AVS 46th International Symposium
    Magnetic Interfaces and Nanostructures Technical Group Monday Sessions
       Session MI+VM+AS-MoA

Invited Paper MI+VM+AS-MoA7
Crystallographic Texture and Stress in Co-Based Magnetic Recording Media and Underlayers

Monday, October 25, 1999, 4:00 pm, Room 618/619

Session: Magnetic Recording: Media and Heads
Presenter: B.M. Clemens, Stanford University
Authors: B.M. Clemens, Stanford University
G. Khanna, Stanford University
Correspondent: Click to Email
The magnetic and recording properties of Co-based media are a strong function of crystallographic texture and stress in the media layers, which are in turn strongly influenced by the texture and stress of the Cr underlayer. The anisotropy in strain and the distribution of c-axes in the hcp Co alloy media can determine the magnetic hysteresis anisotropy through magnetostrictive and magnetocrystalline effects. The processing conditions and mechanical texture grooves in the NiP/Al substrate strongly influence the microstructural and mechanical properties of the Cr and Co films. We report x-ray studies of the texture and strain in Cr and Co-based films sputter deposited over a range of temperatures and substrate biases on smooth and mechanically textured substrates. All films showed an in-plane compressive stress. The magnitude of the stress in Cr and Co films grown without a substrate bias decreases with decreasing growth temperature, consistent with thermal mismatch stress. The stress in the Cr films grown with a -300V bias was greater than that of unbiased films, and independent of growth temperature. This suggests that the bias-induced stress is close to the yield stress of the film. However, the biased Co films show a decrease in compressive stress with decreasing temperature. For mechanically textured substrates, the stress measured in the direction perpendicular to the texture grooves was less compressive relative to the parallel direction in both Cr and Co. However, the stress anisotropy vanishes in smooth substrates. A simple strain relaxation model is used to explain the observed Cr stress values in the textured disks. The anisotropic strain in the Cr may also account for the observed preferential alignment of Co c-axes along the grooves. Calculation of the magnetoelastic and magnetocrystalline energies predicts that Co stress anisotropy and the preferential alignment of Co c-axes along the grooves both contribute to the observed hysteresis anisotropy.