• 한국초전도ㆍ저온공학회논문지
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• 제19권1호
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• pp.26-29
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• 2017

We studied the distribution of the current density and its magnetic-field dependence in GdBCO coated conductors with AC bias currents using low temperature scanning Hall probe microscopy. We selectively measured magnetic field profiles from AC signal obtained by Lock-in technique and calculated current distributions by inversion calculation. In order to confirm the AC measurement results, we applied DC current corresponding to RMS value of AC current and compared distribution of AC and DC transport current. We carried out the same measurements at various external DC magnetic fields, and investigated field dependence of AC current distribution. We notice that the AC current distribution unaffected by external magnetic fields and preserved their own path on the contrary to DC current.

• 한국소음진동공학회논문집
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• 제19권4호
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• pp.418-424
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• 2009

This work is the attempt to give qualitative explanations to complex magnetic phenomena which are observed in the previously proposed magnetostrictive sensor capable of ultrasonic waves and rotational speed measurement. The law of approach is adopted as analysis tool in order to account for some extraordinary output patterns and proved to be effective. The distance between the anhysteretic curve current magnetic state and the variation of anhysteretic curve by stress mainly determine the sensor output shapes and their uniqueness. It is also experimentally verified that the precisely determined bias magnetic field strength can not only remove the unusual output parts but also maximize its sensitivity.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2006년도 춘계학술대회논문집
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• pp.1154-1158
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• 2006

This investigation suggests a new non-contact type sensor that can measure flexural vibrations of a non-ferromagnetic pipe. The sensor works on the reversed Lorentz force mechanism; however, anti-symmetric bias magnetic field suggested in this work should be applied to measure bending vibration of a non-ferromagnetic pipe. The importance of the suggested magnetic field is verified by a series of experiments. The sensor is applied to the bending vibration measurement and modal testing of an aluminum pipe and shows satisfactory working performance compared to others.

• Journal of Magnetics
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• 제8권1호
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• pp.36-44
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• 2003

Three topics which are related to technologies for developing of large capacity MRAM over Gbits are reviewed. First, it is stressed that inelastic-electron-tunnel-tunneling spectroscopy(IETS) is a powerfull method to investigate the interface state between magnetic electrodes and insulator. Second, magnetic tunnel junctions with small bias voltage dependence are introduced. Finally, fabrication method of carbon masks for very small magnetic tunnel junctions is demonstrated. These three topics were presented at 47^{th} MMM 2002 conference and each paper will appear in the proceedings.

• 한국초전도ㆍ저온공학회논문지
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• 제19권3호
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• pp.23-26
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• 2017

We have studied magnetic and transport properties of NbN/FeN/Cu/FeN/FeMn spin-valve structure. In-plane magnetic moment exhibited typical hysteresis loops of spin valves in the normal state of NbN film at 20 K. On the other hand, the magnetic hysteresis loop in the superconducting state exhibited more complex behavior in which exchange bias provided by antiferrmagnetic FeMn layer to adjacent FeN layer was disturbed by superconductivity. Because of this, the ideal superconducting spin-valve effect was not detected. Instead the stray field originated from unsaturated magnetic states dominated the transport properties of NbN/FeN/Cu/FeN/FeMn multilayer.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2002년도 추계학술대회 논문집 전기물성,응용부문
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• pp.219-222
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• 2002

In this paper, some parameters are studied for the performance improvement of a bulk optical magnetic-field sensor. The performance of optical magnetic-field sensor is influenced by optical intensity change and wavelength change of light source, and phase shift so called optical bias mismatch. A magnetic field measuring system based on optical Faraday sensor is implemented and tested in the current range from 10 ampere to 200 ampere. The test result shows implemented system has goof linearity.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2005년도 제36회 하계학술대회 논문집 B
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• pp.1506-1508
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• 2005

VCO(voltage controlled oscillator) using mobile communication device decides direct characteristics as parts that affect important in stable oscillation and distortion characteristics of system. VCO used 900 MHz band was designed by the transformation of Colpitts circuit form use ADS that consider Q-factor to minimize phase noise. VCO manufactured together evaluation board and voltage control oscillator to FR-4 PCB. VCO experimented chracteristics after control through resonance department tuning. In our research, the designed VCO has 15.5 dBm output level at the bias condition of 6V and 10mA and the operating frequency range of 917 MHz$\sim$937 MHz band. Phase noise is -98.28 dBc/Hz at 1 MHz frequency offset from the carrier.

• Journal of Magnetics
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• 제16권3호
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• pp.211-215
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• 2011

The dynamic magnetostriction characteristics of an Fe-based nanocrystalline FeCuNbSiB alloy are investigated as a function of the dc bias magnetic field. The experimental results show that the piezomagnetic coefficient of FeCuNbSiB is about 2.1 times higher than that of Terfenol-D at the low dc magnetic bias $H_{dc}$ = 46 Oe. Moreover, FeCuNbSiB has a large resonant dynamic strain coefficient at quite low Hdc due to a high mechanical quality factor, which is 3-5 times greater than that of Terfenol-D at the same low $H_{dc}$. Based on such magnetostriction characteristics, we fabricate a new type of transducer with FeCuNbSiB/PZT-8/FeCuNbSiB. Its maximum resonant magnetoelectric voltage coefficient achieves ~10 V/Oe. The ME output power reaches 331.8 ${\mu}W$ at an optimum load resistance of 7 $k{\Omega}$ under 0.4 Oe ac magnetic field, which is 50 times higher than that of the previous ultrasonic-horn-substrate composite transducer and it decreases the size by nearly 86%. The performance indicate that the FeCuNbSiB/PZT-8/FeCuNbSiB transducer is promising for application in highly efficient magnetoelectric energy conversion.

• 한국정보통신학회논문지
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• 제20권2호
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• pp.445-450
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• 2016

본 논문은 함정의 형상이 탈자 이후에 함정에 형성되는 수직자화에 미치는 영향에 대해 조사하였다. 선박의 전면 전개도로부터 함정의 형상을 삼각형, 사각형, 원형으로 선택하여 지자계에 의한 수직방향의 유도자화를 FEM 정자장 해석으로 조사하였다. 탈자과정 중에 자화에 의한 자계를 측정하였으며, 탈자 이후 성분분리를 통해 영구자화에 의한 자계의 수평 및 수직성분의 크기를 바이어스 자계의 변화에 따라 조사하였다. 이 실험으로부터 함정의 형상을 고려하는 탈자처리 방법이 필요하며 방법으로 선수와 선미 쪽에 권선 간격을 좁게 하여 함정의 중앙부분보다 비교적 더 큰 자계가 인가되도록 하는 것이 바람직하다는 것을 알았다.

• 한국재료학회:학술대회논문집
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• 한국재료학회 2003년도 추계학술발표강연 및 논문개요집
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• pp.212-212
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• 2003

Many of the spin valve multilayer structures with FeMn as antiferromagnetic layer consist of a NiFe/FeMn/NiFe trilayer where the bottom NiFe layer is the seed layer to facilitate the growth of (111) gama-FeMn antiferromagnetic phase and the top NiFe layer forms the pinned layer[1], In this study, exchange bias of bottom NiFe layer has been investigated as functions of thicknesses of top and bottom NiFe in NiFe/FeMn/NiFe, prepared by rf magnetron sputtering, MH-loop was measured by vibration sample magnetometer (VSM). Two hysteresis loops are corresponded to bottom and top layers, similar to reported loops in spin valve structure. Exchange bias of bottom NiFe could be induced by the interfacial coupling between bottom NiFe and FeMn. But those coupling are strongly dependent on the top and bottom NiFe thicknesses, revealing anomalous character ul exchange bias of bottom NiFe layer.