• 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.

• Electrical & Electronic Materials
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• v.11 no.10
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• pp.72-77
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• 1998

The effects of Al micro-bumps on the magnetic properties of CoCr(Pt)Ta/Cr films deposited on glass substrates were investigated. The coercivity increased and the coercivity squareness decreased by incorporating Cr/Al underlayers. The cause of the coercivity increase is attributed to the reduction of Co(0002) texture, the increase of magnetic isolation of CoCr(Pt)/Ta grains, and the refinement of CoCr(Pt)/Ta grains deposited on Cr/Al underlayers. The effects of an Al overlayer on the magnetic properties of CoCr(Pt)Ta/Cr films were also studied. The decrease of coercivity squareness is ascribed to the magnetic isolation of CoCr(Pt)Ta grains.

• 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.

• Journal of Magnetics
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• v.15 no.1
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• pp.12-16
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• 2010

Combined study of in-situ stress measurements and atomic force microscopy (AFM) revealed drastic stress relaxation in the CoCrPt and PS(styrene)-PVP(vinyl pyridine) polymer hybrid structure that was closely related to the growth structure of the film. We have observed not only no large initial growth stress at the initial stages of film growth but also twice smaller stress in magnitude with opposite sign in the CoCrPt/PS-PVP/Si sample. The microstructural studies using AFM at the various film growth stages revealed that the film growth structure plays an important role in the stress relaxation mechanism of CoCrPt films on a corrugated polymer surface.

• Journal of Magnetics
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• v.7 no.3
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• pp.106-114
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• 2002

To reduce the grain size and the media noise in a typical CrMo/CoCrPtB longitudinal media, a sputtering process which includes the exposure of oxygen onto the surface of CrW$_x$ (x=0, 25, 50, 75, 100 at.%) and CrTi$_{15}$ seedlayers with the thickness of 0.5 nm have been utilized. The main results are: (1) the media grain size and the media noise are reduced when using CrW$_x$ (x=0, 25, 50 at.%) seedlayers, and not reduced when using CrTils or CrW$_x$ (x=75, 100 at.%) seedlayers, (2) AES and RHEED results suggest that W seedlayer, which has the highest melting point, forms layer-like film with very small and dense island grain, due to its high free surface energy and low mobility. On the other hand, CrW$_{50}$ and Cr seedlayers, which have lower melting point than W seedlayer, form island film, (3) to effectively reduce the media grain size and improve the media signal to noise ratio, it is essential to utilize a very thin Cr-based seedlayer with high affinity for oxygen and which forms island-like structure, such as CrW$_{50}$ seedlayer.

• Electrical & Electronic Materials
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• v.8 no.4
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• pp.464-471
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• 1995

메그네트론 스퍼터링으로 제작한 고밀도 다층박막($Co_75{{Pt_12}{Cr_13}}$합금) 디스크를 투과전자현미경을 이용해 단면 및 평면의 미세조직의 조사 혹은 미소부위 성분분석을 할 경우, 선행되어야하는 시편준비 경로와 각 단계별 구체적방법 및 그 효과를 연구하였다. Ion밀링시간이 증가함에 따라 시료가 얇게 되는과정에서 스퍼터링된 물질이 관찰될 시편부위의 다른 표면에 증착되므로써 미세조직의 선명도를 해칠 수 있고, 이로인한 해석상의 오류가능성이 시사되었다. 또한, 자기박막 디스크와 같이 다층으로 구성된 단면분석용 시료에서는 서로 맞붙인 실리콘 단결정 접착면을 따라 밀링속도가 선택적으로 커서 우선축이 생김으로써 양질의 시편을 얻기 어려운 문제점이 제기되었다. 이같은 문제를 포함한 전자현미경 시료준비과정에서 생길 수 있는 문제를 해결할 수 있는 실마리와 이를 이용해 수행한 전자현미경 분석결과 및 효과적인 시편준비방법이 본 논문에서 언급되었다.

• Journal of the Korean Magnetics Society
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• v.27 no.2
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• pp.41-48
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• 2017

Recent study shows that ordered alloy of $L1_2$ $XPt_3$ (M = V, Cr, Mn, Co, and Fe) exhibits various magnetic phases such as ferromagnetic-to-antiferromagnetic transition at the $MnPt_3$ surface. Moreover, it has been argued that $CrPt_3$, in particular, possess large magnetocrystalline anisotropy and Kerr rotation with possible violation of Hund's rule. As such, we extend our work to thickness dependence of the magnetic structure of $CrPt_3$ thin film using density functional theory. Magnetic ground state of the bulk $CrPt_3$ turns out to be ferromagnetic (FM), where other magnetic phases such as A-type (A-AF), C-type (C-AF), and G-type antiferromagnetic (G-AF) state have higher total energies than FM by 0.517, 0.591, and 0.183 eV, respectively, and magnetic moments of Cr in bulk are respectively 2.807 (FM), 2.805 (A-AF), 2.794 (C-AF) and $2.869_{{\mu}_B}$ (G-AF). We extend our study to $CrPt_3$(001) thin films with CrPt-and Pt-termination. The thickness and surface-termination dependences of magnetism are investigated for 3-9 monolayers (ML), where different magnetic phases from bulk emerge: C-AF for CrPt-terminated 3 ML and G-AF for Pt-terminated 5 ML have energy difference relative to FM by 8 and 54 meV, respectively. Furthermore, thickness- and surface-termination-dependent magnetocrystalline anisotropies of the $CrPt_3$(001) films are discussed.

• Proceedings of the Korean Magnestics Society Conference
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• 2003.12a
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• pp.118-118
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• 2003