Chemical diffusion in L10-ordered FePt

Abstract

Diffusion in FePt has been studied with emphasis on the effect of order-disorder transition by interdiffusion experiments below and above the L10-A1 transition temperature. The chemical diffusion coefficient in the disordered state obeys the Arrhenius law with the effective activation energy of 3.1 eV (1 eV = 1.6 × 10-19 J). Anisotropy of diffusion in the ordered state has been examined using monovariant single-crystals of the tetragonal L10 structure. The coefficient of diffusion in the a-axis direction is slightly lower than the extrapolation of the diffusivity from the disordered state, while that of diffusion in the c-axis direction deviates significantly toward lower values. The apparent activation energy for the diffusion in the two directions is 3.2 and 3.8 eV, respectively.