• Journal of Magnetics
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• v.6 no.4
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• pp.109-118
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• 2001

A computer simulation, utilizing the Landau-Lifshitz-Gilbert equation, of ultra-high- density recording on continuous longitudinal media is carried out. The two important features of this work are the use of a planar-type head, which enables a high write field of 14183 Oe ts be generated at the center of the recording medium, and the media with very high coercivities up to 13010 Oe. From a systematic investigation, it is found that the optimum write field is higher than the medium coercivity by only 3400 Oe over a wide coercivity range. This new finding allows one to write an a medium with a very high coercivity by using a planar-type head. It is demonstrated that a reasonably good bit pattern with a bit density of 605 kfci is generated on the medium with a coercivity of l1720 Oe, and, combined with a high track pitch density of 100 ktpi, a recording density of 60 Gb/in$^2$can be obtained in a single layer medium. With an improved write- head designs even a higher recording density of 75 Gb/in$^2$may be possible since comparison of the results for the bit pattern from the present head profile and the ideal Lindholm profile indicates an increase in the track pitch density of about 27%. Even at this density, the thermal stability parameter (KV/kT) at room temperature is high enough (60) to provide ample room for thermal stability.

• Korean Journal of Optics and Photonics
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• v.13 no.3
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• pp.215-222
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• 2002

Using an in-situ ellipsometer, we monitored the growth curve of optical recording media in real time. For confirmation of the thickness control using in-situ ellipsometry, we analyzed the deposited multi-layer sample made of Ge-Sb-Te alloy film and ZnS-Si0$_2$ dielectric films using an exsitu spectroscopic ellipsometer. The target material in the first sputtering gun is ZnS-SiO$_2$ as the protecting dielectric layer and that in the second gun is Ge$_2$sb$_2$Te$_{5}$ as the receding layer. While depositing ZnS-SiO$_2$, Ge$_2$Sb$_2$Te$_{5}$ and ZnS-SiO$_2$ films on c-Si substrate in sequence, we measured Ψ $\Delta$ in real time. Utilizing the complex refractive indices of Ge$_2$Sb$_2$Te$_{5}$ and ZnS-SiO$_2$ obtained from the analysis of spectroscopic ellipsometry data, the evolution of ellipsometric constants Ψ, $\Delta$ with thickness is calculated. By comparing the calculated evolution curve of ellipsometric constants with the measured one, and by analyzing the effect of density variation of the Ge$_2$Sb$_2$Te$_{5}$ recording layer on ellipsometric constants with thickness, we precisely monitored the growth rate of the Ge-Sb-Te multilayer and controlled the growth process. The deviation of the real thicknesses of Ge-Sb-Te multilayer obtained under the strict monitoring is post confirmed to be less than 1.5% from the target structure of ZnS-SiO$_2$(1400 $\AA$)IGST(200 $\AA$)$\mid$ZnS-SiO$_2$(200$\AA$).(200$\AA$).

• Transactions of the Society of Information Storage Systems
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• v.3 no.2
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• pp.54-58
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• 2007

Using metal/Si materials as a recording layer, we have achieved good results for a SR disc (super resolution disc). Mainly by controlling metal composition and the ratio of metal to Si of recording layer, signal qualities were greatly enhanced. At the mark length of 75nm, the best CNR (Carrier to Noise Ratio) was about 45dB. Write power was reduced down to about 6.5mW. LFN (Low Frequency Noise) could also be reduced down to 14dB. Single tone pattern jitters for every mark whose length is from 2T through 8T were achieved to be below 10%. The readout signal was stable sustaining CNR>40dB during about 15,000 times reading. The so-called "3T-problem" could be avoided.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2000.07a
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• pp.208-211
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• 2000

We prepared Co-Cr-Ta and Co-Cr-Ta/Ti thin film for perpendicular magnetic recording media by facing targets sputtering system (FTS system). Ti underlayer effects on crystallographic and magnetic characteristics of Co-Cr-Ta perpendicular magnetic recording media have been investigated. Crystallgraphic and magnetic characteristic of prepared thin films were evaluated by x-ray diffractometry(XRD), vibrating sample magnetometer(VSM) and kerr hysteresis loop measurement. The coercivity and anisotropy field increase by introduced Ti underlayer when substrate temperature is higher than 150$^{\circ}C$. The c-axis dispersion angle and grain size of Co-Cr-Ta/Ti thin film is decrease than Co-Cr-Ta when substrate temperature is higher than 100$^{\circ}C$. Consequently, the use of a Ti underlayer highly orientated can be improved crystallographic and magnetic characteristics of Co-Cr -Ta perpendicular media layer.

• Proceedings of the Korean Magnestics Society Conference
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• 2002.12a
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• pp.234-235
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• 2002

NdFeB 박막자석은 Sputtering, MBE, Laser ablation법에 의해 제조되고 있으며[1-3] milli-size motor[4], magnetic recording media[5], micro-patterning[3]등에 응용될 수 있다. 최근에는 MEMS(Micro-electro mechanical system)분야에서도 잠재적 응용가능성을 지니고 있는 것으로 알려져 있다. 최근에는 NdFeB 박막 제조 시 자성층의 산화방지 및 자기 특성을 향상을 위하여 buffer layer를 이용한 많은 연구가 이루어지고 있다.[6] (중략)

• Proceedings of the Korean Magnestics Society Conference
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• 1998.05a
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• pp.26-27
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• 1998

• Proceedings of the Korean Magnestics Society Conference
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• 1993.03a
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• pp.84-85
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• 1993

• Proceedings of the Korean Magnestics Society Conference
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• 1999.10a
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• pp.138-139
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• 1999

• Proceedings of the Optical Society of Korea Conference
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• 2002.11a
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• pp.196-197
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• 2002

• The Transactions of the Korean Institute of Electrical Engineers
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• v.40 no.3
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• pp.258-265
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• 1991

In this paper, perpendicular magnetic recording system which consists of a single pole head and a double layer medium has been analyzed by using 2D-finite element method and preisach model for describing hysteresis characteristics. To verify the validity of this method, we compare the calculated magnetic field intensity which is above the isolated transition of magnetization with scaled up experimental data published in reference [7]. The results show good agreements within 7% error bounds and it is therefore concluded that this method will be very useful to analyze perpendicularmagnetic recording system with hysteresis characteristics.