• Proceedings of the KIEE Conference
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• 2000.07c
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• pp.1717-1719
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• 2000

DLC films are deposited by using an FCVA deposition system with a mirror-type magnetic field configuration. Permanent magnets and: magnetic yokes around the cathode have been observed to enhance the mobility of arc spots on the cathode and the stability of arc plasma, Effects of reactor pressures and substrate biases on structural properties of DLC films deposited are investigated. The results show that the highest $sp^{3}/sp^{2}$ fraction is obtained when the films are deposited at a pressure of $3{\times}10^4$ Torr and a bias voltage of - 50 V. The variation of the structural properties due to thermal stress up to 500$^{\circ}C$ is also examined.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.28 no.11
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• pp.1703-1710
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• 2004

The objective of this investigation is to formulate and carry out the topology optimization of a magnetic system consisting of permanent magnets and yokes. Earlier investigations on magnetic field topology optimization have been limited on the design optimization of yokes or permanent magnets alone. After giving the motivation for the simultaneous design of permanent magnets and yokes, we develop the topology optimization formulation of the coupled system by extending the technique used in structural problems. In the present development, we will also examine the effects of the functional form for permeability penalization on the optimized topology.

• Korean Journal of Optics and Photonics
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• v.4 no.4
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• pp.474-479
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• 1993

An interferometric fiber-optic magnetic field sensor is constructed by bonding a Co-Fe-B metallic glass transducer developed here by the melt-spun method to a single mode fiber arm in the fiber Mach-Zehnder interferometer and is tested. The bias field for the peak ac-sensitivity was observed near 0.97 Oe and the minimum detectable magnetic field was 3.9${\times}10^{-5}$ Oe(rms)/${\sqrt{Hz}}$ a 3 kHz. The output of the ac field sensor becomes saturated near the input signal level of 1 Oe(rms). The Co- Fe-B transducer exhibits peak response near 500 Hz.

• Korean Journal of Optics and Photonics
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• v.2 no.3
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• pp.139-148
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• 1991

A fiber-optic magnetic sensor system for the detection of small ac magnetic field(200Hz-2 kHz) was constructed. Magnetic field sensing part was fabricated by bonding a section of optical fiber to amorphous metallic glass(2605SC) having large magnetostriction effect. And with the directional coupler, all fiber type Mach-Zehnder interferometer was constructed to measure the variation of the external magnetic field by translating it into the optical phase shift in the interferometer. The signal fading problem of the interferometer, which is due to random phase drifts originated from the environment, i.e., temperature fluctuation, vibrations, etc., was elliminated by feedback phase compensation. This allows the sensitivity to be maintained at the maximum by keeping the interferometer in quadrature phase condition. The frequency response of metallic glass was found to be nearly flat in the range of 90 Hz-2 kHz and dc bias field for the maximum ac response was 3.5 Oe. The interferometer output showed good linearity over the range $\pm$0.5 Oe. For 1 kHz ac magnetic field the scale factor S and the minimum detectable magnetic field were measured to be 8.0 rad/Oe and $3X10^{-6} Oe/\sqrt{Hz}$at 1 Hz detection bandwidth respectively.

• Journal of the Korean Magnetics Society
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• v.18 no.5
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• pp.180-184
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• 2008

The relation of ferromagnet anisotropic magnetization and the antiferromagnet atomic spin configuration has been investigated for variously angles of unidirectional deposition magnetic field of FeMn layer in Corning glas/Ta(5 nm)/NiFe(7 nm)/FeMn(25 nm)/ Ta(5 nm) multilayer prepared by ion beam deposition. Three unidirectional deposition angles of FeMn layer are $0^{\circ},\;45^{\circ}$, and $90^{\circ}$, respectively. The exchange bias field ($H_{ex}$) obtained from the measuring easy axis MR loop was decreased to 40 Oe in deposition angle of $45^{\circ}$, and to 0 Oe in the angle of $90^{\circ}$. One other side hand, $H_{ex}$ obtained from the measuring hard axis MR loop was increased to 35 Oe in deposition angle of $45^{\circ}$, and to 79 Oe in the angle of $90^{\circ}$. Although the difference of uniderectional axis between ferromagnet NiFe and antiferromagnet FeMn was 90o, the strong antiferromagnetic dipole moment of FeMn caused to rotate the weak ferromagnetic dipole moment of NiFe in the interface. This result implies that one of origins for exchange coupling mechanism depends on the effect of magnetic field angle during deposition of antiferromgnet FeMn layer.

• Korean Journal of Materials Research
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• v.11 no.6
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• pp.477-482
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• 2001

The velocity changes of magneto surface acoustic wave (MSAW) have been investigated in the MSAW devices composed of wedge type transducer and as-sputtered ($Fe_{1-x}$ $Co_{x}$ )$_{89}$ $Zr_{ 11}$ (x=0~1.0)amorphous films on glass substrates. The velocity changes of devices depended sensistively on exciting frequency of MSAW, applying the DC bias magnetic field. film thickness and film composition. Particularly. it was conformed that velocity changes increased with the increase of the exciting frequency of MSAW and the thickness of magnetic films. A device deposited x= 0.8 film along the MSAW propagation direction among the devices exhibited a large velocity change of 0.062% at 8.7 MHz for the applied field of 70 Oe.

• Proceedings of the KIEE Conference
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• 1997.07d
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• pp.1364-1366
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• 1997

Planar type magnetized inductively coupled plasma etcher has been built. The density and temperature of Ar plasma are measured as a function of rf power, external magnetic field, and pressure. The oxide etch rate and selectivity to polysilicon are measured as the above mentioned conditions and self-bias voltage.

• Journal of the Korean Magnetics Society
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• v.5 no.4
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• pp.299-303
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• 1995

In order to improve the read-out signal waveform, a shielded magnetoresistive (SMR) head has been designed and studied by applying the transmission-line model. The bias and signal field distribution, the voltage output, the harmonic output signal and resistance value of MR element are simulated as functions of bias current and recording displacement. The results show that the SMR head has good linear character with respect to the medium recording signal in high recording frequency of about 2.5 MHz. The amplitude and waveform of reroduction signal have been obviously improved. The saturation effect on the symmetry and amplitude of reproducing output have also been analyzed.

• Investigative Magnetic Resonance Imaging
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• v.22 no.4
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• pp.218-228
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• 2018

Purpose: The objective of this study is to determine the effect of physical changes on MR temperature imaging at 7.0T and to examine proton-resonance-frequency related changes of MR phase images and T1 related changes of MR magnitude images, which are obtained for MR thermometry at various magnetic field strengths. Materials and Methods: An MR-compatible capacitive-coupled radio-frequency hyperthermia system was implemented for heating a phantom and swine muscle tissue, which can be used for both 7.0T and 3.0T MRI. To determine the effect of flip angle correction on T1-based MR thermometry, proton resonance frequency, apparent T1, actual flip angle, and T1 images were obtained. For this purpose, three types of imaging sequences are used, namely, T1-weighted fast field echo with variable flip angle method, dual repetition time method, and variable flip angle method with radio-frequency field nonuniformity correction. Results: Signal-to-noise ratio of the proton resonance frequency shift-based temperature images obtained at 7.0T was five-fold higher than that at 3.0T. The T1 value increases with increasing temperature at both 3.0T and 7.0T. However, temperature measurement using apparent T1-based MR thermometry results in bias and error because B1 varies with temperature. After correcting for the effect of B1 changes, our experimental results confirmed that the calculated T1 increases with increasing temperature both at 3.0T and 7.0T. Conclusion: This study suggests that the temperature-induced flip angle variations need to be considered for accurate temperature measurements in T1-based MR thermometry.

• Korean Journal of Materials Research
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• v.3 no.4
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• pp.327-335
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• 1993

Using a RF cylindrical magnetron operated with two electromagnets having a Helmholz configuration, RF magnetron plasma properties and characteristics of reactive ion ething of Si were investigated as a function of applied magnetic field strengths using 3mTorr $CF_4/H_2$ and $CHF_3$. Also, I-V characteristics of Schottky diodes, which were made of silicons etched under different applied magnetic field strengths and gas environments, were measured to investigate the degree of radiation damage during the reactive ion etching. As the magnetic field strent;th increased, ion densities and radical densities of the plasmas were increased linearly, however, the dc self-bias voltages induced on the powered electrode, where the specimen are located, were decreased exponentially. Maximum etch rates, which were 5 times faster than that etched without applied magnetic filed, were obtained using near lOOGauss, and, under these conditions, little or no radiation damages on the etched silicons were found.