Abstract
This work has focused on the study of structure, morphology, and magnetic properties of the perpendicularly magnetized Fe/Pt epitaxial films on MgO (001) substrate by using the molecular beam epitaxy technique. We systematically controlled film morphology from isolated to continuous states with increasing film thickness to study the relationship between the morphology and magnetization reversal processes. The dominant magnetization reversal was found to change from Stoner-Wohlfarth rotation type to a domain-wall motion type as increasing film thickness. The Pt and Fe buffer layers were used to investigate the strain effect on the ordering of FePt films. The Pt buffer layer induces tensile strain that leads to lower ordering temperature of FePt films at 320 oC. Due to the full diffusion of Fe buffer layer into FePt films forming Fe-rich off-stoichiometric composition, the degree of chemical ordering is reduced. We first found that the insertion of symmetric Ag pinning layers (APL) into FePt films effectively enhances the coercivity much better than a single APL of the same total thickness. That is due to the relatively uniform-distributed defects than that of a single APL induced pinning effects to impede domain wall movement. A Cu layer on top of the FePt films not only promotes the chemical ordering but also reduces the intergranular exchange coupling to cause the coercivity enhancement. We aimed to reduce the grain size via introducing the MgO and SiO2 insert layers into Fe/Pt films for magnetic isolation. The methods successfully suppressed the grain growth of FePt films leading to decrease the coupling strength between grains.