Evaluation of thickness of initial growth layer in CoCr-based perpendicular media by perpendicular torquemetry

Quantitative evaluation of the initial growth layer thickness was performed by using perpendicular torquemetry. It was clarified that: (1) The thickness of the initial growth layer becomes thicker by the increment of the content of Cr, Ta, or B additional element for CoCrPt(B,Ta) media. In the case of CoCr ₁₆Pt ₈B _x media, with increasing x from 0 to 8 at.%, the initial growth layer thickness was increased from 1.5 to 2.2 nm. In the case of CoCr ₁₆Pt ₈Ta _y media, with increasing y from 0 to 4 at.%, the initial growth layer thickness was increased from 1.5 to 4.8 nm. In the case of CoCr _zPt ₈B ₄ media, with increasing z from 16 to 24 at.%, the initial growth layer thickness was increased from 1.6 to 2.6 nm; (2) In the CoCrPtB medium, the initial growth region is relatively thin, and c-plane oriented fine grains with homogeneous columnar structure are realized. On the other hand for the CoCrPtTa medium, the initial growth region is relatively thick, and the grain size distribution and surface roughness is large due to selective grain growth; (3) The CoCrPtB magnetic film grew epitaxially on the CoCr/C/Ti underlayer. The perpendicular squareness of CoCrPtB/CoCr/C/Ti epitaxial medium was improved up to 0.88 and was maintained even for the d _mag=30nm.