• Journal of the Korean Magnetics Society
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• v.12 no.3
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• pp.94-98
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• 2002

Sputtering conditions and various underlayer such as Al, Cu, Ni, Cr, Ag, Mg, Fe, Co, Pd, Au, Pt, Mo and Hf were investigated for coercivity enhancement of 20 nm Ti/CoCrPt thin films in order to increase the coercivity of the films thinner than 20 nm. Among them, Ag and Mg were effective to increase the coercivity. Particularly 2 nm Ag was very effective to increase the coercivity and nucleation field as well as to reduce ${\alpha}$ value in CoCrPt thin film such that the coercivity of 2 nm Ag/18 nm Ti/10 nm CoCrPt film was 2200 Oe. However, it seemed that other coercivity enhancement mechanism operated in CoCrPt films because Ti (002) preferred texture was not developed with Ag underlayer contrary to a general expectation. And the coercivity and nucleation field were decreased when glass substrate with rougher surface was used.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.15 no.3
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• pp.281-286
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• 2002

In odder to investigate the magnetic properties of CoCr-based bilayered thin films on kind of underlayer, we introduced amorphous Si layer to Co-Cr(-Ta) magnetic layer as underlayer. First, we prepared CoCr and CoCrTa single layer using the Facing Targets Sputtering system to investigate theirs properties. It was revealed that with increasing the film thickness of CoCr, CoCrTa single layer, crystalline orientation and perpendicular coercivity was improved. The CoCrTa thin film showed bettor crystalline and magnetic characteristics than CoCr thin film. As a result of investigating magnetic properties of CoCr and CoCrTa magnetic layer on introducing the Si underlayer, perpendicular coercivity and saturation magnetization of CoCr/Si and CoCrTa/Si bilayered thin film were decreased due to the increased grain size and diffusion of Si atoms to magnetic layer. And they showed constant with increasing the film thickness of Si thin film. However, in case of CoCrTa/Si bilayered thin film, in-plane coercivity was controlled low at about 250Oe. The c-axis orientations of CoCr/si and CoCrTa/Si bilayered thin film showed a good crystalline characteristics as about $2^{\circ}$.

• Journal of the Korean institute of surface engineering
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• v.34 no.6
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• pp.531-536
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• 2001

Co-22 %Cr alloy films are promising for high-density perpendicular magnetic recording media with their perpendicular anisotropy and large coercivity of 3000 Oe. We observed that a self organized nano structure (SONS) of fine ferromagnetic Co-enriched phase and paramagnetic Cr-enriched phase appears inside the grain of Co-Cr magnetic alloy thin films at the elevated substrate temperature after do-sputtering. The periodic fine Co-enriched phase and Cr-enriched phase is the plate shape of 80 (equation omitted)-wide and 1000 (equation omitted)-long. Cr-enriched phases are located at the center of grains. We prepared 5000 (equation omitted) -thick Co-22 %Cr films on polyimide substrate with varying substrate temperature of $ 30^{\circ}C$, $ 150^{\circ}C$ ,200 $^{\circ}C$, $300^{\circ}C$, and $400^{\circ}C$, respectively. A transmission electron microscope equipped with energy dispersive X-ray analyzer is employed to observe the microstructure of each samples after Co-enri-ched phase are etched selectively. The self organized nano structure of Co-enriched and Cr-enriched lamellar is observed above the substrate temperture of $150^{\circ}C$. No compositional change is observed with substrate temperature. The compositional phase separation in self organized structure becomes clear as the substrate temperature increases. Our results implies that the self organized nano structure in Co-22 %Cr film is ideal for ultra high density recording media by recording selectively on Co-enri-ohed phase.

• Proceedings of the Korean Magnestics Society Conference
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• 1995.05a
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• pp.86-87
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• 1995

• Journal of the Korean Magnetics Society
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• v.3 no.3
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• pp.221-228
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• 1993

The general requirements of recording media include recording performance, environmental stability, runnability on the drive or deck, and manufacturability. CoCrMo thin films were prepared using RF sputtering system for a study on chemical stability. Surface degradation of the CoCrMo thin film was studied by SEM, XPS and AES. Surface degradation was found to be dependent of sputtering condition and Mo content. Addition of Mo to CoCr thin film improved dramatically its surface degradation resistance in dilute sulfuric acid, as indicated by active-passive transition appeared in electrochemical polarization curve. Futhermore, the passive current density was decreased with increasing Mo content. The reduction in a number density of corrosion sites by Mo addition vms observed, after accelerated corrosion test. AES survey indicated that corrosion occured on the site with Cr depletion and highly concentrated chloride ions.

• Korean Journal of Materials Research
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• v.7 no.1
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• pp.69-75
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• 1997

Thin films of $Si0_2(1000{\AA})/CoNiCr(400{\AA})/Cr$ were fabricated as a function of Cr thickness by KF magnetron sputtering. The saturation magnetization, coercive force and squareness with annealing temperature for these films were investigated. The values of saturation magnetization of $SiO_2/CoNiCr/Cr$ thin films decreased as the thickness of Cr underlayer increased, whereas coercive force increased as the thickness of Cr underlayer increased. The value of Ms was 600 emu/cc and the maximum value of Hc was 550 Oe. Especially, the value of saturation magnetization was rapidly decreased $SiO_2/CoNiCr/Cr(1700{\AA})$ thin films as the annealing temperature increased And the coercive force increased as the annealing temperature increased When annealing temperature was $650^{\circ}C$, the Ms was reduced to 90 % of the as-deposited film. And the Hc was showed maximum 1600 Oe. It was thought that Cr diffusion into CoNiCr layer reduced the magnetic moment of CoKiCr layer. In addition. Hc might he increased due to grain growth perpendicular to the film plane.

• Proceedings of the Korean Magnestics Society Conference
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• 1996.05a
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• pp.48-49
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• 1996

• Proceedings of the Korean Magnestics Society Conference
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• 1994.03a
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• pp.84-85
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• 1994

• 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.

• Journal of the Korean Vacuum Society
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• v.2 no.2
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• pp.152-160
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• 1993

In this study, we have investigated the influence of sputtering conditions (Ar pressure input powers, substrates) on coercivity and microstructures of GdFe, Co, CoCr thin films produced by the method of DC magnetron sputtering. In GdFe films, we have observed that the Gd atomic ratio was decreased with the deposition rate, and deposition rate decreased with the pressure of Ar gas and the increased linearly with input power. It was also observed that the coercivity of thin films was increased with input power. In Co films, we have investigated the deposition was increased and the Co thin film became finer structure with the increase in the input power, was increased and the Co thin film became finer structure with the increase in the input power, and the deposition rate was decreased with the pressure of Ar gas. In CoCr films, we have investigated the effects of substrates on the coercivity $(H_c)$ and the microstructure. We have found that the substrates plays a crucial role in the microstructure and the coercivity $(H_c)$.