Influence of various underlayers on [001] texture and magnetic properties in FePt and FexNi1 − xPt thin films

Abstract

Perpendicular magnetic recording thin films require proper crystallographic growth to ensure that the magnetic easy-axis is aligned normal to the growth plane. The texture and in situ growth stresses of (001) FePt and FexNi(1−x)Pt thin films on various underlayer combinations are studied. These were correlated with the magnetic properties allowing self consistent direct comparisons of the various parameters to be made. It was found that the (001) texture, L10 chemical ordering and perpendicular magnetic alignment was improved with the smaller lattice misfit that accompanied a combination of Pt/Cr multilayered and compositionally graded underlayers on a (001) MgO substrate. A Cr underlayer allowed the Pt film to deposit in a relatively strain-free lattice condition from which the FePt based films could grow in a similar strain-free epitaxial condition. In situ stress measurements confirmed that these underlayers reduced the intrinsic compressive growth stresses to approximately one-fifth the FePt stress value for being directly deposited onto the MgO surface. The incorporation of Ni to the (001) growth of FePt facilitated in-plane and out-of-plane c-variant growth for the L10 structure. Finally, a linear compositional gradient FexNi0.48−xPt0.52 (0<x<0.48) thin film was deposited, which exhibited good [001] orientation and perpendicular magnetic alignment. This has been proposed as a magnetic switching architecture for high density, thermally stable but switchable magnetic media grains using current write head fields.