Effect of RuAl and TiN Underlayers on Grain Morphology, Ordering, and Magnetic Properties of FePt-SiO $_{\rm x}$ Thin Films

The impact of RuAl underlayers and TiN intermediate layers on the microstructure, L1_o ordering, and coercivity of granular FePt thin films is evaluated with an emphasis on controlling the FePt grains by using a new underlayer system. The use of the single RuAl/TiN film stacks does not help induce the epitaxial grain pick-up for FePt media due to their overly small grain size and smooth surface morphology. Two-step-deposited RuAl layers are developed to make a more open microstructure. By sputtering the top RuAl layers at low power and high Ar pressure, it is shown that there is a one-to-one grain matching between RuAl/TiN and FePt. It is also found that TiN underlayers are more favorable to the L1_o ordering process compared to MgO underlayers.