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온도에 따른 비정질 금속 Co66Fe₄Ni₁B₁₄Si15의 자기 임피던스 효과
김용국(Y. K. Kim),김택기(T. K. Kim),김성일(S. I. Kim),이희복(Heebok Lee) 한국자기학회 1998 韓國磁氣學會誌 Vol.8 No.1
The temperature dependence of the magnetoimpedance (MI) effect is important both for scientific study and for thermal stability of MI sensors. We have performed the measurement of MI effect in amorphous Co_(66)Fe₄Ni₁B₁₄Si_(15) (Metglas 2714A) ribbon from a cryogenic chamber where the temperature of the sample can vary from 10 K to 300 K. The ac current was fixed at 10 ㎃ for all measured frequencies ranging from 100 ㎑ to 10 ㎒.<br/> The magnetoimpedance ratio (MIR) was revealed the drastic increment as a function of MIR (T) = MIR (0) exp(cT²) where c is a constant. The measured MIR values at room temperature are usually 2-3 times larger than the data measured at 10 K for all measured frequencies. However, the shapes of the MIR curves are remained. This result shows the potential application of the MI effect for a temperature sensor. The frequency dependence of MIR has shown the typical tendency where the maximum values of MIR are increasing and also the shapes of MIR curves are getting broader as the measured frequency increases.
다결정 자화곡선을 이용한 콘이방성물질의 스핀재배열각 결정법 : Nd₂Fe₁₄B에의 적용
김윤배(Y. B. Kim),Jin Han-min(Jin Han-min),김만중(M. J. Kim),김택기(T. K. Kim) 한국자기학회 1998 韓國磁氣學會誌 Vol.8 No.3
A new method to calculate the spin reorientation angle of cone anisotropy from magnetization curves of magnetically aligned powder is suggested. The spin reorientation angle of polycrystalline Nd₂Fe₁₄B determined by this method coincided with the results obtained from torque magnetometry or magnetization measurements on single crystal. The underestimation of about 9% is expected if the basal plane anisotropy is neglected in determination of the spin reorientation angle of Nd₂Fe₁₄B at 4.2 K.
(Nd₁-xRx)₂Fe₁₄B (R=Y, Pr)의 자기특성
김만중(M. J. Kim),김윤배(Y. B Kim),김희태(H. T. Kim),김택기(T. K. Kim) 한국자기학회 1998 韓國磁氣學會誌 Vol.8 No.5
Spin reorientation and magnetocrystalline anisotropy of magnetically aligned (Nd_(1-x)Rx)₂Fe₁₄B (R=Y, Pr) power were studied. The spin reorientation temperature (T_(SR)) of (Nd_(1-x)Pr_x)₂Fe₁₄B decreases linearly by increasing Pr-substitution with the ratio of △T_(SR)=-1.35 K/Pr at.% in composition range of 0≤x≤0.75. The spin reorientation temperature of (Nd_(1-x)Yx)₂Fe₁₄B decreases by increasing Pr-substitution to 118 K (x = 0.5) then increases to 122 K (x = 0.75). The spin reorientation angle at 4.2 K decreases by increasing rare earth substitution with the ratio of △SRA = -0.073°/Y at.% and △SRA = -0.258°/Pr at.% in composition range of 0≤x≤0.5. The spin reorientation is expected to disappear at x≥0.9 in case of (Nd_(1-x)Yx)₂Fe₁₄B and at x≥0.8 in case of (Nd_(1-x)Pr_x)₂Fe₁₄B.
김동환(D. H. Kim),권혁무(H. M. Kwon),김택기(T. K. Kim),김희태(H. T. Kim),김윤배(Y. B. Kim) 한국자기학회 1995 韓國磁氣學會誌 Vol.5 No.5
The nitrogenation process and magnetic properties of Sm₂Fe_(17)Nx (0 ≤ x ≤ 3) were investigated. During the initial nitrogenation process, the nitrogen content had linear relation with the square root of nitrogenation time, and the activation energy for the process was calculated to be 102.4 kJ/㏖. The magnetic properties of Sm₂Fe_(17)Nx were strongly dependent on the nitrogen content and the composition having Sm₂Fe_(17)N_(2.8) showed optimum magnetic properties with a Curie temperature of 450 oC. The intrinsic magnetic properties of the nitride at room temperature were Ms = 1147 emu/㎤, K₁ = 4.6 × 10^7 erg/㎤, K₂ = 6.0 × 10^7 erg/㎤ and H_A = 290 kOe, respectively.
일축이방성 다결정의 자화곡선을 이용한 포화자화 및 결정자기이방성상수 결정에서의 오차분석
김만중(M. J. Kim),허진(J. Hur),김윤배(Y. B. Kim),김택기(T. K. Kim) 한국자기학회 1999 韓國磁氣學會誌 Vol.9 No.4
Errors of saturation magnetization and magnetocrystalline anisotropy constant determined by magnetization curve of magnetically aligned uniaxial power were analyzed. In case of alignment factor (θ0)=10°, magnetic constant errors of Nd₂Fe₁₄B were calculated to be error of Ms ≒ 1 % and error of K₁ ≒ 13 %, respectively, and magnetic constant errors of Ba-ferrite were calculated to be error of Ms ≒ 1 % and error of K₁ ≒ 17 %. In this method, Ms was found to be determined with high accuracy. High alignment is desirable for high accuracy.
Ndx(Fe0.9Co0.1)90-xB6Nb₃Cu₁(x=3, 4, 5) 초미세결정립합금의 자기특성
조용수(Y. S. Cho),김만중(M. J. Kim),천정남(Z. N. Qian),김택기(T. K. Kim),박우식(W. S. Park),김윤배(Y. B. Kim) 한국자기학회 1995 韓國磁氣學會誌 Vol.5 No.5
Magnetic properties of Nd_x(Fe_(0.9)Co_(0.1))_(90-x)B_6Nb₃Cu₁(X = 3, 4, 5) melt-spun alloys with 6 at% B content were studied aiming for finding out a new α-Fe based Nd-Fe-B nanocrystalline alloy with good hard magnetic properties. Nd_x(Fe_(0.9)Co_(0.1))_(90-x)B_6Nb₃Cu₁ melt-spun alloys prepared by RSP crystallized to nanocrystalline phase. An optimally annealed Nd₃(Fe_(0.9)Co_(0.1))_(87)B_6Nb₃Cu₁ melt-spun alloys had larger volume ratio of α-Fe (Co) than that of higher Nd content alloy and showed high remanence of about 1.6 T. On the contrary, the increase of Nd content in Nd_x(Fe_(0.9)Co_(0.1))_(90-x)B_6Nb₃Cu₁ alloys gave rise to gradual increase of an amount of Nd₂(Fe, Co)₁₄B phase and improved coercivity. An optimally annealed Nd_5(Fe_(0.9)Co_(0.1))_(85)B_6Nb₃Cu₁ alloy showed the most improved hard magnetic properties. The remanence, coercivity and energy product of the alloy were 1.35 T, 219 ㎄/m (2.75 kOe), and 129 kJ/㎥ (16.2 MGOe), respectively.
Fe - B - Al계 비정질합금의 자왜 및 자기탄성효과
조용수(Y. S. Cho),김윤배(Y. B. Kim),김창석(C. S. Kim),김택기(T. K. Kim) 한국자기학회 1993 韓國磁氣學會誌 Vol.3 No.2
Saturation magnetostriction and magnetoelastic properties of amorphous Fe_(82)B_(18-x)Al_x and Fe_(80)B_(20-x)Al_x alloys have been studied. Saturation magnetostriction of the alloys has increased according to the increase of Al content. The amorphous Fe_(82)B₁₄A₄ alloy shows the highest saturation magnetostriction of 45 ppm among the alloy systems. The ratio of maximum magnetic induction change to tensile stress of this alloy is about 0.026 Tㆍ㎟/N, and it is considered to be applicable for a high resolution mechanical sensor.
α-(Fe, Co)기 Nd - (Fe, Co) - B - Nb - Cu 초미세결정립합금의 자기특성에 미치는 Nd의 영향
조덕호(Duck-Ho Cho),조용수(Y. S. Cho),김택기(T. K. Kim),송민석(M. S. Song),김윤배(Y. B. Kim) 한국자기학회 1999 韓國磁氣學會誌 Vol.9 No.3
Magnetic properties and microstructure of nanocrystalline α-(Fe, Co)-based Nd-(Fe, Co)-B-Nb-Cu alloys have been investigated. Ndx(Fe_(0.9)Co_(0.1))_(90-x)B_6Nb₃Cu₁(x = 2, 3, 4, 5, 6) alloys prepared by rapid solidification process show amorphous phase except the one with x = 2. By a proper annealing, the amorphous phase in the alloy is changed to a nanocrystalline phase. It is confirmed that the nanocrystalline alloys are composed of α-(Fe, Co) and Nd₂(Fe, Co)₁₄B₁ phase. The optimally annealed Nd₃(Fe_(0.9)Co_(0.1))_(87)B_6Nb₃Cu₁ alloy shows the highest remanence of 1.55 T. The coercivity increases with the increase of Nd content. The maximum coercivity of 4.6 kOe is obtained from an optimally annealed Nd_6(Fe_(0.9)Co_(0.1))_(84)B_6Nb₃Cu₁ alloy, resulting in the maximum energy product of 10.6 MGOe.
MnSbX(X=Pt, Ag) 합금막의 미세구조 및 자기광학적 특성
송민석(M. S. Song),이한춘(H. C. Lee),김택기(T. K. Kim),김윤배(Y. B. Kim) 한국자기학회 1998 韓國磁氣學會誌 Vol.8 No.3
Crystal structures and magneto-optical properties of (Mn_(0.5-z)Sb_(0.5+z))_(100-y)Pt_y(0<z<0.03, 4.1<y<21.7) and (Mn_(0.5-z)Sb_(0.5+z))_(100-y)Ag_y(0<z<0.08, 2.1<y<11.3) alloy films prepared by RF magnetron sputtering have been studied by X-ray diffractometer, vibrating sample magnetometer, torque magnetometer, Kerr loop tracer. The crystal structure of MnSbPt and MnSbAg films annealed at 300℃ are C1b-type with fee and NiAs-type with hcp, respectively. The MnSbAg films have a texture which the c-axis orientation is perpendicular to the film plane by annealing at 300 ℃ for less than 3 hours. The perpendicular anisotropy constants of the Mn_(47.4)Sb_(47.5)Ag_(5.1) film annealed at 300 ℃ for 3 hours are K₁=6.6×10^5 erg/㎤ and K₂=1.9×10^5 erg/㎤. The Kerr rotation angle of MnSbPt films increases but that of MnSbAg film decreases by decreasing incident wavelength within the range of 700≤λ≤1000 ㎚. High polar Kerr angles of 1.7° (λ=700 ㎚) and 0.6° (λ=1000 ㎚), 0.2° (λ=700 ㎚) and 0.97° (λ=1000 ㎚) have been obtained from Mn_(41.1)Sb_(44.9)Pt_(14.0) and Mn_(47.4)Sb_(47.5)Ag_(5.1) alloy films, respectively.