Numerical and Experimental Study of Indentation on Nano-patterned Magnetic Disks
Date Issued
2015
Date
2015
Author(s)
Wu, Wei
Abstract
Bit-patterned media (BPM) is considered as a potential technology to increase recording areal density of magnetic recording; however, since the surface of BPM is discrete, it may confront more tribological challenges than conventional continuous media (CM). Consequently, it is a rather crucial issue of the contact phenomena on nano-structures. In this study, we conduct nanoindentation tests on a prototype disk sample, which contains both BPM and CM regions, by TI-950 TriboIndenter. The surface topography of the disk was measured by AFM, and is used to create finite element model. We repeated the nanoindentation tests multiple times, and confirmed the results were repeatable. The results show that CM has a larger rigidity than BPM, and that BPM has residual deformation after indention. We conduct three-dimensional (3D) static finite element analysis to study the contact behavior during nanoindentation tests on continuous and patterned elastic-plastic layered media. At first, we compared the numerical results with experimental results and found that those results are consistent. Secondly, we change the geometry properties of nano-bits in numerical model and study the influences on contact behavior. While changing the width of nano-bits, it shows that the plastic deformation in disk is reduced by increasing the width of nano-bits. While changing the height of nano-bits, the reduction of height of nano-bits by filling diamond-like carbon (DLC) can decrease the magnitude of plastic deformation, but it cannot eliminate residual deformation completely unless the disk is fully planarized with filling materials. Increase of the height of nano-bits by removing materials significantly reduces the contact pressure, and at a particular critical height, the contact pressure on nano-bits is lower than that of the fully planarized one. At last, we compared the contact behavior between the conventional continuous media and BPM planarized by DLC. The results show that the contact behaviors of those are very close. Therefore, we can regard the planarization as a method to solve the tribological problems of BPM in disk design process.
Subjects
Head-disk interface (HDI)
magnetic recording
bit-patterned media
nanoindentation
Type
thesis
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