CoFe-IrMn exchange-coupled soft underlayers for perpendicular media

Abstract

FeTaN-IrMn exchange-coupled multilayer films have shown outstanding characteristics as soft underlayers for perpendicular media but 19 layers including the IrMn layer were required to meet the target permeability /spl mu/ of /spl sim/100 and ferromagnetic thickness of 200 nm. In order to decrease the number of layers, to improve thermal stability, and to increase the saturation flux density 4/spl pi/M/sub s/, CoFe alloys with a high uniaxial anisotropy field H/sub k/ and a high 4/spl pi/M/sub s/ were investigated. In Co/sub 90/Fe/sub 10/-IrMn(10 nm) multilayer films, a significant increase in the intrinsic pinning field H/sub po/ allowed the number of layers to be reduced from 19 to 7 with improved thermal stability. Co/sub 90/Fe/sub 10/-IrMn multilayer using a thinner top layer of (Co/sub 90/Fe/sub 10/)N combined with a Cu-IrMn underlayer showed a unique single domain direction and a low /spl mu/ of 108 up to 2 GHz but a low 4/spl pi/M/sub s/ of 15/spl sim/16 kG. This was improved to /spl sim/23 kG using Co/sub 35/Fe/sub 65/ films in which soft uniaxial anisotropic properties were achieved using a Cu underlayer. Co/sub 35/Fe/sub 65/-IrMn multilayer with the optimized structure of Glass-Cu(20 nm)-IrMn(10 nm)-[Co/sub 35/Fe/sub 65/(50 nm)-IrMn(10 nm)]/sub 4/-Co/sub 35/Fe/sub 65/(25 nm) showed outstanding characteristics for soft underlayers.