Three-dimensional magnetization reversal measurements in nanoparticles

The first three-dimensional switching field measurements of an individual nanometer-sized magnetic particle are presented. The angular dependence of the switching held can be described by the model of uniform rotation of magnetization. However, the anisotropy function proposed by Stoner and Wohlfarth appears to be simplistic. In order to reproduce the measured switching fields, one has to take into account higher order anisotropy terms. These terms are very important to understand dynamical magnetization reversal properties in the classical and the quantum regimes.