Schematic diagram of magnetic caps on nanospheres, self-assembled on a silicon nitride membrane and the used measurement geometry in STXM.
Magnetization loops of a Fe/Gd multilayer, probed by polar MOKE. A reference film on a flat substrate exhibits a hard-axis hysteresis loop whereas rectangular-shaped easy-axis loops are observed on silica nanospheres with diameters of 800, 300, and 160 nm.
Calculated demagnetization energies of slab structures, circular disks, hemispheres, crescent-shaped nanocaps, and nanocaps with constant film thickness as a function of the system size. For all diameters above about 100 nm curved structures show lower values of than planar structures. The reason therefore, namely the reduction in the magnetic charges by the curved surface, is illustrated in the inset.
STXM images at various perpendicular magnetic fields. At intermediate field values domains of opposite magnetization nucleate and move around the rim and finally toward the center. At ±361 a saturated state can be observed.
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