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Quantifying delamination of a diamond-like-carbon coating on a magnetic recording head using molecular dynamics

Michael Price (University of Utah), Andrey Ovcharenko (Western Digital Corporation), Raj Thangaraj (Western Digital Corporation), Bart Raeymaekers (University of Utah)

Contact Mechanics

Tue 4:20 - 5:40

Barus-Holley 161

To increase hard drive storage density, the magnetic spacing between the read/write element in the recording head and the magnetic layer of the disk is decreased. The permalloy material in the head substrate structure is covered with an ultra-thin protective amorphous carbon (a-C) overcoat. A Si layer enhances adhesion between the permalloy and the a-C layer. Wear and delamination become increasingly important with decreasing thickness of these coatings, e.g., to accommodate a reduction of the magnetic spacing. Removal of the overcoat, even in part, may lead to corrosion of the read/write element and, thus, reduce the reliability of the head disk interface (HDI). In this work, delamination of the a-C and Si coatings of the recording head during normal loading/unloading against the disk is investigated using molecular dynamics simulations. An algorithm is developed to quantify delamination between the a-C/Si, and Si/permalloy interfaces. This algorithm measures the change in the number of interfacial bonds between two layers at an arbitrary instant, relative to the number of interfacial bonds that exist in the initial state of the system. Using this algorithm, delamination is evaluated as a function of contact pressure and thickness of the silicon adhesion layer. No permanent delamination is observed for contact pressure between the head and disk of up to 100 MPa, and for different thicknesses of the Si adhesion layer, except in the case where no silicon layer is used between the a-C layer and the permalloy substrate. The number of interfacial bonds between the Si and permalloy layer increases with increasing contact pressure and increasing thickness of the Si layer. The a-C/Si interface remains almost unaltered during the normal load/unload procedure.