit vectors of two moments $\ensuremath{\mathbf{S}}_i$ and $\ensuremath{\mathbf{S}}_j$
9. The functions $\cos{\phi}$ and $1-{\phi ^2 \over 2}$
10. The effect of altering the number of cells in a geometry
11. Finite difference and finite element meshes
12. Relaxed magnetisation from edge- and diagonally-aligned states
13. Typical hysteresis loops
14. Magnetic recording ideals
15. A typical ferromagnet
16. Domains formed in sample with closed flux
17. Micromagnetic system states
18. The simplified simulation process
19. OOMMF memory requirements
20. Memory usage scaling with magpar
21. Memory usage of OOMMF and magpar
22. A visualisation showing surface maps, streamlines, magnetisation and an isosurface
23. Massless particles highlighting core vortex
24. Out-of-plane and in-place vortices
25. Patterned and non-patterned media
26. Magnetoresistive random access memory
27. Single-domain and vortex states
28. Anisotropic simulation domain
29. Hysteresis loop for a flat nickel cylinder
30. Cylinder overview with magnetisation in a high applied field
31. Magnetisation in flat cylinder
32. Flower state and onion state in a cylinder
33. Flat cylinder entering the vortex state
34. Flat cylinder just before leaving the vortex state
35. Height dependence of state transition in cylinders
36. Phase diagram for nickel cylinders
37. Hysteresis loops for nickel spheres of diameter $d$=200nm
38. Nickel sphere in high applied field showing spin tapering
39. Sphere at high applied field
40. Sphere immediately after entering the vortex state
41. Sphere in vortex state
42. Sphere in late vortex state
43. Size dependence of nickel spheres
44. Hysteresis loops for nickel spheres of diameter 50nm and 80nm
45. Remanent magnetisation states in conical geometries
46. Phase diagram of remanent states in cones
47. Hysteresis loop for cone of $d=h=$100nm
48. Detailed points for cone reversal mechanism where $d=h=$100nm
49. Scanning electron microscope image of a droplet array
50. MOKE measurements for a nickel dot array
51. The double-template self-assembly technique
52. A typical nanodot ``droplet'' geometry
53. Hysteresis loop for a nickel half-sphere of diameter 200nm
54. Half-sphere at high applied field (point $a$ in figure 5.5)
55. Half-sphere in remanent vortex state
56. Half-sphere in late vortex state
57. Reversal mechanism phase diagram for part-spheres
58. Reversal mechanism for $d$=50nm, $h$=0.5$d$
59. Reversal mechanism for $d$=100nm, $h$=$d$
60. Hysteretic comparison of OOMMF (FD method) and magpar (hybrid FE/BE method)
61. Hysteresis loop for an isotropic nickel half-sphere of diameter 350nm
62. Two vortex states in an isotropic nickel half-sphere of diameter 350nm
63. Hysteresis loop for isotropic nickel half-sphere of diameter 750nm
64. Vortex ``pinning'' in three-quarter sphere
65. Reversal mechanism for nickel droplet of diameter 140nm
66. Hysteresis loops for droplets of bounding sphere diameter 140nm, 350nm and 500nm
67. Size dependence of coercive field in droplet nanodots
68. Comparison of experiment and simulation for nickel nanodots
69. Different hysteresis characteristics in droplet nanodots
70. Reversal mechanism of a droplet in a perpendicular applied field
71. Size dependence of out-of-plane coercive field in droplet nanodots
72. Size dependence of out-of-plane and in-plane coercivity in droplet nanodots
73. The single-template self-assembly technique
74. Scanning electron microscope image of an antidot array
75. Oscillation of coercivity observed experimentally
76. Cubically and hexagonally packed spheres
77. 600x600x150nm cut of simple cubic nickel antispheres
78. Magnetisation of a cobalt hexagonal antidot array in zero field
79. Hysteresis loop for permalloy antidot array
80. Microscopic images of an antidot array
81. Measured and computed demagnetising field of an antidot array in zero field
82. Measured and computed MFM signal of an antidot sample in a small applied field
83. Overview of Monte Carlo simulation
84. Coercivity of small permalloy nanodots
85. Coercivity of large permalloy nanodots
86. Monte Carlo simulation results
87. MOKE and numerical measurements for cobalt antidots
88. Polar plot of anisotropy energy and reversal conditions
89. The complete simulation process
90. The OOMMF Oxs framework
91. Simple constructive solid geometries