Microstructures and magnetism of different oxides separating FePt grains via ion-beam bombardment and annealing

Abstract

The effects of the fabrication methods and different capped oxide (SiO 2 and TiO 2) layers on the microstructure and magnetism of FePt thin films were studied. Both structural ordering (S ∼ 0:7) from the fcc FePt phase to the fct FePt phase and magnetic hardening were observed in the annealed FePt/SiO 2 thin films with a low substrate rotation speed (S r=1 rpm). However, only the annealed FePt/SiO 2 thin films prepared with a high S r (10 rpm) exhibited isolated FePt grains separated by the grain boundary SiO 2, as revealed by transmission electron microscopy and magnetometry. Furthermore, similar results in microstructures and magnetic properties were obtained after replacing the capped layer with TiO 2. However, an enhanced order parameter (S ∼ 0:85) and a smaller FePt grain size (∼6:8 nm), which are promising characteristics for ultrahighdensity magnetic recording, were achieved in the annealed FePt/TiO 2 thin films; however, the annealed FePt/SiO 2 thin films exhibited a larger grain size (∼15 nm). This indicates that TiO 2 inhibits the grain growth of FePt more effectively than SiO 2. © 2010 The Japan Society of Applied Physics.