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

Abstract

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 (dPt) using time-resolved magneto-optical Kerr effect. The magnetization precession parameters: frequency (f), amplitude (A) and effective damping parameter (αeff) dependencies on the external magnetic field (H) were determined as a function of dPt. 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 dPt increases reorientation of Co-magnetizations from in-plane to perpendicular direction occurs at dPt around 1.2 nm. For dPt>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 dPt 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 αeff(H) correlations with A(H) in different dPt regions are discussed.