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

Thermomagnetic phenomena are investigated in appropriate exchange-coupled t rilayers at the basic of a magnetic amplification of the magnetically-induc ed super-resolution signal used for ultrahigh magneto-optical storage. The changes of the magnetization profiles and reversal behavior between room te mperature and the Curie temperature are determined from the mean field theo ry and a micromagnetic model based on a discontinuous distribution of the m agnetization and compared in bi- and trilayers F-1/F-3 and F-1/F-2/F-3. The se multilayers correspond to a TbFeCo layer F-1 with perpendicular anisotro py exchange-coupled with either one GdFeCo (F-3) or with a double GdFe/GdFe Co (F-2/F-3) in- plane magnetic layer. Depending on the magnetic parameters of the in-plane layers associated with appropriate choice of their composi tion, it is possible to stimulate sequential magnetic reorientation in the layers F-2 and F-3 at different switching temperatures T-s2 and T-s3 which can induce a dynamic expansion of the magnetic domains in the upper readout layer. (C) 1999 American Institute of Physics. [S0021-8979(99)33308-9].