CoFe-IrMn exchange-coupled soft underlayers for perpendicular media

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 mu of similar to 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 4piM(s), CoFe alloys with a high uniaxial anisotropy field H-k and a high 4piM(s) were investigated. In Co90Fe10-IrMn(10 nm) multilayer films, a significant increase in the intrinsic pinning field Hp. allowed the number of layers to be reduced from 19 to 7 with improved thermal stability. CogoFe(10)-IrMn multilayer using a thinner top layer of (Co90Fe10)N combined with a Cu-IrMn underlayer showed a unique single domain direction and a low mu of 108 up to 2 GHz but a low 4piM(s) of 15 similar to 16 kG. This was improved to similar to23 kG using Co35Fe65 films in which soft uniaxial anisotropic properties were achieved using a Cu underlayer. Co35Fe65-IrMn multilayer with the optimized structure of Glass-Cu(20 nm)-IrMn(10 nm)-[Co35Fe65(50 nm)-IrMn(10 nm)](4)-Co35Fe65(25 nm) showed outstanding characteristics for soft underlayers.