Nucleation and Annihilation of Magnetic Vortices in Sub-Micron Permalloy Dots
Understanding the magnetization reversal behavior in small dots have become one of the main focus area in the nanomagnetism recently. It is a subject of great scientific interest as well as technological importance. When the particles size is not too small (larger than the exchange length), the spins in such particles exhibit a vortex state without external magnetic field. When an external field is applied, the spins in these magnetic dots starts to align with the field. The dynamic process of the spin alignment occurs through annihilation of vortex. When the field is decreased, the vortex state reoccurs through nucleation. Novosad et al. have been using magnetic force microscopy to study the size dependence of the critical nucleation and annihilation fields. The static and dynamics of magnetization reverals in magnetostatically coupled dots are also a focus of this research.
V. Novosad, et al., IEEE Trans Magn, 37, 2088 (2001)