Figure 1

Schematic diagram of the antidot geometry with the position of the square antidots marked with the letter A. The expected XMCD contrast is included for a magnetization sensitivity direction (MSD) along $y$. The antidot columns are parallel to $y$ and the rows are parallel to $x$. The easy and hard axes are along the $x$ and $y$ directions, respectively, and the field is applied parallel (or at a small angle) to $y$.Reuse & Permissions

Figure 2

Hysteresis loops obtained from longitudinal MOKE measurements, with the field applied parallel to $y$: (a) for a 10–nm-thick continuous film and (b)-(d) for antidot arrays $t=10\mathrm{nm}$ which show an increase in switching field as the antidot period, $p$, decreases. The initial small change in the magnetization corresponds to rotation of the magnetic spins in the antidot rows and the large change to the reversal of the antidot columns.Reuse & Permissions

Figure 3

XMCD images taken with PEEM of domain chains in $10\text{−}\mathrm{nm}$-thick antidot arrays with $p=$ (a) $1\mu \mathrm{m}$, (b) $400\mathrm{nm}$, and (c) $240\mathrm{nm}$.Reuse & Permissions

Figure 4

Magnetization reversal via domain chains observed with PEEM in a $10\text{−}\mathrm{nm}$-thick antidot array with $p=1\mu \mathrm{m}$. The array is first saturated with a positive field pulse $>195\mathrm{Oe}$, and the resulting remanent states are given after decreasing the field to zero (a) and applying increasing negative fields (b) to (i).Reuse & Permissions

Figure 5

Magnetization reversal in the antidot array in Fig. 4 ($t=10\mathrm{nm}$ and $p=1\mu \mathrm{m}$), with the magnetic field applied in the same direction as in Fig. 4 but this time with the magnetization sensitivity direction rotated by 90°. Here we observe a reversal of the rows perpendicular to the applied field direction via domain chains along $x$.Reuse & Permissions

Figure 6

(Color) Snapshots of a micromagnetic simulation of an antidot array with an area of $1.9\times 1.9\mu {\mathrm{m}}^2$, with antidot $\text{size}=\text{antidot}$ $\text{separation}=100\mathrm{nm}$, and a film thickness of $10\mathrm{nm}$. First, a positive field of $500\mathrm{Oe}$ was applied and then reduced to zero. The field was then increased in the negative sense in $50\mathrm{Oe}$ steps and remanent states captured after each increase in field. The applied field is at a small angle (5°) to the hard axis resulting in a reversal of the rows along $x$. The arrows at $H_A=+500\mathrm{Oe}$ indicate magnetic defects (magnetization sensitivity along $y$), which correspond to the ends of domain chains along $x$. The round frames at $H_A=-550\mathrm{Oe}$ indicate locations where the ends of orthogonal chains coincide and the oval frames at $H_A=-650\mathrm{Oe}$ indicate a row where several chain ends occur.Reuse & Permissions

Figure 7

(Color) XMCD images taken with PEEM of a $40\text{−}\mathrm{nm}$-thick antidot array with $p=800\mathrm{nm}$. (a) and (b) are the same array measured with orthogonal sensitivity directions, and (c) is the resulting two-dimensional color map determined from (a) and (b). The locations where the ends of orthogonal domains coincide are indicated with round frames.Reuse & Permissions

Figure 8

(Color) (a) Schematic diagrams of the different antidot configurations surrounding an antidot (A to D), at the antidot intersection (E to G) and at the end of a perpendicular domain chain (H and I). (b) Two-dimensional XMCD image taken with PEEM of an antidot array with $p=1\mu \mathrm{m}$ and $t=40\mathrm{nm}$, which includes contrast corresponding to the four basic configurations and a location where orthogonal chain ends coincide indicated by a round frame. (c) A color plot of a typical remanent state given by the micromagnetic simulations after application of a field of $-450\mathrm{Oe}$ (field parallel to $y$, initial applied field: $+1000\mathrm{Oe}$) with four 90° walls indicated by square frames and two 180° walls indicated by an oval frame.Reuse & Permissions

Figure 9

(Color online) Details of the micromagnetic simulation shown in Fig. 6. Starting with the remanent state after an applied field of $-450\mathrm{Oe}$, these are snapshots of the development of the magnetic spins on application of negative field of $-500\mathrm{Oe}$. Nucleation occurs by formation of diagonal domains (round frames), followed by propagation of the chain ends along the antidot array columns.Reuse & Permissions

Figure 10

(Color online) Details of a micromagnetic simulation similar to that shown in Fig. 6, but with the applied field parallel to $y$. Starting with the remanent state after an applied field of $-450\mathrm{Oe}$, (a) is the equilibrium state on application of a negative field of $-500\mathrm{Oe}$ and (b) is the remanent state after subsequent relaxation of the field to zero. The black arrowheads in (a) indicate locations where 360° walls form as the propagating chain ends approach a perpendicular chain, i.e., where there is a reversal of the magnetic spin direction in the rows. Several propagating chain ends approach a perpendicular chain forming a row of 360° walls indicated by the large arrow in (a). After relaxation of the field, they form a row of 90° walls indicated by the large arrow in (b). (c) XMCD image taken with PEEM of domain chains in a $10\text{−}\mathrm{nm}$-thick antidot array with $p=240\mathrm{nm}$. The array was first saturated with a negative field of $280\mathrm{Oe}$, and then the remanent states observed after application of increasing positive fields. This shows the remanent state after an applied field of $245\mathrm{Oe}$ and in contrast to Fig. 3c, the domain chains form in bands indicating the presence of perpendicular domain chains during reversal.Reuse & Permissions