Micromagnetic Simulation of Dynamic and Thermal Effects

Abstract

Small magnetic elements are the basic structural units of magneto-electronic devices (Prinz, 1999) and discrete storage media (Terris et al., 1999). The development of magnetic sensors or magnetic memory cells requires a precise knowledge of the magnetization reversal mechanism of magnetic nanostructures. Finite element micromagnetics take into account the complex microstructure of magnetic materials such as edge roughness, grain structure and particle shape. In combination with magnetic imaging using magnetic force (Dahlberg and Zhu, 1995) and Lorentz (Kirk et al., 1997) microscopy, the simulations provide a useful tool to characterize the reversal magnetization reversal process. Both in magnetic recording and in magnetic memory cells as used in magnetic random access memories, a high data rate is desired. Numerical micromagnetics can provide a basic understanding of the switching dynamics. If the particles are sufficiently small, the magnetization reverses by quasi-uniform rotation (Street and Crew, 1999). Then the energy barrier for thermally activated switching decreases with decreasing particle volume. Thus with decreasing size of the structural magnetic units, thermal effects become important and may influence the switching time.