• Journal of the Korean Magnetics Society
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• v.2 no.1
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• pp.61-68
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• 1992

Structural, magnetic and magneto-optical(1.0~3.2eV) properties of rare earth (Ce, Pr, Eu), transition metal(Ni, Co), and Al substituted polycrystalline Ba ferrite films grown by rf sputtering have been investigated. TEM studies revealed that crystal grains in the films were reduced in size from several hundred nm to the order of 1 nm with the decrease of rf power density during sputtering. By substituting Al, square hysteresis loops have successfully been obtained. It has been found that Niions strongly enhances Faraday rotation of the films in the visible range. It has been confirmed that Co ions also strongly enhances Faraday rotation of the films in the near infrared. En- hancement in Faraday rotation by Ce, Pr, and Eu ions has not been observed. The origin of the enhancement in magnetic and magneto-optical properties of the films is discussed.

• Journal of the Korean Magnetics Society
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• v.4 no.4
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• pp.319-325
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• 1994

Permalloy films were deposited by an RF magnetron sputtering method using several different targets which had been cold-rolled and annealed at various temperatures to give different microstructure and texture. The grain refinement occurs at high temperature annealing due to recrystallization and subsequently the initial (110) target texture transforms to the random texture. The coercive forces of thin films fabricated using targets which are not recrystallized are below 0.2 Oe in the AI pressure range of 1~5 mTorr and the lowest coercive force achieved is 0.07 Oe. The low value of coercive force, 0.25 Oe, is only obtained at the sputtering conditions of 400 W and 1 mTorr, and 300 W and 5 mTorr when recrystallized targets are used. The internal stress changes from compressive to tensile as the Ar pressure increases, the stress-free being at 5 mTorr. The changes of coercive force and permeability can be well interpreted by the differences from the composition and the internal stress.

• Journal of the Korean Magnetics Society
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• v.10 no.2
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• pp.62-66
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• 2000

Annealing cycle number and nonmagnetic layer thickness dependences of interlayer coupling field ( $H_{inf}$ ) and coercivity ( $H_{cf}$ ) of free magnetic layer on NiMn alloy-spin valve films (SVF) were investigated. The SVF is Glass (7059)/N $i_{81}$F $e_{l9}$(70 $\AA$)/Co(10 $\AA$)/Cu(t $\AA$)/Co(15 $\AA$)N $i_{81}$$Fe_{19}$(35 $\AA$)/N $i_{25}$M $n_{75}$(250 $\AA$)Ta(50 $\AA$) films, it were fabricated using the dc sputtering method at different pinning layer thickness and nonmagnetic spacer thickness (Cu thickness; 30 $\AA$, 35 $\AA$, 40 $\AA$) of NiMn alloy with 25 at.%. Ni In case that Cu thickness of SVF is 35 $\AA$ and peak exchange coupling field ( $H_{ex}$) was 620 Oe, while coercivity $H_{c}$ = 280 Oe and MR ratio showed 2.5%. As for $H_{inf}$ and $H_{cf}$ , every SVF increased up to the stabilized values with the increase of annealing cycle number 15, which were $H_{inf}$ of 120 Oe and $H_{cf}$ of 75 Oe. The increase of $H_{cf}$ with the annealing cycle number seems to be caused by the effective reduction of Cu layer thickness due to the increase of interfacial mixing of Cu layer and Co layer. In addition, the $H_{inf}$ and $H_{cf}$ dependences of free NiFe layer by the interfacial mixing effect were appeared the different aspects when Cu layer becomes more thinner and thicker than Cu layer thickness of 35 $\AA$, respectively.ively....

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.18 no.3
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• pp.276-283
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• 2005

Magnetic tunneling transistor (MTT) device using the amorphous n-type Si semiconductor film for base and collector consisting of the [CoFe/NiFe](free layer) and Si(top layer) multilayers was used to study the spin-dependent hot electron magnetocurrent (MC) and tunneling magnetoresistance (TMR) at room temperature. A large MC of 40.2 % was observed at the emitter-base bias voltage ( $V_{EB}$ ) of 0.62 V. The increasing emitter hot current and transfer ratio ( $I_{C}$/ $I_{E}$) as $V_{EB}$ are mainly due to a rapid increase of the number of conduction band states in the Si collector. However, above the $V_{EB}$ of 0.62 V, the rapid decrease of MC was observed in amorphous Si-based MTT because of hot electron spin-dependent elastic scattering across CoFe/Si interfaces.

• Journal of the Korean Magnetics Society
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• v.14 no.6
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• pp.236-239
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• 2004

We studied the specular spin valve (SSV) having the spin filter layer (SFL) in contact with the ultrathin free layer composed of Ta3/NiFe2/IrMn7/CoFel/(NOLl)/CoFe2/Cu1.8/CoFe( $t_{F}$)/Cu( $t_{SF}$ )/(NOL2)/Ta3.5 (in nm) by the magnetron sputtering system. For this antiferromagnetic I $r_{22}$M $n_{78}$-pinned spin filter specular spin valve (SFSSV) films, an optimal magnetoresistance (MR) ratio of 11.9% was obtained when both the free layer thickness ( $t_{F}$) and the SFL thickness ( $t_{SF}$ ) were 1.5 nm, and the MR ratio higher than 11% was maintained even when the $t_{F}$ was reduced to 1.0 nm. It was due to increase of specular electron by the nano-oxide layer (NOL) and of current shunting through the SFL. Moreover, the interlayer coupling field ( $H_{int}$) between free layer and pinned layer could be explained by considering the RKKY and magnetostatic coupling. The coercivity of the free layer ( $H_{cf}$ ) was significantly reduced as compared to the traditional spin valve (TSV), and was remained as low as 4 Oe when the $t_{F}$ varied from 1 nm to 4 urn. It was found that the SFL made it possible to reduce the free layer thickness and enhance the MR ratio without degrading the soft magnetic property of the free layer.

• Proceedings of the Korean Vacuum Society Conference
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• 2013.02a
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• pp.566-566
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• 2013

종래의 흑연 위주 연료전지 분리판에서 최근 고분자 전해질 막 연료전지가 높은 전력, 낮은 작동 온도로 자동차 산업에서 상당한 주목을 받고 있다. 분리판의 기술적 요구사항은 높은 전기 전도도, 높은 내식성, 가스 밀봉성, 경량성, 가공성, 저비용 등이다. 후보 물질로는 전기 전도성을 갖는 질화물계가 고려되고 있다. 기판으로는 스테인레스강이 가장 유력하며 Fe에 첨가된 Ni, Cr이 존재하므로 Cr 또는 CrN를 박막의 형태로 전자빔 증발법, 마그네트론 스퍼터링법으로 고속 증착하려는 시도가 있었다. 본 연구에서는, 스테인리스 강박(0.1 mm 이하)에 보호막으로 CrN을 선택하고 고속, 고품질증착을 위해서 새로운 방법인 스퍼터 승화법을 개발하였다. 박막의 품질을 개선할 수 있는 고밀도 유도 결합 플라즈마 영역 내에 Cr 소스를 직류 바이어스 함으로써 가열 및 스퍼터링이 일어나도록 하였다. 5 mTorr의 Ar 유도 결합 플라즈마를 2.4 MHz, 500 W로 유지하면서 직류 바이어스 전력을 30 W (900 V, 0.02 A) 인가하고, $N_2$의 유량을 0.5, 1.0, 1.5 SCCM로 변화를 주어 반응성 증착 공정의 결과로 얻어지는 CrN 박막의 특성을 분석하였다. N2의 유량이 증가할수록 $Cr_2N$이 감소하고, CrN이 증가하는 것을 확인하였다. 또한 부식성과 접촉저항을 측정하였다. 부식 전위는 N20 SCCM 보다 모두 상승하는 것을 확인하였고, $N_21$ SCCM에서 부식 전류 밀도가 2.097E-6 (at 0.6V) $A/cm^2$로 나타났다. 접촉저항 에서는 시료 당 3군데(top, center, bottom)를 측정하였다. 전기전도도 측면에서 가장 좋은 결과는 $N_21$ SCCM 일 때 $28.8m{\Omega}{\cdot}cm^2$의 접촉저항을 갖는 경우였다. 미국 에너지성의 기준은 부식 전류밀도 1.E-6 $A/cm^2$이하, 접촉 저항 $0.02{\Omega}m^2$이므로 매우 근접한 결과를 보이고 있다.

• Journal of the Korean Magnetics Society
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• v.17 no.1
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• pp.22-25
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• 2007

In this research, magnetic properties of spin valve structures using IrMn layers as antiferromagnetic were studied depending on the thickness of the pinned layer. The spin valve structure was Si substrate/$SiO_2(2,000\;{\AA})/Mo(17\;{\AA})NiFe(21\;{\AA})/CoFe(28\;{\AA})/Cu(22\;{\AA})/CoFe(18\;{\AA})/IrMn(t\;{\AA})/Ta(25\;{\AA})$. Also, Mo film was deposited on Si substrates and the thermal annealing effect was analyzed. The resistivity of the Mo film was increased as an annealing temperature was increased up to $600^{\circ}C$. The variations of MR ratio were related with magnetic exchange coupling field of the spin valve structures for various IrMn pinned layer thickness up to 130 ${\AA}$. MR ratio and $H_{ex}$ of spin valves was about 9.05% and 277.5 Oe when the thickness of the IrMn pinned layer was $32.5\;{\AA}(t=32.5\;{\AA})$. It was increased to 9.65% and 337.5 Oe for $t=65\;{\AA}$. For $t=97.5\;{\AA}$, the MR ratio and Hex decreased to 8.2% and 285 Oe, and further decrease was observed up to $t=130\;{\AA}$.

• 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 Electrochemical Society
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• v.11 no.4
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• pp.284-288
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• 2008

Sn-thin film as high capacitive anode for thin film lithium-ion battery was prepared by organic-electrolyte electroplating using Sn(II) acetate. Electrolytic solution including $Li^+$ and $Sn^{2+}$ had 3 reduction peaks at cyclic voltammogram. Current peak at $2.0{\sim}2.5\;V$ region correspond to the electroplating of Sn on Ni substrate. This potential value is lower than 2.91 V vs. $Li^+/Li^{\circ}$, of the standard reduction potential of $Sn^{2+}$ under aqueous media. It is the result of high overpotential caused by high resistive organic electrolytic solution and low $Sn^{2+}$ concentration. Physical and electrochemical properties were evaluated using by XRD, FE-SEM, cyclic voltammogram and galvanostatic charge-discharge test. Crystallinity of electroplated Sn-anode on a Ni substrate could be increased through heat treatment at $150^{\circ}C$ for 2 h. Cyclic voltammogram shows reversible electrochemical reaction of reduction(alloying) and oxidation(de-alloying) at 0.25 V and 0.75 V, respectively. Thickness of Sn-thin film, which was calculated based on electrochemical capacity, was $7.35{\mu}m$. And reversible capacity of this cell was $400{\mu}Ah/cm^2$.

• Journal of the Korean Magnetics Society
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• v.8 no.6
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• pp.357-361
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• 1998

For CoZr/Ag/CoCr trilayered films deposited by DC and FR magnetron sputtering method, ferromagentic resonance experiments have been used to investigate the dependence of the exchange coupling between CoZr and CoCr layers separated by Ag layer on the thickness of the Ag layer. The coupling strength K increases with increasing Ag thickness up to 10 $\AA$ with a maximum value of 748 Oe, but oscillates with increasing Ag thickness in the range from 20 to 100 $\AA$. The coupling strength is positive for all samples. Hence, it seems that the exchange coupling between CoZr and CoCr layers separated by Ag layer is ferromagnetic.