SEQUENTIAL TEMPERATURE-INDUCED PHASE TRANSITIONS FOR DYNAMIC DOMAIN EXPANSION IN EXCHANGE-COUPLED MULTILAYERS

Abstract

The evolution of the magnetization distribution with the temperature is investigated in a wide range (0-500K) in bilayers F1/F2 corresponding to a TbFeCo or DyFeCo layer F1 with perpendicular anisotropy exchange-coupled with a planar layer (F2) with low (GdFe and GdFeCo) or large (GdCo) in-plane anisotropy. The temperature dependences of the magnetic parameters (magnetization, uniaxial anisotropy, exchange constant) are first determined in the layers F1 and F2 from the mean field theory. In a second step the evolutions with the temperature of the magnetization distributions are obtained from a micromagnetic model using a non-continuous model of the magnetization. A re-orientation of the magnetization from in-plane to normal to the film F2 is stimulated at a switching temperature TS2 which depends strongly on the magnetic parameters (magnetization, effective anisotropy) of the planar layer. The extension of the analysis from ECDL (F1/F2) to ECTL (F1/F2/F3) with two in-plane magnetic layers F2 and F3 shows the possibility to induce sequential phase transitions at different switching temperatures TS2 and TS3 with a dynamic expansion of the transition in the capping layer F3 when TS3>TS2.