Sputtering pressure effects on microstructure and grain orientation distribution in FePt thin films

We use the magnetron sputtering method to fabricate FePt thin films on amorphous oxidized Si substrates by controlling the sputtering pressure and investigate the evolution of microstructure and grain orientation using X-ray diffraction and electron back-scatter diffraction, and discuss the effect of microstructure on magnetic properties of L1₀-FePt thin film. The experimental results show that the L1₀-FePt phase is formed when the sputtering pressure is 0.25 Pa, and the L1₀-FePt phase is not found when the sputtering pressure is higher. The higher sputtering pressure leads to poor crystallinity and smaller grain size in FePt thin films, which inhibit disorder–order phase transformation. Meanwhile, higher sputtering pressure results in a larger residual strain, because it increases the degree of local gain misorientation in FePt thin films. The inverse pole figure map and band contrast map reveal the grain growth orientation and microstructure of L1₀-FePt thin film from cross-sectional, indicating that the grain grows along different direction, and exists in the form of nanocolumnar crystal. The experimental results demonstrate that when there is no texture in L1₀-FePt thin film, the out-of-plane magneto anisotropy of L1₀-FePt thin film should be mainly contributed by the shape anisotropy.