Topological bumped surface induced by the lattice extension of the RuCr intermediate layer for granular-type perpendicular recording media

Surface roughness caused by the grain growth of the RuCr non-magnetic intermediate layer (NMIL) was evaluated using the X-ray total reflection method. In the case of Ru NMIL, the value of root mean square roughness of NMIL (σ) increases from 0.59 to 1.45 nm with increase in Ar gas pressure and/or thickness of the Ru layer. Judging from the loop slope and normalized coercivity, the degree of magnetic isolation increases as σ increases, independent of the Cr content of a RuCr NMIL. Furthermore, it was found that σ of NMIL is strongly correlated with wettability to the seed layer material and is enhanced by the lattice extension of NMIL.