비정질 Fe₇₇Si₁₀B₁₃ 합금의 비저항 및 Hall 효과

김택기(Taik Kee Kim),임영언(Yeong Eon Ihm),어봉환(Bong Whan Lau) 대한공업교육학회 1982 대한공업교육학회지 Vol.7 No.1

The electrical resistivity and Hall effect of amorphous Fe₇₇Si₁₀B₁₃ have been investigated in the temperature range of 300-1200˚K and the applied magnetic fields up to 17 KOe. It turned out as follows: 1) The electrical resistivity at room temperature was 1.2 X 10^(-4) Ω·㎝ and the temperature coefficient of resistivity was 1.77 × 10^-4 ˚K^-1. 2) Curie temperature and crystallization temperature were 725˚K and 803˚K. 3) The ordinary Hall coefficient, the spontaneous Hall coefficient, and the spontaneous Hall conductivity were 44.5 x 10^-12 Ω·㎝/Oe, 475 X 10^-12 Ω·㎝/Oe and 4.9 (Ω·㎝)^-1, respectively.

비정질 Fe₈₀Si_xB_20-x 합금의 결정화 과정의 속도론적 연구

김택기(Taik Kee Kim),금은섭(Eun Seob Keum),노봉환(Bong Wan Lau) 대한공업교육학회 1984 대한공업교육학회지 Vol.9 No.1

In order to study the thermal stability in amorphous Fe_(80)Si_XB_(20-X) alloys, which have good soft magnetic properties, the structure analysis has been carried out with DTA and X-ray diffractometer and the activation energy for transformation has been investigated with DSC. The results are as follows; 1) The crystallization in amorphous Fe_(80)Si_XB_(20-X) alloys proceeds in 2-stage, amorphous →α·Fe →α·Fe + Fe₂B, in all range of Si concentration. 2) The temperature of the first transformation decreases with Si concentration, but that of the second transformation increases with Si concentration slightly. 3) The activation energies in both stages decrease with Si concentration in amorphous Fe_(80)Si_XB_(20-X) alloys.

고등학교 기술 교과의 프로젝트 학습을 위한 자기 임피던스 측정 장치 제작

김용국(Yong Kook Kim),김택기(Taik Kee Kim),이희복(Hee Bok Lee) 대한공업교육학회 1999 대한공업교육학회지 Vol.24 No.2

A simple apparatus for the Magneto-impedance measurement was made with gaussmeter, solenoid, signal generator and power supply. The apparatus can be used for the subject of advanced materials as a teaching materials for open education of the technology subject in high school. Students can learn various concepts such as advanced soft magnetic materials, magnetic sensor, impedance, annealing, etc. by using the magneto-impedance measurement system.

비정질 금속 Fe78B₁₃Si9의 주파수에 따른 자기 임피던스 효과

김용국(Yong-Kook Kim),김택기(Taik-Kee Kim),이희복(Heebok Lee) 한국자기학회 1997 韓國磁氣學會誌 Vol.7 No.1

The frequency dependence of magnetoimpedance (MI) effect in amorphous Fe_(78)B₁₃Si_9 alloy has been obtained. Magnetoimpedance (MI) effect is a high-frequency phenomenon, which describes the changes of impedance in any ferromagnetic sample, when a magnetic field is applied on it. MIR (Magnetoimpedance ratios) is defined as Δ Z/Z ≡ [Z(0)/Z(Hs)]-1 where Hs is the saturating field along the long side of the sample. The MIR of the samples annealed in vacuum has been decreased normally except that the sample annealed at 5㎒ has been reached as much as 58%.

電子線으로 照射된 低密度 Polyethylene의 電氣傳導度와 溫度特性

李宗珪(Jong Kyoo Lee),金永銓(Young Jurn Kim),金澤基(Taik Kee Kim) 호서대학교 중앙도서관 1993 호서대학교 논문집 Vol.1 No.-

Conductivity in polyethylene has been investigated as the applied electric fields between 1.1×10⁴ and 2.5×10⁵ V/cm and temperature from 20°C to 105°C. The comparative analysis of the theory with the experiment results were tried on the assumption that the current is composed of eletrons injected into sample which contains space charge over the Schottky barrier. From the results a rough estimate was made of the density of traps in irradiated polyethylene and the activation energy, which could be calculated from the temperature dependence of electrical conductivities of polyethylene irradiated with 10⁸rad electron beam, were obtained 0.28 eV and 1.06eV,

NiFe / Co / Al₂O₃ / Co / IrMn 접합의 터널링 자기저항효과

홍성민(Seong-Min Hong),이한춘(Han-Choon Lee),김택기(Taik-Kee Kim),N. Tezuka(N. Tezuka),T. Miyazaki(T. Miyazaki) 한국자기학회 1999 韓國磁氣學會誌 Vol.9 No.6

IrMn을 반강자성체로 사용하고 순수한 Al을 자연산화 시켜서 제작한 Al2O3를 절연층으로 사용한 spin-valve 형태의 NiFe/Co/Al₂O₃/Co/IrMn 터널링 접합의 자기저항효과를 조사하였다. IrMn의 두께가 약 100Å이상일 경우 강자성체와의 교환상호작용이 발생하기 때문에 NiFe(183Å)/Co(17Å)/Al-oxide(16Å)/Co(100Å)/IrMn(100Å) 터널링 접합에서 자기저항효과가 관찰되며 TMR비(%)는 ±20 Oe의 인가자장에서 10 %이상의 값을 갖는다. 하부 자성층인 NiFe/Co의 길이방향으로 수행한 자장 중 열처리에 의해 저항은 다소 감소하고 TMR비(%)는 열처리온도에 따라 증가하여 200 ℃에서 23%의 최대값을 갖는다. 자성층의 폭을 변화시켜 접합면적을 달리한 시료의 TMR비(%)는 접합면적이 증가할수록 증가하고 저항은 감소한다. NiFc/Co/Al₂O₃/Co/IrMn tunneling junctions were grown on (100)Si wafer and their spin-valve tunneling magnetoresistance (TMR) was studied. The tunneling junctions were grown by using a 5-gun RF/DC magnetron sputter. Al2O3 barrier layer was formed by exposing Al layer to oxygen atmosphere at 60℃ for 72 hours. Strong exchange coupling interaction is observed between the ferromagnetic Co and the anti ferromagnetic IrMn of Co/IrMn bilayer when IrMn is 100 Å thick. NiFc(183 Å)/Co(17 Å)/Al-oxide(16 Å)/Co(100 Å)/IrMn(100 Å) tunneling junction shows best TMR ratio of about 10% in the applied magnetic field range of ±20 Oe. The TMR ratio is improved about 23% and electrical resistance is decreased about 34% when annealed at 200℃ for I hour in magnetic field of 330 Oe, parallel to the bottom electrode. With increasing the active area of junction the TMR ratio increases while electrical resistance decreases.

FeN / Co / Cu / Co계 spin - valve형 다층막의 자기저항 특성

이한춘(Han-choon Lee),송민석(Min-seok Song),윤성호(Seong-ho Youn),김택기(Taik-kee Kim) 한국자기학회 2000 韓國磁氣學會誌 Vol.10 No.5

The magnetoresistance characteristics of FeN/Co/Cu/Co and FeN/Co/Cu/Co/Cu/Co/FeN multilayers using ferromagnetic iron-nitrides (FeN) has been studied. The microstructure of FeN film is the mixed α-Fe and ε-Fe₃N phase on the condition that the flow rate of N₂ gas is over 0.4 sccm. The magnetoresistance effect is observed because of shape magnetic anisotropy induced by needle-shaped ε-Fe₃N phase. This magnetoresistance effect changes, because the degree that the shape magnetic anisotropy adheres to the adjacent Co pinned layer is varied according to the flow rate of N₂ gas and the thickness of FeN film. The best magnetoresistance effect is obtained on the condition that the thickness of Co free layer is 70 Å and the maximum MR ratio(%) value of 3.2 % shows in the FeN(250 Å)/Co(70 Å)/Cu(25 Å)/Co(70 Å)/Cu(25 Å)/ Co(70 Å)/ FeN(250 Å) mutilayer film which is fabricated at the N₂ gas flow rate of 0.5 sccm and the FeN film thickness of 250 Å. Four steps are observed in the magnetoresistance curve owing to this difference of coercive force, because respective magnetic layers in the multilayer possess different coercive forces. These effects observed in these mutilayer films can be expected to application to the memory device the same MRAM as can carry out simultaneously four signals.

NiFe / Co / Al₂O₃ / Co / IrMn 접합의 터널링 자기저항효과

홍성민(Seong-Min Hong),이한춘(Han-Choon Lee),김택기(Taik-Kee Kim),N. Tezuka(N. Tezuka),T. Miyazaki(T. Miyazaki) 한국자기학회 1999 韓國磁氣學會誌 Vol.9 No.6

IrMn을 반강자성체로 사용하고 순수한 Al을 자연산화 시켜서 제작한 Al2O3를 절연층으로 사용한 spin-valve 형태의 NiFe/Co/Al₂O₃/Co/IrMn 터널링 접합의 자기저항효과를 조사하였다. IrMn의 두께가 약 100Å이상일 경우 강자성체와의 교환상호작용이 발생하기 때문에 NiFe(183Å)/Co(17Å)/Al-oxide(16Å)/Co(100Å)/IrMn(100Å) 터널링 접합에서 자기저항효과가 관찰되며 TMR비(%)는 ±20 Oe의 인가자장에서 10 %이상의 값을 갖는다. 하부 자성층인 NiFe/Co의 길이방향으로 수행한 자장 중 열처리에 의해 저항은 다소 감소하고 TMR비(%)는 열처리온도에 따라 증가하여 200 ℃에서 23%의 최대값을 갖는다. 자성층의 폭을 변화시켜 접합면적을 달리한 시료의 TMR비(%)는 접합면적이 증가할수록 증가하고 저항은 감소한다. NiFc/Co/Al₂O₃/Co/IrMn tunneling junctions were grown on (100)Si wafer and their spin-valve tunneling magnetoresistance (TMR) was studied. The tunneling junctions were grown by using a 5-gun RF/DC magnetron sputter. Al2O3 barrier layer was formed by exposing Al layer to oxygen atmosphere at 60℃ for 72 hours. Strong exchange coupling interaction is observed between the ferromagnetic Co and the anti ferromagnetic IrMn of Co/IrMn bilayer when IrMn is 100 Å thick. NiFc(183 Å)/Co(17 Å)/Al-oxide(16 Å)/Co(100 Å)/IrMn(100 Å) tunneling junction shows best TMR ratio of about 10% in the applied magnetic field range of ±20 Oe. The TMR ratio is improved about 23% and electrical resistance is decreased about 34% when annealed at 200℃ for I hour in magnetic field of 330 Oe, parallel to the bottom electrode. With increasing the active area of junction the TMR ratio increases while electrical resistance decreases.

자장열처리가 비정질 Fe80-xCoxSi6B14 합금의 자기적 성질에 미치는 영향

김택기,조용수,김기환 대한금속재료학회(대한금속학회) 1991 대한금속·재료학회지 Vol.29 No.6

Amorphous Fe_(80-x)Co_xSi_6B_(14)(10≤X≤70) alloys were annealed below their Curie temperatures in AC magnetic field in order to improve soft magnetic properties. Magnetization measurements were made as a function of applied AC magnetic field and annealing temperature and time. Magnetic measurement results clearly demonstrated that some beneficial effects can be provided by applying AC field during annealing, in improvement of the soft magnetic properties : a significant decrease both in coercive and in AC Power loss, and a tendency toward a square shape of hysteresis loop were observed in the our present study. The optimum experimental condition to obtain best magnetic properties for the amorphous Fe_(80-x)Co_xSi_6B_(14) alloys was determined to be AC field annealing treatment at 380℃ for 30 min with H_a≥30 Oe.

비정질 Fe80-xCoxSi6B14 합금의 자부

김택기,황인엽,조용수 대한금속재료학회(대한금속학회) 1989 대한금속·재료학회지 Vol.27 No.12

Magnetostriction of soft magnetic Fe_(80-x)Co_xSi_6B_(14)(10≤X≤78) amorphous alloy was investigated by using a small-angle magnetization rotation apparatus. Rapid quenching technique with using single roller was employed to prepare the amorphous ribbons. Saturation magnetizaion constant, λs, determined for alloys with various compositions. The magnetostriction reaches 22.2 ×10^(-6) for X= 10 and decreases with increasing Co content. The magnetostriction reaches zero at around X= 74.5 and is -2.60 ×10^(-6) at X=78. This result was compared with the magnetostriction of Fe-Co alloy. Metalloids do not affect the zero-magnetostriction of the amorphous.