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구동 전류의 방향에 따른 PHR 센서의 투자율 측정 성능 분석
윤석수,김동영 한국자기학회 2023 韓國磁氣學會誌 Vol.33 No.2
In order to analyze the permeability measurement performance of the PHR sensor, Type A and Type B sensors with different driving current directions were fabricated. In Type A and B sensors, the magnetic field dependence of the PHR signal Vf and the signal by self-field V2f was measured, and these results were well agreed with the calculated results by single domain model. In particular, V2f was reflected the magnetic sensitivity of Vf, and increased as much as V2f by the NiFe disk array specimen placed on the sensor. The permeability measurement performance of Type A and B sensors obtained from V2f were high resolution of = 0.45 and 0.75, respectively.
CoFe/IrMn 박막에서 교환바이어스 Training 효과의 IrMn 두께 의존성 연구
윤석수,김동영 한국자기학회 2023 韓國磁氣學會誌 Vol.33 No.1
The IrMn thickness dependence of exchange bias training effect was studied in exchange coupled CoFe/IrMn(tAF) thin films. The exchange bias training effect was dominated in the range of 3 nm < tAF < 7 nm. The range was correspond to increasing the exchange bias by the pinned IrMn and decreasing the coercivity by the irreversible behavior of unpinned IrMn based on single domain model. Thus the exchange bias training effect was explained by the relaxation process by the reorientation of pinned-unpinned IrMn from initial alignment to final equilibrium state during the consecutive cycles of M-H loop.
평면홀 저항 센서의 2차 조화파 신호를 이용한 CoFeB 박막의 투자율 측정
윤석수,김동영 한국자기학회 2022 韓國磁氣學會誌 Vol.32 No.6
We measured the permeability of CoFeB thin films by using the second harmonic signals of planner Hall resistance (PHR) sensor in the low frequency range of 10 Hz~50 kHz. The low frequency permeability of CoFeB thin film was compared with the microwave permeability measured by using one-turn coil as well as the real permeability calculated by LLG equation. We confirmed that the low frequency permeability of CoFeB thin film was correspond to the initial permeability of CoFeB thin film. Thus the second harmonic signals of the PHR sensor can be applied to the low frequency permeameter with compact, high resolution and low power consumption.
줄 열처리된 비정질 마이크로 와이어의 자기임피던스 효과
윤석수,권성덕,김란,김철기 한국물리학회 2005 새물리 Vol.51 No.5
Commercial glass-covered Co-based amorphous microwires were etched in hydrofluoric acid solution to remove the glass cover. After glass removal, the 3-cm-long microwires were Joule heated by appling various dc current between 0 - 50 mA for 10 min. The Magnetoimpedance (MI) profiles and spectra were obtained by measuring the impedance during sweeps of the external magnetic field and the frequency, respectively. The maximum ginat MI (GMI) ratio was enhanced up to about 250 \% at 10 MHz by Joule heating with a dc current of 50 mA. From the analysis of circumferential permeability spectra, the enhanced GMI effect was confirmed to be caused by the circumferential anisotropy induced during the Joule heating. 유리피막을 가진 Co 주성분의 비정질 마이크로 와이어의 유리피막을 불산 용액에서 부식시켜 유리피막을 제거한 후, 0 - 50 mA 사이의 직류전류를 10분 동안 흘려주는 방법으로 줄 열처리를 하였다. 줄 열처리된 시편에 대해 자기임피던스 모양과 스펙트럼을 $-$40 Oe 에서 +40 Oe의 자기장과 100 kHz에서 10 MHz 주파수 범위 내에서 각각 측정하였다. 50 mA에서 줄 열처리된 경우 최대 자기임피던스 비 기준으로 10 MHz의 주파수에서 250 \%의 높은 자기임피던스 효과의 증대를 얻을 수 있었다. 자기임피던스 스펙트럼으로부터 얻어진 원주방향 투자율 스펙트럼을 분석하여 줄 열처리에 의해 원주방향 이방성이 유도되었으며 이로 인해 자기임피던스 효과가 증대되었음을 밝혔다.
윤석수 안동대학교 기초과학연구소 1991 基礎科學 硏究論文集 Vol.2 No.1
The theoretical analysis on the spectrum of complex dielectric permitivity at insulated electrode/conductive dielectric/partially insulated electrode interface shows two regions of Debye type dispersion due to space charge relaxation. The characteristic features of the proposed model are verified by the measurements of the complex dielectric permitivity for water, and adapted to monitoring of the hydration process of cement paste in the frequency range of 10^(4)-10^(6) Hz.
두상 혼합체의 유전 반응에 대한 deterministic fractal circuit 모델
윤석수,권성덕 안동대학교 기초과학연구소 1996 基礎科學 硏究論文集 Vol.7 No.1
일반적인 형태의 fractal two phases mixtures의 유전반응을 deterministic fractal circuit(DFC)모델을 통해 해석적으로 다룬다. 열의 수가 2로 한정된 Dissado-Hill에 의해 고려된 모델이 일반적인 열의 수를 포함하는 경우로 확장된다. 일반적인 DFC model로부터 얻어지는 교류 impedance spectrum은 fractal mixture의 기하학적인 형태에 의존하는 지수를 가지는 fractional power-law response를 보여준다. 특히 impedance의 실수부와 허수부가 같이 주파수에 대해 fractional power-law 의존성을 가지는 constant-phase-angle response의 존재 조건이 유도된다. A deterministic fractal circuit(DFC) model for the dielectric response of general fractal mixture is analytically investigated. The Dissado-Hill`s model, where the number of row in the fractal mixture was confined to two, is generalized to include arbitrary number of rows. The impedance spectrum by DFC model shows fractional power-law dependence with the exponent depending on the structure of fractal mixture. Specially the condition for the existence of constant-phase-angle response is derived.
산화철 나노입자의 결합 모양에 따른 강자성 공명 신호 분석
윤석수,김동영 한국자기학회 2023 韓國磁氣學會誌 Vol.33 No.1
The iron oxide nanoparticles (NPs) was synthesized by thermal decomposition method. The effective saturation magnetization Meff =20 2 emu/cc and g-factor = 2.12 for iron oxide NPs was obtained by using ferromagnetic resonance (FMR) technique in 2D plate coated with NPs. The FMR signals of final reaction solution including NPs was analyzed by using kittel’s resonance condition for shape effect. The FMR signals of final reaction solution divided into two different signals. The one was due to the superparamagnetic 3D sphere by the isolated NPs, the other was explained by the 1D chains structure connected by NPs.