The L12 CrPt3 underlayer effect on the ordering of L10 FePt films

This study discusses the effects of a CrPt3 alloy underlayer on the magnetic properties and microstructure of FePt films. The L12 CrPt3 phase was chemical long-range ordered at a temperature above 600 °C, and the 120-nm thick CrPt3 film annealed at 800 °C, resulting in ferrimagnetic behavior. The long-range ordered CrPt3 underlayer slightly increased the ordering of the L10 FePt film, as evidenced by the individual L12 CrPt3 and L10 FePt (0 0 1) superlattice peaks. An X-ray slow scan of the [FePt/CrPt3(T °C)]400°C bilayer shows that the integrated intensity of the L10 FePt (0 0 1) peaks was higher on the long-range order L12-type CrPt3 (T = 600, 800) underlayer and lower on the partial short-range order L12 and A1-types CrPt3 (T = 400) underlayer. However, optimal magnetic properties were obtained in the [FePt/CrPt3(400 °C)]400°C bilayer. When a FePt film is deposited on a ferrimagnetic CrPt3(800 °C) underlayer, the resulting bilayer shows isotropic magnetic hysteresis loops and cannot be saturated at 1.8 T. Atomic force microscopy (AFM) and transition electron microscopy (TEM) show that the L12 CrPt3(800 °C) underlayer exhibits coarse surface roughness and plate-like grains, respectively. From TEM images, all the FePt grains were isolated uniformly by CrPt3 matrix.