Influence of dipolar interaction on small magnetic dot arrays

The effects of dipolar interaction in an array of small magnetic dots with perpendicular anisotropy are studied numerically within the framework of the Landau-Lifshitz-Gilbert equation. In the absence of a magnetic field, three typical configurations of the magnetic moments are found, depending on the dipolar coupling strength. Magnetization processes both parallel and perpendicular to the array are studied. The hysteresis loops are found to be highly sensitive to the dipolar coupling strength. The in-plane hysteresis loops are dominated by the strong dipolar interaction between particles, while the out-of-plane hysteresis loops are dominated by the perpendicular anisotropy. The coercive field, saturation field, and remanence are also sensitive to the strength of dipolar interaction. Dipole interactions also affect the characteristic switching time in a coupled array. Depending on the packing density of the dots in an array, the switching time may be shortened or lengthened. (c) 2005 American Institute of Physics.