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.

일정 벽면 온도 조건에서 이성분 혼합물의 핵비등시 벽면 열유속 거동

배성원,이한춘,김무환,Bae, Sung-Won,Lee, Han-Choon,Kim, Moo-Hwan 대한기계학회 2000 大韓機械學會論文集B Vol.24 No.9

The objective of this work is to measure space and time resolved wall heat fluxes during nucleate pool boiling of R113/R11 mixtures using a microscale heater array in conjunction with a high speed CCD. The microscale heater array is constructed using VLSI techniques, and consists of 96 serpentine platinum resistance heaters on a transparent quartz substrate. Electronic feedback circuits are used to keep the temperature of each heater at a specified temperature and the variation in heating power required to keep the temperature constant is measured. Heat flux data around an isolated bubble are obtained with triggered CCD images. CCD images are obtained at a rate of 1000frames/second. The heat transfer variation vs. time on the heaters directly around the nucleation site is plotted and correlated with images of the bubble obtainedby using the high speed CCD. For both of the mixture(R11/R113) and pure system(pure R11, pure R113), the wall heat fluxes are presented and compared to find out the qualitative difference between pure and binary mixture nucleate boiling.

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.

루버핀 형상에 따른 공조기용 열교환기의 전열 및 착상성능

김주혁(Ju Hyok Kim),이한춘(Han Choon Lee),이상열(Sang Yeul Lee),김홍성(Hong Sung Kim),오세기(Sai Kee Oh) 대한설비공학회 2013 대한설비공학회 학술발표대회논문집 Vol.2013 No.6

In order to develop the heat exchanger for outdoor unit with excellent heating and frosting performance, the heat exchanger with various shape of louver fin was investigated experimentally. The conditions to affect the heat exchanger performance such as outer diameter of tube, tube pitch, fin number were fixed. The same heat exchanging rate, the 25% reduction of air pressure drop, and 71% delay of frosting time were achieved by using the louver fin designed with small louvers placed only near the tube.

포화상태 풀비등시 단일기포의 성장에 관한 연구

김정배(Jeongbae Kim),이한춘(Han Choon Lee),오병도(Byung Do Oh),김무환(Moo Hwan Kim) 대한기계학회 2004 대한기계학회 춘추학술대회 Vol.2004 No.4

Nucleate boiling experiments with constant wall temperature of heating surface were performed using R113 for almost saturated pool boiling conditions. A microscale heater array and Wheatstone bridge circuits were used to maintain a constant wall temperature condition and to measure the heat flow rate with high temporal and spatial resolutions. Bubble images during the bubble growth were taken as 5000 frames a sec using a high-speed CCD camera synchronized with the heat flow rate measurements. The geometry of the bubble during growth time could be obtained from the captured bubble images. The bubble growth behavior was analyzed using the new dimensionless parameters for each growth regions to permit comparisons with previous results at the same scale. We found that the new dimensionless parameters can describe the whole growth region as initial and later respectively. The comparisons showed good agreement in the initial and thermal growth regions. The required heat flow rate for the volume change of the observed bubble was estimated to be larger than the instantaneous heat flow rate measured at the wall. Heat, which is different from the instantaneous heat supplied through the heating wall, can be estimated as being transferred through the interface between bubble and liquid even with saturated pool conditions. This phenomenon under a saturated pool condition needs to be analyzed and the data from this study can supply the good experimental data with the precise boundary condition (constant wall temperature).

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.

공조기용 Corrugate Fin-Tube 열교환기의 냉난방 및 착상성능

김주혁(Ju Hyok Kim),김홍성(Hong Sung Kim),이한춘(Han Choon Lee),사용철(Yong Cheol Sa),오세기(Sai Kee Oh) 대한설비공학회 2010 대한설비공학회 학술발표대회논문집 Vol.2010 No.6

An outdoor heat exchanger of heat pump is used as an evaporator during heating operations and frost on its surface can grow at low outdoor temperatures. Frost increases the thermal resistance and the air-side pressure drop of evaporators, which decrease system heating performance. In this study, the evaporation, condensation and frosting performance of corrugate fin having an uniform air velocity and heat transfer is examined experimentally. In addition, the heat pump performance with the corrugate fin heat exchanger is compared with the louver fin heat exchanger. Heating capacity and COP of heat pump using corrugate fin increase by 36% and 19%, respectively.

스탠드 에어컨 실내기용 마이크로채널 증발기 분지 설계 기술

유상훈(Sang Hoon Yoon),김주혁(Ju Hyok Kim),이한춘(Han Choon Lee),장세동(Se Dong Chang) 대한기계학회 2016 대한기계학회 춘추학술대회 Vol.2016 No.4