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Diamond-like carbon (DLC) coatings were deposited using a commercial direct ion beam deposition technique on thin-film Al2O3–TiC inductive write heads. The coating thicknesses used were 5, 10, and 20 nm. Accelerated wear tests were conducted with metal particle tapes in a linear tape drive. Atomic force microscopy was used to image the thin-film regions to measure pole tip recession (PTR), relative wear of the pole tip with respect to the air bearing surface. It is found that the coating wears off of the head substrate to a significant extent in the first 1000 km of sliding distance. The coating is worn off the substrate long before it wears off of the thin-film region. The existence of the coating on the thin-film region provides close enough wear characteristics between the substrate and thin film that the two wear at similar rates. This results in little growth in pole tip recession. Early in the wear test, the coated substrate wears at a slightly higher rate than the DLC coated thin-film region due to the difference in tape contact pressure between the two materials; decreasing PTR is the result. As the coating on the substrate wears significantly, PTR begins to increase with sliding distance. Failure does not actually occur until the coating has worn off of the thin-film region. Near failure, the coating delaminates locally. Results indicate that coatings of 20 nm thickness may provide protection against PTR in future tape drives.

Magnetic tapes, which may be modeled as three-ply laminates, exhibit transverse curvature, or cupping, as manufactured and when mechanical and hygrothermal loads are applied. Among other things, this cupping affects debris generation since it influences the contact between the flawed tape edge and head, the point where much of the debris generation occurs. This influence on debris generation is demonstrated experimentally in this study. Much more debris accumulates near the tape edge-head contact than at other contact locations. No difference in debris generation was found for two tapes with slightly different residual cupping (which is controlled during manufacturing). The target residual cupping is usually negative, which means that the tape bows out towards the tape so that the edges are farther away from the head than the center of contact is, so as to reduce contact pressure with the tape edges. However, cupping generally changes upon application of a tension and generally reduces the importance of residual cupping, which accounts for the failure to find a difference in debris generation for tapes with slightly different residual cupping. A finite element method model that uses laminate shell elements and accounts for in-plane stress stiffening, thus making it suitable for thin laminate modeling, was created. This modeling demonstrates that application of tensile and normal (used to simulate head contact) loads leads to cupping movement in the positive direction, which indicates a more severe edge contact, for an increase in front coat Young’s modulus and/or an increase in front coat thickness. The same trends hold for an increase in back coat Young’s modulus and/or an increase in back coat thickness. Modeling also demonstrates that cupping moves in the positive direction for an increase in the substrate’s Young’s modulus in the transverse direction for MP and ME tapes. An analytical model demonstrates that increases in temperature and front coat thermal expansion coefficient leads to cupping movement in the negative direction. The same trends hold for changes in relative humidity.

Pole tip recession (PTR) in linear tape heads causes an increase in spacing and consequently an increase in signal loss. In this study, PTR in linear tape drives is analysed. Functional drive tests are conducted using thin-film Al 2 O 3 ±TiC and Ni±Zn ferrite heads sliding against metal particle tape. Atomic force microscopy is used to measure PTR and the recession of the overcoat material used in the construction of the head. In measuring PTR, care must be taken in correctly orienting the stand-alone atomic force microscope tip with respect to the head sample. Care must also be taken in post-processing the raw stand-alone atomic force microscopy data. Based on PTR data with Al 2 O 3 ±TiC and Ni±Zn ferrite heads, no significant differences exist in the PTR of Al 2 O 3 ±TiC heads compared with Ni±Zn ferrite heads. In the case of the Ni±Zn ferrite head, the softer Ni±Zn ferrite substrate has mechanical properties close to those of the poles, suggesting that PTR growth should be low. However, additional third-body wear particles from the ferrite substrate result in additional pole tip wear. No significant difference is seen in the wear of Co±Zr±Ta poles and Ni±Fe poles, as they have comparable mechanical properties. No strong conclusion may be drawn about the effect of tape speed on PTR. An increase in tape tension leads to an increase in PTR. This is a result of an increase in the normal force, which causes an increase in the abrasive wear. An increase in interface contamination also leads to an increase in PTR.

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