Grain Size Reduction by Doping Cr Underlayer with Ru for Longitudinal Magnetic Recording Media

A Cr underlayer was doped with 10 at. % Ru to enlarge the Cr lattice and promote the Co(11.0) formation of the CoCrPtTaB magnetic layer by in-plane tensile stress at a recording layer/underlayer interface. The texture, grain size and magnetic characteristics of CoCrPtTaB/Cr(Ru) were examined as well. The CrRu(002) underlayer exhibit markedly enhanced Co(11.0) orientation, increasing coercivity and preferential alignment of the $c$-axis. The grain size and grain size distribution of the recording layer decreased as the CoCrPtTaB magnetic layer grew epitaxially on the CrRu underlayer. The grain size of the recording layer was reduced from 11.2 nm with a pure Cr underlayer to 5.4 nm with a CrRu underlayer. The latter is the smallest grain size yet reported for CoCr-based alloy recording media.