Exchange-biased CoTaZr soft underlayer for perpendicular recording

As a way of controlling the domain structure of a soft magnetic underlayer, we introduced a Pd/antiferromagnetic-MnIr/CoFe trilayer below a CoTaZr soft magnetic underlayer in perpendicular recording media, and we examined the effect of exchange biasing on the spike noise. Films consisting of layer structure-Pd (5 nm thick)/MnIr (7.5 nm)/CoFe (1-10 nm)/CoTaZr (50-200 nm)-were sputter deposited on precoated glass disks. The Fe content in the CoFe layer was varied from 5 to 70 at. %. After deposition, the films were heated to 250 degreesC and cooled in a magnetic field. Both uniaxial and unidirectional anisotropies were induced along the radial direction of the disk. It was found that the Pd layer promoted a face-centered-cubic-MnIr (111) crystalline texture, while the CoFe layer enhanced the exchange bias field H-ex by 1.5-3.2 times, compared with that in the case of a Pd/MnIr/CoTaZr film. The value of H-ex was strongly dependent on the CoFe alloy composition. By using the Pd/MnIr/Co60Fe40 trilayer, spike noise was suppressed when the thickness of the CoTaZr layer ranged from 50 to 200 nm. This suppression is probably due to the fact that the exchange biasing restrained the formation of domain walls in the CoTaZr layers. (C) 2003 American Institute of Physics.