• 대한화학회지
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• 제58권1호
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• pp.100-104
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• 2014

Magnetite nanoparticles were prepared by co-precipitation method and then silica was coated onto the surface of $Fe_3O_4$ by hydrolysis of TEOS. The silica coated magnetite nanoparticles were characterized for its structural, microstructural, optical, vibrational and magnetic properties by X-ray diffraction analysis, Scanning electron microscopy, UV-visible spectroscopy, Infrared spectroscopy and Vibration sample magnetometer, respectively. XRD study confirmed the presence of $SiO_2$ on the surface of magnetite nanoparticles. SEM study indicated that with increase in TEOS content the particles become bigger and mono-disperse. It was also found that the silica coating prevents magnetic particles from aggregation and imparts excellent stability.

• 한국자기학회지
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• 제11권1호
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• pp.32-37
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• 2001

건축물내 바닥면에서의 지자기장 분포에 대한 모사실험과 측정을 통하여 철골이 지자기의 분포에 미치는 영향을 연구하였다. 지자기 분포에 대한 모사시험은 유한요소법으로 수행하였으며, 바닥면에서 지자기장의 수직분력(Z)은 플럭스 게이트형 마그네토미터로 측정하였다. 수평으로 배열된 철골은 지자기장의 Z성분 분포에 미치는 영향이 비교적 적으나, 수직으로 배열된 철골은 토의 분포에 강한 영향을 주어 국소 지자기 교란을 일으킨다. 이러한 국소 지자기 교란은 연자성체로 이루어진 바닥이나 우회로 구조를 가지는 연자성체 바닥으로 완화된다.

• 한국자기학회지
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• 제10권6호
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• pp.302-309
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• 2000

박강판의 내부에 존재하는 개재물성 결함을 검사하기 위해 누설자속법을 이용하여 탐상하는 시스템을 개발하였다. 연자성 코어의 보자력을 이용한 차등형 플럭스게이트 자력계를 제작하였다. FEM 소프트웨어를 이용하여 전자석을 설계하였으며, 3축 이동이 가능한 누설자속탐상장치를 제작하여 냉연강판을 검사한 결과 개재물성 결함을 검사학 수 있음을 알았다. 누설자속값을 디지털화하여 2차원 이미지로 처리한 결과 냉연강판에 존재하는 개재물성 결함 이외의 결함을 일부 구분할 수 있음을 알았다.

• Journal of Magnetics
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• 제2권2호
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• pp.38-41
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• 1997

Spinel ferrite thin films Fe3-x MnxO4 (x=0.000, 0.006, 0.0010, 0.015, 0.023) were prepared on the coverglass by ferrite plating technique. To investigate the uniaxial anisotrpy of the samples, the saturation and effective magnetization of the thin films were measured by VSM(vibrating sample magnetometer) and FMR(ferromagnetic resonance) measurements respectively. The spectroscopic splitting g factor were estimated from the ferromagnetic resonance curves. For x=0.000, 0.006, the effective magnetization was measured of temperatures form T=77 K to T=300 K. The results were analyzed in terms of Bloch's law Ms(T) = Ms(0) (1-BT3/2-CT5/2). The Bloch coefficient B, C were determined by fitting. Ms(0) was obtained by extrapolating Meff to 0 K. From this result, the spin wave stiffness constants D was also determined.

• Journal of Magnetics
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• 제21권1호
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• pp.29-34
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• 2016

Nd-doped $BiFeO_3$ materials were synthesized via a sol-gel method. The crystal structure, magnetic properties, and complex impedance spectroscopy of multiferroic $Bi_{1-x}Nd_xFeO_3$ (BNFO) materials were investigated by X-ray diffraction (XRD), Raman scattering, vibrating sample magnetometer (VSM), and complex impedance spectroscopy. Our results show that the lattice crystal constants (a, c) and the ratio c/a of BNFO materials decreased with increasing Nd concentration. All samples exhibited weak ferromagnetism at room temperature, and the magnetization of samples was enhanced by the presence of $Nd^{3+}$ ions. There was an enhancement in the spontaneous magnetization of BFO with increasing Nd concentration, which is attributable to the collapse of the spin cycloid structure.

• 한국소성가공학회:학술대회논문집
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• 한국소성가공학회 2009년도 춘계학술대회 논문집
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• pp.432-434
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• 2009

Metal nano-wire arrays on Cu-coated seed layers were fabricated by aqueous solution method using sulfate bath at room temperature. The seed layers were coated on Anodic aluminum oxide (AAO) bottom substrates by electrochemical deposition technique, length and diameter of metal nano-wires were dominated by controlling the deposition parameters, such as deposition potential and time, electrolyte temperature. Anodic aluminum oxide (AAO) was used as a template to prepare highly ordered Ni, Fe, Co and Cu multilayer magnetic nano-wire arrays. This template was fabricated with two-step anodizing method, using dissimilar solutions for Al anodizing. The pore of anodic aluminum oxide templates were perfectly hexagonal arranged pore domains. The ordered Ni, Fe, Co and Cu systems nano-wire arrays were characterized by Field Emission Scanning Electron Microscopy (FE-SEM) and Vibrating Sample Magnetometer (VSM). The ordered Ni, Fe, Co and Cu systems nano-wires had different preferred orientation. In addition, these nano-wires showed different magnetization properties under the electrodepositing conditions.

• 한국세라믹학회지
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• 제46권5호
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• pp.525-527
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• 2009

This paper presents a study on the magnetic behaviour of selected doped SiAlONs with various compositions including Y, Yb, Sm, Gd, and Er. The resulting crystalline phases were confirmed by X-ray diffraction. The magnetic hysteresis data for the samples were collected at room temperature using a vibrating sample magnetometer. The study revealed that doped SiAlONs experience an appreciable level of magnetic hysteresis. Although the parameters corresponding to hysteresis loops in doped SiAlONs are less than those of common ferrites, their magnetic properties of SiAlONs may open up new potential areas of application as the host SiAlON ceramics have excellent structural properties.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 1999년도 춘계학술대회 논문집
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• pp.578-581
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• 1999

The Co-Cr-Ta films are one of the most suitable candidates for perpendicular magnetic recording media. The facing targets sputtering(FTS) system has a advantage of preparing films over a wide range of working gas pressure on plasma-free substrates. In this study, we investigated the effect underlayers on the growths layers of Co-Cr-Ta recording layers. The Co-Cr-Ta/Ti(CoCr) double layers were deposited with sputter gas pressure$(P_N, 0.3-1mTorr)$ by using FTS apparatus at temperature of$40^{\circ}C~-300^{\circ}C$, respectively. Crystallographic and magnetic characteristics were evaluated by x-ray diffractometry(XRD) and vibrating sample magnetometer(VSM), respectively.

• Journal of Magnetics
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• 제12권3호
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• pp.108-112
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• 2007

Nature of phase transition in $LaVO_3$ has been studied using X-ray diffraction, SQUID magnetometer, and $M\"{o}ssbauer$ spectroscopy with 1% of $^{57}Fe$ doped sample. The crystal structure was orthorhombic with space group Pnma. Antiferromagnetic phase transition temperature $T_N$ was 140K, below which a weak ferromagnetic trace has been found. $M\"{o}ssbauer$ spectra below $T_N$ were single set of hyperfine sextet, which enabled us to discard the possibility of two inequivalent magnetic sites or uncompensated antiferromagnetism. Hyperfine magnetic field abruptly disappeared as low as about 90K, much below $T_N$.

• Journal of Magnetics
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• 제4권4호
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• pp.115-118
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• 1999

$MgFe_2O_4$ has been studied with X-ray diffraction, M ssbauer spectroscopy and vibration sample magnetometer (VSM). The crystal structure of the sample is found to have a cubic spinel structure with a lattice constant of $a_0=8.390$\pm$0.005$\AA$.$ The iron ions at both A (tetrahedral) and B (octahedral)sites are found to be in ferric high-spin states. Its Neel temperature TN is found to be 710$\pm$3 K. The Debye temperature for the A and B sites found to be 417$\pm$5 K and 331$\pm$5 K., respectively. Atomic migation from the A to the B sites starts near 425 K and increases rapidly with increasing temperature to such a degree that 31% of the ferric ions at the A sites have moved over to the B sites by 600 K.