Laser-induced magnetization precession parameters dependence on Pt spacer layer thickness in mixed magnetic anisotropies Co/Pt/Co trilayer

Laser-induced magnetization dynamics was investigated in Co/Pt/Co trilayer, with 1 nm thick Co-sublayers, as a function of Pt-spacer layer thickness ( d Pt ) using time-resolved magneto-optical Kerr effect. The magnetization precession parameters: frequency (f), amplitude (A) and effective damping parameter ( α eff ) dependencies on the external magnetic field (H) were determined as a function of d Pt . Three different regions of Pt layer thickness: 0–1.3 nm, 1.3–2.5 nm, and 2.5–4 nm, denoted as regions I, II, and III, respectively, exhibiting distinctly different magnetic properties, were distinguished. It is found that as d Pt increases reorientation of Co-magnetizations from in-plane to perpendicular direction occurs at d Pt around 1.2 nm. For d Pt > 2.5 nm magnetization reorientation from parallel to the orthogonal directions due to mixed anisotropies in Co-layers appears. It is found that in the whole d Pt range single magnetization precession frequency occurs, despite different effective magnetic anisotropies of Co-sublayers. Simulation of the magnetization precession parameters was performed in an effective magnetic layer model. We found that the observed A ( H ) behavior is well simulated within the model in region I and III. The α eff ( H ) correlations with A ( H ) in different d Pt regions are discussed.