Substrate roughness effect in cobalt chromium(boron, palladium, platinum, tantalum) longitudinal magnetic storage media

This work examines the influences of mechanical textures of substrate surface in the range of 2 Å to 50 Å and magnetic layer compositions on the structure and magnetic properties of longitudinal magnetic storage media. Prior to magnetic layer deposition, 460 Å thick Cr or Cr ₈₀V₂₀ underlayers with (200) texture were deposited on the Al-Mg/NiP substrates in order to facilitate epitaxial growth of (112¯0) oriented Co alloy magnetic layer. Magnetic layers were based on Co alloy films with ternary and quaternary additions of Pt, Pd, Ta, and B. The crystallographic orientation, magnetic properties and surface morphology of the films were investigated using x-ray diffraction, vibrating sample magnetometry and atomic force microscopy, respectively.; Direct-current (DC) magnetron thin film deposition conditions favoring the growth of (200) textured Cr film and subsequent epitaxial growth of (112¯0) textured Co alloy layer were first determined. Use of Cr₈₀V ₂₀ underlayer, in general, reduced lattice misfit with the magnetic layer and increased the magnetic film coercivities.; Substitution of 4.5 at.% Co with Pd or Pt in Co₈₃Cr₁₇ film reduced the coercivity and increased exchange coupling between grains. Though, the lattice dilations were similar and the grain size was smaller, the coercivity of Co_78.5Cr₁₇Pd_4.5 film was lower than that of Co_78.5Cr₁₇Pt_4.5 film. Ta and Cr on the other hand tended to decrease the exchange coupling and increase coercivity. Substitution of 2 at.% Co with B in Co₈₃Cr ₁₇ film resulted in a small increase in exchange coupling and a large decrease in coercivity. However, B addition to Co_78.5Cr ₁₇Pt_4.5 film increased the coercivity.; The coercivity, ratio of coercivities in the circumferential and radial directions, and remanent-thickness product increase with the substrate surface roughness in the roughness range of 2 Å to 10 Å. The Co_75.5 Cr₁₇Pt_4.5Ta₃ films deposited on the 2 Å, 4 Å, 10 Å, and 50 Å rough substrates show that exchange coupling decreases with surface roughness in the range of 50 Å to 4 Å and increases on further decrease of roughness to 2 Å.