Effects of Mn- and Zr-doped CrMo double underlayers on structure and magnetic properties of CoCrPtB longitudinal media

The addition of 2% Zr into the CrMo underlayer reduced the grain size of the recording layer to 5.33 nm and achieved a narrow distribution of grain size. The addition of 5% Mn into the CrMo underlayer enhanced the crystallographic texture and coercivity. To obtain both advantages of Zr and Mn doping effects, the Zr and Mn doped double underlayer were introduced in longitudinal media. The magnetic properties and microstructures of the recording layers on CrMoMn-CrMoZr and CrMoZr-CrMoMn double underlayers mainly depended on the underlayer adjacent to the CoCr layer, whereas the underlayer on NiP further modified the characteristics of the recording layers. By combining the CrMoMn and CrMoZr double underlayers, longitudinal media revealed enhanced coercivity, small intergranular coupling, and a narrow distribution of grain size.