The effects of B2 structured underlayers on thin film magnetic recording media

It is well known that underlayers have profound effects on the magnetic pro perties of longitudinal thin film media. These effects are derived from the underlayer's influence on the structural features of the magnetic media su ch as crystallographic texture, grain size and grain isolation. Pure Cr has been the most popular underlayer for Co alloy thin films for more than two decades mainly because Cr underlayers can enhance the c-axis in-plane crys tallographic texture of the overlying Co alloy thin films, Many investigato rs have studied alternative underlayers and have achieved various degrees o f success. However, those underlayers are seldom different from the BCC str ucture or are Cr with various alloying additions. We have studied NiAl and FeAl underlayers with the B2 ordered structure (CsCl prototype) which have lattice constants similar to that of Cr. Rf diode sputter deposited NiAl an d FeAl films were found to ha ve the B2 structure and have a smaller grain size and more uniform equiaxed grains compared to that of a similarly depos ited Cr film. X-ray diffractometry studies showed that CoCrPt films grown o n NiAl or FeAl underlayers tend to have the (10 (1) over bar 0) crystallogr aphic texture with a better in-plane c-axis orientation than CoCrPt films g rown on Cr underlayers. The in-plane coercivities of the CoCrPt/NiAl and Co CrPt/FeAl films can be significantly improved by inserting a thin intermedi ate layer of Cr between the CoCrPt and its underlayer. Cr, NiAl and FeAl un derlayers are found to have a strong (002) crystallographic texture when sp utter deposited MgO seed layers are used. The MgO seedlayers increase the c oercivities of the CoCrPt films having Cr or NiAl underlayers hut decrease the coercivities of the CoCrPt films having FeAl underlayers. (C) 1998 Else vier Science Ltd. All rights reserved.