High Anisotropy CoPtCrB Magnetic Recording Media

We describe the synthesis, magnetism and structure of CoPtCrB alloys with Pt concentrations from 10 43 %. The Cr concentration in the alloys was 15-17 % and the B concentration was 9-11 %. The magnetic anisotropy and coercivity increase with increasing Pt up to M 30%, plateau at M 35,000 Oe and w 6000 Oe, respectively, and then decrease. Transmission electron microscopy results show the media form fine, isolated grains for all Pt concentrations. X-ray diffraction measurements show that with increasing Pt an fee Co-alloy phase is progressively formed at the expense of the hcp Co-alloy and that this fraction becomes significant for > 35% Pt. The formation of the fee phase likely causes the behavior in the anisotropy. No Pt concentration dependence is observed for the stacking fault density. The X-ray data show that with increasing Pt the CoPtCrB alloy lattice parameters exhibit two distinct regions with the slope changing at 16 % Pt. The presence of these two regions is discussed. PACS numbers: 75.5O.SS, 75.30.Gw, 61.72.Dd, 68.55.Jk *Electronic address: mf toneyQslac. stanf ord. edu