Micromagnetic behavior of conical ferromagnetic particles

Large area arrays of cobalt and nickel particles with truncated conical shapes and diameters of 80-120 nm have been prepared using interference lithography combined with an evaporation and lift-off process. The magnetic hysteresis has been measured and the remanent states of the particles have been compared with a three-dimensional micromagnetic model. The model shows a transition from "flower" to "vortex" magnetization states as the particle size increases. The distribution of switching fields and the magnetostatic interactions between particles have been characterized. Both lead to a slow approach to saturation in the hysteresis loops. The suitability of such arrays for data storage is discussed. (C) 2001 American Institute of Physics.