Polarization-dependent XAFS studies on the role of Ta in the compositional segregation of Co-Cr-Ta magnetic recording media

Extended X-ray absorption fine structure (EXAFS) measurements of Ta in Co-Cr-Ta films were performed using normal glancing incident radiation in order investigate, respectively, the in-plane and out-of-plane local structure and chemistry about the Ta atom sites. The Fourier transformed EXAFS data illustrates the presence of an anisotropy between the in-plane and out-of-plane structures around the Ta atoms, indicating that the Ta atoms are incorporated in a closed-packed structure with the c-axis aligned in the plane of the film. Analysis of the local environments around Ta indicates that the Ta atoms are either randomly distributed throughout the film or have preferentially segregated to the Cr-rich regions. Results indicate that an increase in temperature results in Ta having a broader distribution of first-neighbor distances as well as a slight decrease in the number of surrounding atoms. This is consistent with a local structure model which has vacancies preferentially segregating to the Ta atoms thereby decreasing the diffusion of Cr within the grains.