Improving cobalt alloy thin film media through novel engineering of underlayers

The underlayer plays an important role in the longitudinal magnetic recording medium because (1) it can induce a preferred crystalline orientation in the Co alloy layer by grain-to-grain epitaxy, and (2) it can control the grain size and influence the grain isolation of the Co alloy layer. We are interested in searching for ways of changing the underlayer to improve the in-plane magnetic properties of the Co alloy thin film.; Two intermetallic phases with the B2 structure, NiAl and FeAl, and a BCC Cr alloy, CrMn, were chosen for underlayer materials in this investigation.; The sputter deposited NiAl and FeAl underlayers with the B2 structure were found to have smaller grain size, and stronger (112) lamellar textures as compared to a similarly deposited Cr film.; Recognizing that these B2 underlayers have useful crystallographic textures and small grains but the overlying Co layers do not have expected high coercivities, we added an extra thin layer, called an intermediate layer, between the magnetic layer and its underlayer. (This is the first time such a scheme has been used in thin film media.) A significant improvement of the in-plane coercivity of the CoCrPt/NiAl and CoCrPt/FeAl films was found when a thin Cr intermediate layer was placed between the CoCrPt and its B2 underlayer. Not only did the intermediate layer not disrupt the (1010)/(112) epitaxy but it slightly improved it. Higher coercivities were attributed to the better (1010) Co texture and the interdiffusion of Cr from the intermediate layer to the magnetic layer.; Sputter deposited MgO seed layers were found to be able to induce strong (002) texture in Cr, NiAl and FeAl films even without using substrate heating. While the CoCrPt/Cr and CoCrPt/NiAl films' coercivities were significantly increased because of the MgO seed layers, the coercivity of the CoCrPt/FeAl film decreased when the MgO seed layer was employed.; The CrMn underlayers were also found to induce high coercivities of the CoCrPt medium if the films were deposited on preheated substrates. There was no improvement in the coercivity if the substrates were not heated during the films' deposition. Although varying the Mn addition does not change the lattice constant of the Cr alloy, the Mn content of the CrMn underlayer affects the coercivity. We have found that a CrMn alloy underlayer with a high Mn content but not high enough to form a second phase in the film is preferred. Since we have not found any obvious correlation between the high coercivity of the CoCrPt/CrMn film and its (1120) texture, it is believed that perhaps the grain boundary segregation within the CoCrPt film caused by the interdiffusion of Mn from the underlayer plays an important role for the coercivity increase. (Abstract shortened by UMI.)...