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아크용해에 의해서 제작된 FeCo에 기초한 연자성체의 자기적 성질에 대한 냉간 롤링과 열처리 효과
김정기,한경훈,이상문,정재윤,신경호 한양대학교 자연과학연구소 2001 自然科學論文集 Vol.20 No.-
최대출력 3.5kw인 고주파에 의한 아르곤 플라즈마 분위기에서 제작된 시료인 Fe0.6 Co0.38(BN)0.02의 결정구조와 자기적 성질을 상온에서의 X선 회절과 진동시료자력계를 이용한 자기이력곡선 측정 방법의 의해서 연구하였다. 시료는 수압기로 9.000Nl㎠의 압력을 가하여 (1)알약형태로 제작하여 (2)냉간롤링과 (3)600℃와 800℃로 열처리를 하였다. X선 회절결과는 시료들의 결정구조가 Fe와 동일한 bcc 결정구조이며, 800℃열처리에 의해서 시료 내부에 존재하는 잔류응력이 제거되어 졌음을 보인다. 롤링에 의한 시료 두께 감소율이 증가함에 따라서 포화자화에 잔류자화는 회절선이동과 함께 증가하였고, 이들 값들을 롤링방향에도 의존함을 보았다. 반면 보자력은 임의의 시료두께 감소율(65%) 이상부터 감소하였다. 또한 열처리온도가 증가함에 따라서 잔류자화와 보자력은 선폭의 변화와 함께 감소하지만 포화자화는 열처리온도와 무관하게 거의 일정한 값을 갖는다. 이는 롤링과 열처리효과에 의해서 시료내부에 존재하는 개재물과 잔류응력이 제거되어 자벽이동이 용이해졌음을 의미하며, 또한 롤링에 의해서 동족원자쌍이 생성되어 롤링방향에 평행한 국부 유도자화용이축이 생성되었음을 의미한다. The crystallographic and magnetic properties of Fe0.6 Co0.38(BN)0.02 synthesized by microwave arc-melting with the maximum power of 3.5KW have been studied by the methods of x-ray diffraction and by the magnetic hysteresis using vibrating sample magnetometer at room temperature. The samples were prepared in a form of (1)pellet pressed under the pressure of 9.000Nl㎠ (2)cold rolled and then (3)heat treated at 600℃ and 800℃. The x-ray diffraction patterns show that the crystal structure of the samples are bcc as same as that of Fe with a good uniformity. A residual stress, which exists in the cold rolled sample, is eliminated by the final 800℃ annealing. As the thickness reduction rate of samples by rolling increases, the saturation magnetization and the remanence increase with x-ray diffraction line shift and are related with the rolling direction. On the other hand, the coercivity decreases at a critical thickness reduction rate of 65%. As the heat treatment temperature increases, the remanence and coercivity decrease with line width but saturation magnetization is maintained at approximately a constant value that has nothing to do with heat treatment. This means that a domain wall motion is easy owing to elimination of a residual stress formed parallel to the rolling direction owing to creation of the like-atom pairs across the slip plane by rolling.
Brillouin light scattering of CoFe/IrMn-based top and bottom spin-valves
Kyung-Hunn Han,조재훈,이석목,Jung Gi Kim 한국물리학회 2008 Current Applied Physics Vol.8 No.2
The spin-wave Brillouin light scattering (BLS) was observed from CoFe/IrMn-based bottom and top spin-valve structures. The mag-quency was simulated using a simple model which includes crystallographic, exchange, in-plane uniaxial, and in- and out-of-planeanisotropies and takes the exchange interaction between the two ferromagnetic layers into account. This enabled us to determine, in addi-tion to the other magnetic parameters, both in- and out-of-plane anisotropy constants near the surface. It was found that the top spin-valve is in a strong out-of-plane anisotropy whereas in-plane anisotropy is dominant for the bottom spin-valve.
Kyung Hunn Han,Jung Gi Kim,ukmock Lee,이영백 한국물리학회 2005 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.46 No.2
The magnetic properties of Au/Fe multilayer films prepared by dc sputtering have been investigated by using Brillouin light scattering. The thickness of the Fe layer is constant at 2 nm, while the thickness of the Au layer (dAu) varies from 1 to 3 nm. The magnetization per unit volume of Fe decreases with increasing dAu. The interlayer exchange coupling turns out to be antiferromagnetic for dAu 1.5 nm and ferromagnetic dAu > 1.5 nm. The interface anisotropy depends on the dAu and has a positive value.
Experimental Evidence for New Pinning Conditions in Strongly Pinned Permalloy Film
Kyung Hunn Han,Jae Hun Cho,Sukmock Lee 한국자기학회 2007 Journal of Magnetics Vol.12 No.1
Experimental evidence suggests that spin pinning conditions for standing spin mode in polycrystalline Ni?₄Fe₁? alloy film, is confirmed using the four categories of Camley et al. and the value of q⊥ for the pinning conditions, this was achieved by performing Brillouin light scattering measurements. The value of q⊥ was observed, in order to increase at a rate of π/2 with an increasing mode number. With this condition, the coexistence of standing spin wave modes was shown, with intermediate pinning, in addition to free and strong pinning. The values for spin-wave-stiffness constant (DB), g-factor (g), and surface magnetization (4 πM) of the Permalloy film were obtained from the results of BLS, and determined to be DB=1.85 ± 0.05 Oe㎠, g=2.11 ± 0.02, and 4 πM=8.7 kG, respectively.
Increment of the Exchange Coupling in Fe-Ni Alloy Thin Films Deposited with a Bias Magnetic Field
Kyung Hunn Han,Jung Gi Kim,Jae Hun Cho,Sukmock Lee 한국자기학회 2006 Journal of Magnetics Vol.11 No.2
The structure and magnetic properties of Fe-Ni films, deposited by DC magnetron sputtering on Si(111) wafer, have been studied. The spin wave stiffness constant is determined by Brillouin light scattering (BLS) and compared with the value obtained from magnetization measurements. The range of exchange interaction was determined as 0.4 atomic distances in the film deposited in a bias magnetic field, which is 1/2 that in the film grown in no bias magnetic field. The results show that the dimensions of exchange coupling increased by the sputtering in the magnetic field.
고에너지 볼밀링 방법에 의한 분말 Mn/Fe₂O₃의 자기상특성
김정기,한경훈,장지영,김현중 漢陽大學校 自然科學硏究所 2003 自然科學論文集 Vol.23 No.-
고에너지 볼밀링 방법과 연속적인 열처리 과정을 통해 합성된 Mn/Fe₂O₃의 구조적, 자기적 특성을 x선 회절기, FE-SEM, 진동 시료 자력계와 Mo¨ssbauer 분광기를 이용하여 연구하였다. 밀링 후와 500℃ 열처리 후 시료의 x선 회절피크는 헤마타이트 상이 우세하였으며, 900℃ 열처리 후 시료는 Mn₂O₃와 Fe₂O₃상이 공존함을 보였다. 또한 MnFe₂O₄나노 결정 스피넬 페라이트 상이 1200℃ 열처리 후에 나타났으며, grain size는34nm로 측정되었다. Mn 페라이트의 자화값과 보자력은 각각 63 emu/g 와 30 Oe였다. 고에너지 볼밀링과 연속적인 열처리 과정을 통해 형성된 자기상은 상온에서의 Mo¨ssbauer 스펙트럼으로 관찰되었다. The crystallography and magnetic properties of Mn/Fe₂O₃ powder synthesized by high-energy ball milling(HEBM) and subsequent heat treatment have been studied by the methods of x-ray diffraction (XRD), field emission scanning electron microscope (FE-SEM), vibrating sample magnetometer(VSM), and Mssbauer spectroscopy at room temperature. After as-milled and annealing at 500℃, the XRD patterns of the samples showed the broaden x-ray diffraction peaks corresponding to hematite phase. After annealing at 900℃, the phases of Mn₂O₃ and Fe₂O₃ were formed. A nanocrystalline spinel ferrite phases, MnFe₂O₄, was formed after annealing at 1200℃. The grain size was and determined to be 34 nm. The magnetization and coercivity of Mn ferrite at room temperature are 63 emu/g and 30 Oe, respectively. The magnetic phases obtained by HEBM and subsequent heat treatment were investigated by the means of Mssbauer spectrum.