T-induced changes of magnetization profiles and reversal in exchange-coupled trilayers

Thermomagnetic phenomena are investigated in appropriate exchange-coupled trilayers at the basic of a magnetic amplification of the magnetically-induced super-resolution signal used for ultrahigh magneto-optical storage. The changes of the magnetization profiles and reversal behavior between room temperature and the Curie temperature are determined from the mean field theory and a micromagnetic model based on a discontinuous distribution of the magnetization and compared in bi- and trilayers F₁/F₃ and F₁/F₂/F₃. These multilayers correspond to a TbFeCo layer F₁ with perpendicular anisotropy exchange-coupled with either one GdFeCo (F₃) or with a double GdFe/ GdFeCo (F₂/F₃) in-plane magnetic layer. Depending on the magnetic parameters of the in-plane layers associated with appropriate choice of their composition, it is possible to stimulate sequential magnetic reorientation in the layers F₂ and F₃ at different switching temperatures T_s2 and T_s3 which can induce a dynamic expansion of the magnetic domains in the upper readout layer.