Dependence of the magnetic energy barrier on the strength of the applied magnetic field in nanostructured cells of exchange-coupled trilayers

In this study, the change in the magnetic energy barrier is investigated as a function of the applied magnetic field. Elliptical nanostructured cells of exchange-coupled trilayers that have lateral dimensions of 160 nm (long axis) × 80 nm (short axis) are considered for various values of the thickness asymmetry for the two magnetic layers. An accurate analytical equation for the total energy, which includes effective magnetostatic fields averaged over the entire magnetic layer is used. In the absence of the thickness asymmetry, the magnetic energy barrier initially decreases slowly with increasing the magnetic field, followed by a steeper decrease in the intermediate field range. However, in the presence of thickness asymmetry, the decrease in the magnetic energy barrier occurs quite steeply even at small magnetic fields, and this tendency increases with increasing thickness asymmetry. Consequently, as the thickness asymmetry increases, the applied field dependence of the magnetic energy barrier approaches that observed for a single-layered thin film. A significant reduction of the magnetic energy barrier is observed by using the simplifying assumption concerning the magnetostatic fields which was frequently used in the past. This clearly emphasizes the importance of using an accurate equation for the total energy in calculating the magnetic energy barrier of nanostructured exchanged-coupled trilayers.