Calculation of the magnetic energy barrier in nanostructured cells of synthetic ferrimagnets

A method is proposed to calculate the magnetic energy barrier of nanostructured cells of synthetic ferrimagnets. An important feature of the method is the use of an equation for the total energy that contains the magnetostatic fields at the saddle point as parameters of the energy equation. With no suitable methods of accessing the magnetic configuration at the unstable saddle point, it is difficult to obtain the saddle point magnetostatic fields. This difficulty is overcome with the use of equations that link the magnetostatic fields at the saddle point and critical fields, which are readily obtained by micromagnetic simulation. The present method is essentially based on the micromagnetic simulation, and, therefore, it should provide accurate results for the magnetic energy barrier. A contour diagram showing the thermal stability parameter is constructed as a function of the cell geometry and the thickness asymmetry, and the result should be of great value in designing magnetic cells for high density magnetic random access memory.