Effect of annealing temperature on microstructure and magnetism of FePt/TaOx bilayer

The effect of annealing temperatures on the microstructures and magnetism of FePt/TaOx bilayers was systemically investigated in the range of 25–650 °C. Microstructural characterization reveals that higher annealing temperatures lead to higher ordering parameters and larger grain sizes. High order parameter up to 0.57 was acquired after the sample was annealed at 600 °C. Diffusion was observed from TaOx layer into FePt layer after annealing at temperature over 550 °C. The out-of-plane coercivity first increased and exhibited a maximum value up of 4.2 kOe after annealing at 550 °C and decreased as the annealing temperature was further increased. The coercivity increase with higher annealing temperature was attributed to the rise of magnetocrystalline anisotropy due to the formation of the ordered fct FePt structures.

The ion beam sputtered TaOx on FePt can be diffused into FePt after annealing. This diffusion is very sensative to the annealing temperature. 550 °C is the optimize temperature for annealing FePt with a highest out-of-plane coercivity.Figure optionsDownload as PowerPoint slideHighlights
► Ion beam sputtered TaOx on FePt.
► FePt with different annealing temperatures.
► Microstructures vary with annealing temperatures.
► Coercivity varies with annealing temperatures.
► FePt for magnetic recording media.