• Journal of the Korean Magnetics Society
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• v.2 no.1
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• pp.56-60
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• 1992

광자기 디스크의 자기 및 기록특성에 SiN 하지층이 미치는 영향에 대해서 연구하였다. PC기관에 4층구조막의 디스크를 DC 마그네트론 스퍼터링에 의해 성막하였으며 스퍼터링 압력이 증가함에 따라 SiN 박막의 표면이 거칠어 지고 주상형성장이 현저하게 나타났다. SiN 하지층의 비세조직의 변화는 자기기록막의 보자력, 수직이방성 등에는 영향을 미치지 않았지만 지구의 형 성과정은 SiN 하지층의 조직에 따라 민감하게 변화하였다. SiN 하지층이 Porous 할수록 광자기 디스크의 기록이 이루어 지는 임계파우워 값이 작고, 또한 자구의 형성이 이루어 지는 임계외자 계의 크기도 넓은 범위에서 나타났다. 광자기 디스크의 기록특성을 증대시키기 위해서는 자기기 록막의 성능과는 관계없이 치밀하고 표면이 평할한 SiN 하지층을 증착하는 것이 필수적임을 관 찰하였다.

• Journal of the Korean Magnetics Society
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• v.13 no.3
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• pp.91-96
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• 2003

Cross-geometrical Cr/Co/Al-Ox/Co/Ni-Fe tunnel junctions were fabricated by magnetron sputtering. To form an insulating layer, The Al layer was oxidized in an atmosphere of oxygen-argon mixture at low power after deposition. To enhance the coercivity of the bottom Co layer, The Cr seed layer was deposited on the glass and it led to increase in coercivity. The coercivity increase is due to the increase of roughness through the Cr thickness. In over oxidation time, the oxidation of Co bottom layer and flat interface of insulator can increase the bottom Co coercivity. But TMR ratio gradually decrease. TMR ratio is relevant with Cr thickness, insulator thickness, and oxidation time. The maximum TMR ratio was 14% at room temperature and the TMR ratio was decreased to half at 0.51 V.

• Journal of the Korean Magnetics Society
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• v.3 no.4
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• pp.314-319
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• 1993

The Effects of additional element X (X = Si, Mo, Cu, Gd) on magnetic properties and microstructure of Co-1Zat%Cr-Zat%Ta/Cr-X magnetic thin film were investigated. The thickness changes of Cr-X underlayer and CoCrTa magnetic layer were in the range of $1000~2000\AA$ and $200~800\AA$. respectively. Substrate temperatures were controlled from $100^{\circ}C$ to $200^{\circ}C$. Increase of coercivity by about 100~200 Oe was observed in CoCrTa/Cr-X thin films compared to those without additional X element. Cu was the most effective additional element for increasing coercivity. CoCrTa/Cr-Cu thin film shows relatively high coercivity in $1500\AA$ underlayer thickness and $600\AA$ magnetic layer thickness.

• Journal of the Korean Vacuum Society
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• v.21 no.5
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• pp.233-241
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• 2012

We have deposited the bilayer consisted of the underlayer and the overlayer by using DC magnetron sputter on Single crystal MgO (001) substrate. This bilayer was fabricated at fixed annealing temperature and time. We have controlled agglomeration effect by changing of the bilayer thickness. Finally, we have made the self-organization and nano-structured film. In this processing, we have made nano-dot which consists of the underlayer and the overlayer, unlike the existing method called the agglomeration effect in the single layer. The underlayer has deposited using Ti, Cr and Co. And the overlayer has deposited with Ag. Through the analysis of Atomic force microscopy (AFM), the microstructure of underlayer is observed by AFM to confirm the formation of nano-dot. As the nano-dot through above processing, we have found that the nano-dot has the different shape. As a result, when we manufactured nano-dot through the agglomeration effect of bi-layer, the best matching material is Ti for underlayer. And also, we have found that MgO/Ti/Ag samples have been grown expitaxially toward the direction of MgO (001) by X-ray Diffraction analysis.

• Journal of the Korean Magnetics Society
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• v.15 no.4
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• pp.226-230
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• 2005

In this research, magnetic properties and annealing effects of the spin valve structures were investigated, which have Ta underlayer deposited with Ar and $N_2$ gas mixture. Also, TaN underlayer as a diffusion barrier and the substrate were investigated. The structure of the spin valve was Si($SiO_2$)/Ta(TaN)/NiFe/CoFe/Cu/CoFe/FeMn/Ta. Deposition rate was decreased and resistivity and roughness of the TaN films were increased as the $N_2$ gas flow was increased. The XRD results after high temperature annealing showed that Silicides were created in Si/Ta layer, but not in Si/TaN layer. Magnetoresistance ratio (MR) and exchange coupling field ($H_{ex}$) were decreased when the $N_2$ gas flow was increased over 4.0 sccm. The MR of the spin valves with Ta and TaN films deposited with up to 4.0 sccm of $N_2$ gas flow was increased about $0.5\%$ until the annealing temperature of up to $200^{\circ}C$ and then, decreased. TaN film deposited with 8.0 sccm of $N_2$ gas flow showed twice the adhesion of the Ta film. The above results indicate that with 3.0 sccm of $N_2$ gas flow during the Ta underlayer deposition, the magnetic properties of the spin valves are maintained, while the underlayer may be used as a diffusion barrier and the adhesion between the Si substrate and the underlayer is increased.

• 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 Magnetics Society
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• v.18 no.3
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• pp.94-97
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• 2008

We investigated how the magnetic anisotropy in $[Co(2\;{\AA})/Ni(8\;{\AA})]{\times}N$ multilayers varied with the type and thickness of an underlayer. The magnetic measurements clearly showed that the perpendicular magnetic anisotropy could be developed in the Co/Ni multilayer by adopting an underlayer with [111] texture. The coercivity of the Co/Ni multilayer increased from 99 Oe to 430 Oe as the thickness of an Au underlayer increased from $50\;{\AA}$ to $500\;{\AA}$. The increase in coercivity is ascribed to the development of the stronger [111] texture in the Co/Ni multilayer as an Au underlayer gets thicker.

• Journal of the Korean Magnetics Society
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• v.16 no.5
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• pp.240-244
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• 2006

In this paper, magnetic properties and annealing behavior of spin valve structures using Mo(MoN) layers as underlayers were studied varying the thickness of the underlayers. The spin valve structure was consisted of Si substrate/$SiO_2(2,000{\AA})/Mo(MoN)(t{\AA})/NiFe(21\;{\AA})/CoFe(28\;{\AA})/Cu(22\;{\AA})/CoFe(18\;{\AA})/IrMn(65\;{\AA})/Ta(25\;{\AA})$. Also, MoN films were deposited on Si substrates and their thermal annealing behavior was analyzed. The resistivity of the MoN film increased as the $N_2$ gas flow rate was increased. After annealing at $600^{\circ}C$, XRD results did not show peaks of silicides. XPS results indicated MoN film deposited with 5 sccm of $N_2$ gas flow rate was more stable than the film deposited with 1 sccm of $N_2$ gas flow rate. The variations of MR ratio and magnetic exchange coupling fold were small for the spin valve structures using Mo(MoN) underlayers up to thickness of45 ${\AA}$. MR ratio of spin valves using MoN underlayers deposited with various $N_2$ gas flow rate was about 7.0% at RT and increased to about 7.5% after annealing at $220^{\circ}C$. Upon annealing at $300^{\circ}C$, the MR ratio decreased to about 3.5%. Variation of $N_2$ gas flow rate up to 5 sccm did not change the MR ratio and $H_{ex}$ appreciably.

• Journal of the Korean Magnetics Society
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• v.9 no.4
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• pp.203-209
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• 1999

Effects of Mo and Si addition in Cr underlayer on magnetic properties of CoCrTa/CrMo and CoCrTa/Si thin films media were investigated. Thin films were prepared with DC magnetron sputtering system. The thickness of CoCrTa magnetic layer and Cr underlayer were fixed at 300 $\AA$ and 700 $\AA$, respectively. The substrate heating temperature was kept constant at 26$0^{\circ}C$ for both magnetic layer and underlayer preparation. The coercivity increase of CoCrTa film was realized due to Mo addition in Cr underlayer. Si addition made a small decrease in coercivity. Coercivity increase seems to be attributed by the improvement of preferred orientation of Cr(200) plane. It is found that lattice fit between Cr(200) and CoCrTa(1120) of CrMo underlayer is better than that of CrSi underlayer. This small misfit may also contribute coercivity increase.

• Journal of the Korean Magnetics Society
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• v.17 no.2
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• pp.95-98
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• 2007

In this paper, the magnetic properties and the annealing behavior of spin valve structures with Mo(MoN) underlayers were studied for various underlayer thickness. The spin valve structure was Si substrate/Mo(MoN)$(t{\AA})/NiFe(21{\AA})/CoFe(28{\AA})/Cu(22{\AA})/CoFe(18{\AA})/IrMn(65{\AA})/Ta(25 {\AA})$. Mo and MoN films were deposited on Si substrates and their thermal annealing behavior was analyzed. The deposition rate of the MoN thin film was decreased and tile resistivity of the MoN thin films were increased as the $N_2$ gas flow was increased. The variations of MR ratio and magnetic exchange coupling field of spin valve structure were smaller with MoN underlayers than that with Mo underlayers up to thickness of $51{\AA}$. MR ratio of spin valves with Mo underlayers was 2.86% at room temperature and increased up to 2.91 % after annealing at $200^{\circ}C$. Upon annealing at $300^{\circ}C$, the MR ratio decreased about 2.16%. The MR ratio of spin valves structure with MoN underlayers for $N_2$ gas flow 1 sccm was 5.27% at room temperature and increased up to 5.56% after annealing at $200^{\circ}C$. Upon annealing at $300^{\circ}C$, the MR ratio decreased about 4.9%.