The role of NiAl underlayers in longitudinal recording media (abstract)

NiAl has been proposed as a replacement for the Cr underlayer in longitudinal recording media.1 NiAl has a B2 ordered structure with a lattice parameter close to that of Cr. Hence the same epitaxial relationships that exist in CoCrPt/Cr could also exist in CoCrPt/NiAl. Although high coercivity media have been made using a NiAl underlayer, a detailed microstructural study of the CoCrPt/NiAl is lacking. We have investigated the crystal orientation and epitaxial relationships in CoCrPt/NiAl bilayers deposited by DCM sputtering at a range of deposition temperatures up to 250 °C and sputter rates of 0.5–10 nm/s. Samples were examined by high resolution transmission electron microscopy in cross section and plan view. None of the samples showed the (002) NiAl/(1120)Co orientation that would be expected by analogy to CoCrPt/Cr films deposited at high temperatures. The CoCrPt crystals in the CoCrPt/NiAl are oriented with their c axes at a range of angles to the film plane, accounting for the lower squareness (Sq)...