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Recording physics, design considerations, and fabrication of bit-patterned magnetic medium for next generation data storage systems is presented. (Co/Pd)N magnetic multilayers are evaluated as candidates for bit-patterned medium recording layer materials for their high and easily tunable magnetic anisotropy. The optimized patterned multilayers used in this study had coercivities in excess of 12-14 kOe. Bit patterning was accomplished using ion-beam proximity printing, a high-throughput direct write lithography where a large array of ion beamlets shaped by a stencil mask is used to write an arbitrary device pattern. It is found that the nature of magnetization reversal strongly depends on bit edge imperfections and is likely to contribute to switching field distribution.

Recording physics, design considerations, fabrication, and characterization of bit-patterned magnetic medium for next generation data storage systems is presented. (Co/Pd) N magnetic multilayers are evaluated as candidates for bit-patterned medium recording layer materials for their high and easily tunable magnetic anisotropy. Optimized patterned multilayers used in this study had coercivities in excess of 12-14 kOe. Bit patterning was accomplished using ion-beam proximity printing, a high-throughput direct write lithography where a large array of ion beamlets shaped by a stencil mask is used to write an arbitrary device pattern. It is found that the nature of magnetization reversal strongly depends on bit edge imperfections and is likely to contribute to switching field distribution.

An approach to fabrication of a patterned magnetic recording medium for next generation data storage systems is presented. (Co/Pd)n magnetic multilayers are evaluated as candidates for patterned medium materials for their high and easily controllable magnetic anisotropy. The multilayer films deposited on a Ta seed layer enable high intergranular exchange coupling—an essential feature of a patterned magnetic recording medium. The quality of (Co/Pd)n superlattices was optimized via deposition conditions and monitored using low-angle x-ray diffraction. An estimated in-plane (hard-axis) magnetization saturation field in excess of 40 000 Oe was observed. Vertical (easy-axis) hysteresis loops for as-deposited continuous magnetic multilayers exhibited a low coercivity of 930 Oe, indicating highly uniform (magnetically) films with weak domain wall pinning. Ion-beam proximity lithography was used to pattern magnetic multilayers into 43 nm islands on a 135 nm pitch. Following patterning, easy-axis coercivity increased nearly 15-fold to 12.7 kOe.

We describe the fabrication of large-area magnetic ring structures using ion beam proximity lithography (IBPL) to pattern an array of circular openings and then use a conforming oxide coating to define the ring structure through the sidewall coating. Arrays of Permalloy rings with sub 500 nm outer diameter and 150 nm inner diameter on a 650 nm pitch over a 5.5 mm times 6 mm area were fabricated to study transitions between the micromagnetic configurations within these structures. The results suggest that the field required for onion-to-vortex transition and field required for vortex-to-onion transition to be 0Oe and 400Oe, respectively.

We describe a self-limiting, low-energy argon-ion-milling process that enables noncircular device patterns, such as squares or hexagons, to be formed using precursor arrays of uniform circular openings in poly(methyl methacrylate) defined using electron beam lithography. The proposed patterning technique is of particular interest for bit-patterned magnetic recording medium fabrication, where square magnetic bits result in improved recording system performance. Bit-patterned magnetic medium is among the primary candidates for the next generation magnetic recording technologies and is expected to extend the areal bit density limits far beyond 1 Tbit/in 2 . The proposed patterning technology can be applied either for direct medium prototyping or for manufacturing of nanoimprint lithography templates or ion beam lithography stencil masks that can be utilized in mass production.

We describe the lithographic structuring of large-area patterned medium samples with sub-50 nm features using ion beam proximity lithography (IBPL). The quality of the patterns formed in IBPL system is primarily limited by the quality of the stencil masks. Hence, the emphasis of this work has been to develop a reliable mask fabrication process that can achieve a size uniformity that is suitable for patterned media. We have developed a mask fabrication approach that incorporates palladium as a hard mask for transferring the lithography pattern through a silicon nitride membrane. A conformal gold coating allows for further reduction of the mask features without a significant increase in the feature size variation. An average standard deviation of 3 nm and 5 nm was measured during various steps of the stencil mask fabrication and after printing using IBPL in PMMA resist, respectively. Patterned medium prototypes with features ranging from 40 nm to 300 nm have been fabricated and magnetic properties measured. A 6-12 fold increase in coercivity was measured for multilayer samples after patterning. Ion irradiation of patterned multilayer samples was also studied as a means to control magnetic anisotropy as well as to evaluate possible ion irradiation damage involved in ion-beam proximity lithography patterning. Patterned multilayer samples show a decrease in coercivity from 11 kOe for as-patterned to 0.3 kOe for 800 muC/cm2 and suggests that ion irradiation can be an integral part of bit patterned medium fabrication for anisotropy control.