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스퍼터링 조건에 따른 Co 박막의 증착속도 및 미세구조의 변화
백주열,박창만,최영근,이기암,황도근 단국대학교 신소재기술연구소 1992 신소재 Vol.2 No.-
DC 마그네트론 스퍼터링법으로 제조된 코발트 박막에 대해 증착속도 및 미세구조에 미치는 스퍼터링조건의 영향을 조사하였다. 증착속도는 투입전력이 커질수록 증가하였으며, 아르곤 압력이 커질수록 감소하였는데, 이는 투입전력의 증가로 인한 타게트 표면의 이온전류 밀도의 상승과 Ar 압력증가에 따른 비산효과의 증대로 인한 타게트 표면의 이온 전류 밀도의 감소로 고찰되었다. 투입전력이 커질수록 결정립의 크기가 감소하였으며, 투입 전력에 관계없이 특정한 면이 발달하지 않는 비정실 구조를 나타내었다. Ar 압력에 관계없이 비정질 구조를 나타내었다. We have investigated the influence of sputtering condition on deposition rate and microstructure of Co thin film produced by the method of DC Magnetron Sputtering. Deposition rate increased with the input power due to the rise in ionic current density on the surface of target, and decreased with the pressure of Ar gas due to the decrement of ionic current density by the effect of diffusion. Microstructure of the Co thin film became a finer structure with the increase in the input power, and showed amorphous irrespective of the charge of the input power and the pressure of Ar gas.
Frequency Effect on Proliferation of Human Liver Cancer Cells under Alternating Magnetic Field
Do Guwn Hwang,Hyeji Park 한국자기학회 2020 Journal of Magnetics Vol.25 No.4
The effects of alternating magnetic field (AMF) stimulation on the proliferation of human liver cancer cells (HepG2) under varying frequencies from 500 ㎐ to 2 ㎑ were investigated. The AMF stimulator generated a magnetic field of 5 mT with a saw tooth pulse waveform, the frequency of alternating pulses was controlled by the duty factor of the digital control circuit. HepG2 cells were cultured in a 6-well plate over a magnetic coil using a cooling system while been kept for 48 hours in an incubator. After magnetic stimulation of 0.5, 1 and 2 ㎑, the proliferation rates of the HepG2 cells saw almost no difference compared to liver cancer cells that were not stimulated. However, the proliferation rates at 1.4 ㎑ were reduced by up to 66 % compared to the non-stimulated cells. In other words, HepG2 cancer cells can be suppressed by magnetic stimulation of a certain frequency. These results are in good agreement with those from analysis of cell viability using MTT assay, a colorimetric assay used for assessing cell metabolic activity. This phenomenon of a suppression frequency may be related with various ionic flows that occur in the ion channels of cell membranes.
강한 펄스자기장 자극에 의한 적혈구 연전현상의 활동성 조사
황도근(Do Guwn Hwang) 한국자기학회 2017 韓國磁氣學會誌 Vol.27 No.3
It is widely known that pulsed magnetic field (PMF) is very useful tool to manipulate chemical and physiological processes in human body. The purpose of our study is to observe dynamics of rouleaux patterns of red blood cells (RBC) under PMF. The aggregation of RBCs or rouleaux formation is caused by fibrinogen in blood plasma. The maximum magnetic field intensity is 0.27 T and pulse time of 0.102 msec and pulse repetition rate was 1 ㎐. PMF stimulus was applied to the palm of left hand for 5, 10, 15 and 20 min. Live blood analysis was used in vitro in order to quantitatively estimate the velocity of RBC exposed to PMF stimulus. The velocity of stacked-RBC of 10 minute PMF stimulus was increased up to 8 × 10<SUP>−4</SUP>m/sec, but it decreased rapidly as the time passed. The results of present study have adduced that PMF stimulus on hand provide the improvement of RBC rouleaux formation, increase of RBC’s moving velocity as well as low blood viscosity.
교류자기장 자극에 따른 인간 간암세포와 정상세포의 성장률 차이 연구
황도근(Do Guwn Hwang),박혜지(Hyeji Park) 한국자기학회 2020 韓國磁氣學會誌 Vol.30 No.5
The difference of proliferation rates between human liver cancer cells and normal liver cells stimulated by alternative magnetic field at the frequency of 1.5 kHz and the intensity of 0.5 mT during 48 hours in incubator were investigated. The proliferation rates of liver cancer cells stimulated by the magnetic field decreased up to 79%, but the rates of normal liver cells did not change in spite of the magnetic field stimulation. It is assumed that the alternative magnetic stimulation on the living cells can influence to the proliferation rates of liver cancer cells. In order to know the influence of ion channel on magnetic field in liver cell membrane, we should study to the frequency dependence of alternative magnetic field.
황도근(Do Guwn Hwang) 한국자기학회 2014 韓國磁氣學會誌 Vol.24 No.1
The change of rouleau formation of red blood cells in the hand stimulated by pulse magnetic field having a maximum intensity of 0.27 Tesla and pulse duration of 0.102 msec was investigated. Before pulse magnetic field stimulus, the red blood cells of test subject were adjoined over ten and the flow of cells was slowed. However after the stimulus in the hand during 10 minutes, the red blood cells adjoined over tens was spreaded out each other and its motion was fast. Also the red blood cells of left hand unstimulated by pulse magnetic field were spreaded out each other, even though the right hand was stimulated during 10 minute. It prove that the rouleau formation of red blood cells can be improve in the whole body in spite of stimulus in the hand because the blood is flowing a whole body.
Uniaxial Magnetic Anistotropy of a NiO-Spin Valve Device
Won-Hyung Lee,Do-Guwn Hwang,Sang-Suk Lee 한국자기학회 2009 Journal of Magnetics Vol.14 No.1
The shape anisotropy effect of a giant magnetoresistance-spin valves (GMR-SV) device with a glass/NiO/NiFe/CoFe/Cu/CoFe/NiFe layered structure for use in the detection of magnetic property of molecules within a cell was investigated. The patterned device was given uniaxial anisotropy during the sputtering deposition and vacuum post-annealing, which was performed at 200 ℃ under a 300 Oe magnetic field. The pattern size of the device, which was prepared through the photolithography process, was 2×15 ㎛². The experimental results confirmed that the best design for a GMR-SV device to be used as a biosensor is to have both the axis sensing current and the easy axis of the pinned NiO/NiFe/CoFe triple layer oriented in the direction of the device’s width, while the easy axis of the free CoFe/NiFe bilayer should be pointed along the long axis of the device.
Exchange Bias Coupling Depending on Uniaxial Deposition Field of Antiferromagnetic FeMn Layer
Sang-Suk Lee,Do-Guwn Hwang 한국자기학회 2010 Journal of Magnetics Vol.15 No.1
The relationship between ferromagnet anisotropic magnetization and the antiferromagnet atomic spin configuration was investigated for various angles of the uniaxial deposition magnetic field of the FeMn layer in the Corning glass/Ta(5㎚)/NiFe(7㎚)/FeMn(25㎚)/Ta(5㎚) multilayer that was prepared by the ion beam sputter deposition. The exchange bias field (Hex) obtained from the measurement of the easy-axis MR loop decreased to 40 Oe at the deposition field angle of 45˚, and to 0 Oe at the angle of 90˚. When the difference between the uniaxial axis between the ferromagnet NiFe and the antiferromagnet FeMn was 90˚, the strong antiferromagnetic dipole moment of FeMn caused the weak ferromagnetic dipole moment of NiFe to rotate in the interface.