Compositional dependence of Cr_(100-x)Ti_x texture-inducing layer underlying (002) textured bcc-Cr alloy seed layer for FePt-C based heat-assisted magnetic recording media

摘要

Cr_(100-x)Ti_x amorphous texture-inducing layers (TIL) were investigated to realize highly (002) oriented Ll_o FePt-C granular films through hetero-epitaxial growth on the (002) textured bcc-Cr_(80)Mn_(20) seed layer (bcc-SL). As-deposited TILs showed the amorphous phase in Ti content of 30 ≤ x (at) ≤ 75. Particularly, films with 40 ≤ x ≤ 60 kept the amorphous phase against the heat treatment over 600℃. It was found that preference of the crystallographic texture for bcc-SLs is directly affected by the structural phase of TILs. (002) crystallographic texture was realized in bcc-SLs deposited on the amorphous TILs (40 ≤ x ≤ 70), whereas (110) texture was formed in bcc-SLs overlying on crystalline TILs (x 70). Correlation between the angular distribution of (002) crystal orientation of bcc-SL evaluated by full width at half maximum of (002) diffraction (FWHM) and a grain diameter of bcc-SL indicated that while the development of the lateral growth for bcc-SL grain reduces FWHM, crystallization of amorphous TILs hinders FWHM. Ll_o FePt-C granular films were fabricated under the substrate heating process over 600 ℃ with having different FWHM of bcc-SL. Hysteresis loops showed that squareness (M_r/M_s) of the films increased from 0.87 to 0.95 when FWHM of bcc-SL decreased from 13.7° to 3.8°. It is suggested that the reduction of (002) FWHM affects to the overlying MgO film as well as FePt-C granular film by means of the hetero-epitaxial growth.