Thermal stability and critical switching field of nanostructured synthetic ferrimagnets.

In this study, the thermal stability and critical switching field of nanostructured elliptical synthetic ferrimagnets are calculated by using an analytical/numerical combined method, and the relationship between the two parameters is investigated. In conventional single magnetic layers, the critical switching field is a good measure of the thermal stability since the anisotropy, which determines the thermal stability, scales with the critical switching field. However, no such correlation is expected in nanostructured synthetic ferrimagnets, where the anisotropy is poorly defined owing to the strong interlayer magnetostatic interactions between two magnetic layers. This behavior is explained by the difference in the variation of the thermal stability with the external magnetic field as a function of the thickness asymmetry between two magnetic layers. The variation is found to be smaller at a smaller thickness asymmetry, where the interlayer magnetostatic coupling is stronger. This result indicates that the correlation between the two parameters is poorest in the completely symmetric synthetic ferrimagnet, but it increases with increasing thickness asymmetry of the synthetic ferrimagnets.