INTERGRAIN MAGNETIC COUPLING AND MICROSTRUCTURE IN COPTCR, COPTCRTA, AND COPTCRB ALLOYS

We have investigated intergrain magnetic interactions in three types o f Co-based alloys of interest for longitudinal magnetic recording: CoP tCr, CoPtCrTa, and CoPtCrB. The goal is to quantify how intergranular exchange interactions in CoPtCr alloys are modified by doping said all oys with additives such as Ta and B. These 20-nm-thick alloys were gro wn under identical deposition conditions on AlMg/NiP substrates and a comprehensive study of their microstructural and magnetic properties w as conducted to evaluate the degree of intergranular exchange coupling and the manner how the coupling depends on the corresponding microstr uctural properties. We find that the ternary alloy exhibits the strong est intergrain coupling. In the case of the quaternary alloys, the deg ree of exchange interactions is virtually the same. Consequently, any significant difference pertaining recording performance in these quate rnary alloys must be dominated by the inherent differences in grain mi crostructure and the spatial distribution of the alloy constituent ele ments. (C) 1998 American Institute of Physics. [S0021-8979(98)04323-0] .