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교환 결합력을 갖는 NiFe/CoFe 박막에서 강자성 공명 신호의 각도 의존성 연구
윤석수(Seok Soo Yoon),김동영(Dong Young Kim) 한국자기학회 2022 韓國磁氣學會誌 Vol.32 No.5
The angular dependence of ferromagnetic resonance signal showed single resonance mode (H<SUB>r</SUB>) at near in-plane (θ<SUB>H</SUB> ≈ 0), and dual resonance modes (H<SUB>r1</SUB> < H<SUB>r2</SUB>) at near normal to plane (θ<SUB>H</SUB> ≈ 90˚) in NiFe(100 ㎚)/CoFe(5 ㎚) thin film, respectively. The single mode H<SUB>r</SUB> was due to effective magnetic properties by the ferromagnetic exchange coupled NiFe/CoFe bilayers. The H<SUB>r1</SUB> of dual mode was same as the ferromagnetic resonance field of the NiFe single layer, and H<SUB>r2</SUB> of dual mode was explained by the ferromagnetic exchange coupling effect.
Cu 코어/Ni<SUB>80</SUB>Fe<SUB>20</SUB> 쉘 복합와이어를 넣은 솔레노이드 코일 인덕터를 이용하는 L/R 오실레이터 기반 지자기 센서
윤석수(Seok Soo Yoon),김동영(Dong Young Kim),최재연(Jae Yeon Choi),이상훈(Sang Hun Lee) 한국자기학회 2019 韓國磁氣學會誌 Vol.29 No.1
In recent, PNI sensor corporation has been released geomagnetic field sensor with high performance. This sensor uses a new principle measuring the period of digital output pulse of L/R oscillator circuit which is connected to the solenoid coil inductor wound on high permeability amorphous wire. In this paper, we design L/R oscillator circuit based on the PNI’s principle and connect the circuit to the solenoid coil inductor containing Cu core/Ni<SUB>80</SUB>Fe<SUB>20</SUB> shell composite wire fabricated by electrodeposition. We investigate applicability of this system to geomagnetic field sensor.
NiFe 박막에서 교환 뻣뻣함 상수의 각도 의존성 분석
윤석수(Seok Soo Yoon),김동영(Dong Young Kim) 한국자기학회 2017 韓國磁氣學會誌 Vol.27 No.5
The exchange stiffness constant A<SUB>ex</SUB> was linearly propositional to the difference of spin wave resonance field H<SUB>SWR</SUB> and ferromagnetic resonance field H<SUB>FMR</SUB>. In this work, we measured the H<SUB>SWR</SUB> and HFMR with in-plane angles in order to analyze the angular dependence of A<SUB>ex</SUB> in NiFe thin film with thickness of 100 ㎚. The Aex of NiFe thin film was shown isotropic behavior not depending on the inplane angles. The measured value of A<SUB>ex</SUB> was 10.9 × 10<SUP>−7</SUP> erg/cm and its value should be applied to the spin wave devices.
CoFe/MnIr 박막에서 MnIr 두께에 따른 교환 결합 특성 분석
윤석수(Seok Soo Yoon),김동영(Dong Young Kim) 한국자기학회 2019 韓國磁氣學會誌 Vol.29 No.5
We analyzed MnIr thickness dependence of exchange bias fields (H<SUB>ex</SUB>) and rotatable anisotropy fields (H<SUB>ra</SUB>) by the ferromagnetic resonance method in 300℃ annealed CoFe/MnIr(t<SUB>AF</SUB>) bilayers. The critical thickness of MnIr was t<SUB>c</SUB> = 3.0 nm, the H<SUB>ex</SUB> as well as H<SUB>ra</SUB> was appeared at t<SUB>AF</SUB> > t<SUB>c</SUB>. It was due to the grain size distribution of the MnIr. The Hex was induced by fixed AF spins of MnIr grains thicker than t<SUB>c</SUB>, while H<SUB>ra</SUB> was induced by rotatable AF spins of MnIr grains thinner than t<SUB>c</SUB>. The exchange coupling field H<SUB>ec</SUB> = H<SUB>ra</SUB> + H<SUB>ex</SUB> did not depend on the MnIr thickness at t<SUB>AF</SUB> > t<SUB>c</SUB>, therefore, we concluded that the exchange coupling energy did not depend on the MnIr thickness at t<SUB>AF</SUB> > t<SUB>c</SUB>.
교환 바이어스 특성을 갖는 MnIr/NiFe 박막의 비등방성 교환 뻣뻣함 상수 특성
윤석수(Seok Soo Yoon),김동영(Dong Young Kim) 한국자기학회 2021 韓國磁氣學會誌 Vol.31 No.6
The ferromagnetic resonance field and spin wave resonance field with in-plane angles Φ<SUB>H</SUB> were measured in order to analyze the angular dependence of exchange stiffness constant A<SUB>ex</SUB> in exchange biased MnIr/NiFe thin film. The A<SUB>ex</SUB> of MnIr/NiFe thin film showed an anisotropic behavior such as A<SUB>ex</SUB> =A<SUB>0</SUB> + A<SUB>eb</SUB>cosΦ<SUB>H</SUB>. The isotropic exchange stiffness constant A<SUB>0</SUB> was due to the exchange stiffness constant of NiFe, while anisotropic exchange stiffness constant A<SUB>eb</SUB> was due to the exchange bias field.
NiFe/MnIr 박막에서 교환 바이어스의 각도 의존성 연구
윤석수(Seok Soo Yoon),김동영(Dong Young Kim) 한국자기학회 2017 韓國磁氣學會誌 Vol.27 No.1
In this report, we calculated the angular dependence of exchange bias (H<SUB>ex</SUB>) by using single domain model in exchange coupled ferromagnetic (F)/antiferromagnetic (AF) bilayers, which results with AF thickness (t<SUB>AF</SUB>) were used for the analysis of measured ones in NiFe/MnIr bilayers. Angular dependence of Hex calculated at t<SUB>AF</SUB> > t<SUB>c</SUB> showed typical unidirectional behaviors, however, calculated one at 0.5t<SUB>c</SUB> < t<SUB>AF</SUB> < t<SUB>c</SUB> showed peculiar angular behaviors by fixed AF spins at specified angle near θ<SUB>H</SUB>= 90°. Angular dependence of H<SUB>ex</SUB> measured in NiFe/MnIr (20 nm) bilayers showed typical unidirectional behaviors. However, measured one in NiFe/MnIr (4 nm) bilayers showed mixed behaviors including both of unidirectional and peculiar angular behaviors, which was explained by the grain size distribution of polycrystalline MnIr.
교환 결합력을 갖는 CoFe/MnIr 박막에서 강자성 공명 선폭의 각도 의존성 연구
윤석수(Seok Soo Yoon),김동영(Dong Young Kim) 한국자기학회 2016 韓國磁氣學會誌 Vol.26 No.2
We analyzed the angular dependence of ferromagnetic resonance linewidth in exchange coupled CoFe/MnIr bilayers. The maximum and minimum linewidth was observed in the easy and hard direction of unidirectional anisotropy by exchange coupling, respectively, and it was well agreed with the angular dependence of exchange bias field. The maximum linewidth was due to the twist of CoFe magnetization near CoFe/MnIr interface from direction of pinned MnIr spin to direction of applied magnetic field. While, minimum linewidth more higher than that of CoFe was related to rotatable anisotropy field, and explained by easy axis distribution of MnIr grains.
교환 결합력을 갖는 CoFe/MnIr(2.5 ㎚) 박막의 회전 이방성 자기장 특성
윤석수(Seok Soo Yoon),김동영(Dong Young Kim) 한국자기학회 2017 韓國磁氣學會誌 Vol.27 No.3
The rotatable anisotropy effect was observed in the ferromagnetic resonance measurement in exchange coupled ferromagnetic/antiferromagnetic thin films and it was due to rotation of antiferromagnetic layer by the exchange coupling energy. We analyzed the CoFe thickness dependence of rotatable anisotropy field and ferromagnetic resonance linewidth in exchange coupled CoFe(t<SUB>F</SUB>)/MnIr(2.5 ㎚) thin films. The rotatable anisotropy field was inversely propositional to the CoFe thickness and it was well fitted by the rotatable anisotropy energy of 0.96 erg/㎠. The ferromagnetic resonance linewidth were linearly propositional to the rotatable anisotropy field in t<SUB>F</SUB> < 50 ㎚, while it was more dominated by the eddy current effect in t<SUB>F</SUB> > 50 ㎚.
합성형 반강자성 결합 재료의 자기장 세기에 따른 토오크 신호 분석
윤석수(Seok Soo Yoon),전우상(Woo Sang Jun),김동영(Dong Young Kim) 한국자기학회 2011 韓國磁氣學會誌 Vol.21 No.3
We have analyzed the torque signals measured in synthetic antiferromagnetic (SAF) coupled CoFeB/Ru/CoFeB thin film, which signals were drastically changed at flopping field (H<SUB>F</SUB>) and saturation field (H<SUB>s</SUB>). The minimum value of negative uniaxial anisotropy constant (? K₁) was appeared at H<SUB>F</SUB>. The ? K₁ was due to the zero net magnetization by the antiferromagnetic coupling between two ferromagnetic layers. Whereas, the biaxial anisotropy constant (K₂) was induced in the field range of H<SUB>F</SUB> < H < H<SUB>s</SUB>. The induced K₂ was originated from deviation angles between magnetization directions of two ferromagnetic layers. And at H > H<SUB>s</SUB>, intrinsic uniaxial anisotropy constant of CoFeB layer was observed. These change of the anisotropy constant with magnetic field was explained by the magnetization process of two ferromagnetic layers based on Stoner-Wohlfarth model calculation for SAF thin film.
PHR 센서의 자체 자기장을 이용한 자성 비드 신호 탐지
윤석수(Seok Soo Yoon),김동영(Dong Young Kim),이재훈(Jae-Hoon Lee),김성준(Sung-Joon Kim),김철기(Cheol-Gi Kim) 한국자기학회 2019 韓國磁氣學會誌 Vol.29 No.5
We analyzed the magnetic field dependence of V<SUB>SF</SUB> signal, which second harmonic signal was generated by self-field of planner Hall resistance (PHR) sensor. The V<SUB>SF</SUB> signal was proportional to the product of sensitivity of PHR sensor and self-field. The magnetic field dependence of bead signal detected by V<SUB>SF</SUB> signal showed maximum value at H = 0. The bead signal detected by using the Self-field sensor operated at H = 0 showed linear behavior up to 1/100 bead concentration. Thus, the Self-field sensor can be applied to the external field free biosensor.