Simulation of the micromagnetic properties of sub-micron permalloy dot arrays

This paper examines the static micromagnetic properties of several configurations of sub-micron permalloy circular dots. Brief details of the two-dimensional (2-D) finite-element model used for the simulations are presented. The model is then applied to a 2×2 array of dots, showing that there is a single ground state in which the four dots assume an overall circular magnetisation distribution. It is then shown that introducing an additional central dot to the 2×2 array of dots yields a system with two ground states. Physical explanations for these states are given, and a phase diagram presented which shows the combinations of array parameters (dot diameter and separation) required for the system to adopt these two states. The final system examined combines two of the five dot arrays above side by side, and it is shown that this system has two ground states, one the inverse of the other. Potential applications for magnetic data processing of these arrays are discussed.