• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 1999.11a
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• pp.419-422
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• 1999

We prepared CoCr thin film for perpendicular magnetic recording media by facing targets sputtering system(FTS system) which can deposit a high quality thin films in plasma-free state and wide range of working pressure. In this study, we investigated that the effect of sputtering condition , that Argon gas pressure and substrate temperature, on magnetic and crystallographic characteristic of CoCr thin film as well as the variation perpendicular coercivity in changing of film's thickness. Crystallographic and magnetic characteristic of prepared thin films were evaluated by x-ray fractometry(XRD), vibrating sample magnetometer(VSM) and kerr hysteresis loop measurement.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2001.11b
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• pp.77-80
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• 2001

Crystallographic and magnetic characteristics of CoCr-based magnetic thin film for perpendicular magnetic recording media were influenced on preparing conditions. In these, there is that substrate temperature was parameter that increases perpendicular coercivity of CoCrTa magnetic layer using recording layer. While preparation of CoCr-based doublelayer, by optimizing substrate temperature, we expect to increase perpendicular anisotropy of CoCr magnetic layer and prepare ferromagnetic recording layer with a good quality by epitaxial growth. CoCrTa/Si doublelayer showed a good dispersion angle of c-axis orientation $\Delta\theta_{50}$ caused by inserting amorphous Si underlayer which prepared at underlayer substrate temperature 250C. Perpendicular coercivity was constant, in-plane coercivity was controlled a low value about 200Oe. This result implied that Si underlayer could restrain growth of initial layer of CoCrTa thin film, which showed bad magnetic properties effectively without participating magnetization patterns of magnetic layer. In case of CoCrTa/Si that prepared with ultra thin underlayer, crystalline orientation of CoCrTa was improved rather underlayer thickness 1nm, it was expected that amorphous Si layer played a important role in not only underlayer but also seed layer.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.19 no.9
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• pp.883-887
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• 2006

In order to attain high-rate deposition of Mn-Zn ferrite thin film for soft magnetic underlayer in perpendicular magnetic recording media, a reactive sputtering using powder-metal targets under the mixture gas of Ar and $O_{2}$ was performed. It was succeeded that Mn-Zn ferrite films with (111) crystal orientation were deposited on Pt(111) underlayer without any annealing process. The film revealed 3.4 kG of 4 ${\pi}Ms$, 70 Oe of coercivity. The deposition rate of the new method was 16 times as high as that of the conventional method using ferrite target.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 1988.10a
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• pp.46-46
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• 1988

Structural and magnetic properties of Co-Cr-Mo films were investigated in connection with sputtering conditions. Films were prepared using a convention RF sputtering system. X-ray diffractometry, scanning electron microscopy and transmission electron microscopy were employed to investigate structure properties. Vibrating sample magnetometry was used for coercivity and saturation magnetization measurements. Co-Cr-Mo films displayed reasonable values of perpendicular coercivity and saturation magnetization for perpendicular recording media and showed good perpendicular orientation of the hcp c-axis to the film surface. Perpendicular coercivity was strongly dependent upon substrate technique showed better c-axis orientation than hose using the stationary substrate. Co-Cr-Mo films of 2.9 at. % Mo content showed maximum perpendicular coercivity and saturation magnetization. The films deposited at lower Ar pressure showed good magnetic properties. There was no explicit relationship between the columnar structure and c-axis orientation. Co-Cr-Mo films was found to have suitable structural and magnetic properties for perpendicular recording media.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 1997.11a
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• pp.309-312
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• 1997

The Ce-Cr(-Ta) film are one of the most suitable candidates for perpendicular magnetic media. the control of the preparation conditions, such as Ar gas pressure P$\_$Ar/ substrates temperature T$\_$s/, films thickness $\delta$, deposition speed R$\_$d/, is considered to be important to attain ultra high density recording far perpendicular magnetic recording media. In this study, the Co-Cr thin films and Co-Cr-Ta thin films were deposited on the glass side substrates by using Facing Targets Sputtering apparatus(FTS). Crystallographic characteristics and magnetic characteristics were evaluated by X-ray diffractometry(XRD), Vibrating Sample Magnetometer(VSM) respectively.

• Journal of the Korean Magnetics Society
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• v.5 no.5
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• pp.690-694
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• 1995

Reducing media noise is a key to realizing high areal recording density. However, perpendicularly oriented Co-Cr films, stong candidates for high density recording media, have received little attention in terms of recording noise. We studied the noise characteristics of Co-Cr based alloy films by varying the compositionally separated structure. Co-Cr films with fine compositionally separated microstructure were observed to have low noise, which recording density dependence were negative or week. Studies on control of the microstructure and magnetic properties in combination with noise analysis are important to realize high density recording media.

• Journal of Magnetics
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• v.7 no.3
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• pp.115-125
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• 2002

We proposed a novel method to evaluate the magnetic properties of the initial layer and the columnar structure separately for CoCr-based perpendicular recording media. We show that the thickness of the initial layer and the intrinsic magnetocrystalline anisotropy of columnar structure can be quantitatively evaluated using the plotted product of perpendicular anisotropy to magnetic film thickness versus magnetic film thickness ($K_{u{\bot}}^{ex{p.}}$ $\times$ d$_{mag.}$ vs. d$_{mag.}$ plot). Based on the analyses, it is found that: (1) compared with CoCrPtTa media, CoCrPtB media have relatively thin initial layer, and have fine grains with homogeneous columnar structure with c-plane crystallographic orientation; (2) CoCrPtB media can be grown epitaxially on Ru or CoCr/C intermediate layer, and as the result, the magnetic properties of the media within thin thickness region of d$_{mag.}$ $\leq$ 20 nm is significantly improved; (3) the key issue of material investigation for CoCr-based perpendicular recording media will be focused on how to fabricate c-plane-oriented columnar grains well isolated with nonmagnetic substance in epitaxial-growth media, while maintaining the thermal stability of the media.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2005.05a
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• pp.92-95
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• 2005

The silver photodoping effect in amorphous AsGeSeS chalcogenide thin films for holographic recording has been investigated using a HeNe laser ($\lambda$=632.8 nm). The chalcogenide films prepared in this work were thinner in comparison with the penetration depth of recording light ($d_p$=1.66 mm). The variation of the diffraction efficiency $(\eta)$ in amorphous chalcogende films exhibits a tendency, independently of the Ag photodoping. That is, n increases relatively rapidly at the beginning of the recording process, reaches the maximum $({\eta}_{max})$ and slowly decreases. In addition, the value of ${\eta}_{max}$ depends strongly on chalcogenide film thickness(d) and its peak among the films with d = 40, 80, 150, 300, and 633 nm is observed at d = 150 nm (approximately 1/2n), where n is refractive index of the chalcogenide (n=2.0). The ${\eta}$ is largely enhanced by Ag photodoping into the chalcogenides. In particular, the value of hmax in a bilayer of 10-nm-thick Ag/150-nm-thick AsGeSeS film is about 1.6%, which corresponds to ~20 times in comparison with that of the AsGeSeS film (without Ag).

• Journal of Magnetics
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• v.18 no.2
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• pp.86-89
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• 2013

This paper shows a new effective approach to measure crystallization temperature of soft magnetic underlayer (SUL) for next generation of heat assisted perpendicular recording media. This approach uses temperature dependent reflectivity, which shows a clear jump when samples are crystallized. To achieve this measurement, an optical system is set up using hot plate and infrared laser. Reflectivity of SUL $(Co_{70}Fe_{30})_{92}Ta_3Zr_5$ shows a clear jump at its amorphous-crystalline transition temperature. Experiment results show this effect is clear in infrared region, and is weak for visible light.

• Journal of Magnetics
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• v.5 no.4
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• pp.143-146
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• 2000

In this study, the magnetic properties of CoCrPt films (far longditudinal recording) on a novel VMn underlayer were measured and compared with similar films on conventional Cr underlayers. It was found that the VMn film had (200) preferred orientation and the lattice constant was about 0.2967 nm, which is slightly larger than that of the Cr film, 0.2888 m. The grain size of the VMn film was 9.8 nm at 30 m thickness, about 39% smaller than that of a similarly deposited Cr. The CoCrPt/VMn films showed higher coercivity in comparison with the CoCrPt/Cr films. The coercivity increase is attributed to the increased Co (11.0) texture, improved lattice matching between Co (11.0) and VMn (200), and lower stacking fault density. V or Mn must have diffused into the CoCrPt magnetic layer uniformly rather than preferentially along grain boundaries. This reduced Ms at higher substrate temperature.