Microstructural evolution and phase transformation characteristics of Zr-doped FePt films

In the present study, an emphasis was given on elucidating the details of microstructural changes in both undoped FePt and Zr-doped FePt films upon exposure to postdeposition annealing. Recently, the present authors have discovered [S. R. Lee, S. Yang, Y. K. Kim, and J. G. Na, Appl. Phys. Lett. 78, 4001 (2001)] that 3 at. % Zr doping into Fe59Pt41 films accelerated the ordering kinetics (10 min at 500 degreesC), accompanying high coercivity H-c of 7.3 kOe. Our transmission electron microscopy study on both Fe59Pt41 and [Fe59Pt41](97)Zr-3 films annealed at 500 degreesC for 60 and 10 min, respectively (both exhibited H-c=7300 Oe) revealed that the FePtZr film displayed excellent microstructural features: smaller average grain size (D) with narrower distribution (sigma) (D=6.0 nm,sigma=2.3 nm) compared with FePt (D=33.6 nm, sigma=25.0 nm). For the FePtZr system, we have found that an ordered phase decomposed into disordered phases (thereby losing the high H-c) after 15 min annealing. By evaluating the long-range-order parameter S changes, we speculate that the cause of the disordering was primarily due to the formation of a Pt-Zr compound. (C) 2002 American Institute of Physics.