• Proceedings of the Materials Research Society of Korea Conference
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• 2011.05a
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• pp.240.1-240.1
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• 2011

본 연구에서는 펄스레이져 박막 증착법(Pulsed Laser Deposition;PLD)을 이용하여 연자성의 CoNiFe (CNF) 물질과 강유전 특성의$BaTiO_3$ (BTO) 물질을 다층박막 구조로 제작하여 약자장(H=200 Oe)에 의해 에너지를 집적 시키거나 유전상수를 조절하여 박막의 구조 변화에 따른 커패시턴스 변화를 연구하였다. 다양한 구조의 다층 박막은 Si/$SiO_2$/Ti/Pt(111) 기판상에 PLD을 이용하여 증착하였으며, Phillp's X-선 회절기 (XRD)를 이용하여 결정구조와 격자 상수를 결정하였다. FE-SEM, TEM, AFM 및 EDS를 이용하여 박막 표면/단면의 미세구조 및 물질에 따른 조성비를 확인하였다. 자기적 특성을 위해Vibrating Sample Magnetometer (VSM)를 측정하였고, 전기적 특성은 LCR meter를 이용하여 측정하였다.

• Nuclear Engineering and Technology
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• v.52 no.3
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• pp.610-613
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• 2020

Specimens of austenitic stainless steel were irradiated with 6 MeV Xe ions to two doses of 7 and 15 dpa at room temperature and 300 ℃ respectively. Then partial irradiated specimens were subsequently thermally annealed at 550 ℃. Irradiation-induced BCC-phase formation and magnetism were analyzed by grazing incidence X-ray diffraction (GIXRD) and vibrating sample magnetometer (VSM). It has been shown that irradiation damage level, irradiation temperature and annealing temperature have significant effect on BCC-phase formation. This BCC-phase changes the magnetic behavior of austenitic stainless steel. The stress relief and compositional changes in matrix are the driving forces for BCC-phase formation in austenitic stainless steel during ion irradiation.

• Journal of Magnetics
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• v.20 no.3
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• pp.207-210
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• 2015

Modifications in the structural and magnetic properties of co-precipitated cobalt ferrite nanoparticles can be accomplished by varying the annealing time periods during the synthetic process. Experimental results show that high-purity cobalt ferrite nanoparticles are obtained using a co-precipitation process. The dependence of the crystallite sizes on the annealing time was successfully demonstrated using XRD and SEM. Finally, vibrating sample magnetometer analyses show that the magnetic properties of the cobalt ferrite nanoparticles depend on their relative particle sizes.

• Journal of Magnetics
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• v.20 no.3
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• pp.241-245
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• 2015

A study on the preparation of nickel oxide nanoparticles using electron beam irradiation is described. Nickel nanoparticles were synthesized with nickel chloride hexahydrate as a metal precursor and different sodium hydroxide concentrations using electron beam irradiation. The effects of sodium hydroxide concentration and electron beam absorbed doses were investigated. The samples were synthesized at different sodium hydroxide concentrations and with absorbed doses of 100 to 500 kGy at room temperature. Synthesized nanoparticles were characterized by X-ray diffraction (XRD) and field emission scanning electron microscopy (FE-SEM) and a vibrating sample magnetometer (VSM). The nanoparticle morphologies seemed to be non-spherical and aggregated. The 1:1 molar ratio of nickel chloride hexahydrate and sodium hydroxide showed a higher purity and saturation magnetization value of 13.0 emu/g. The electron beam absorbed dose was increased with increasing nickel nanoparticle nucleation.

• Journal of Environmental Science International
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• v.12 no.1
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• pp.41-45
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• 2003

Magnetite powder for kerosene-based ferrofluid was synthesized by air oxidation of waste acid containing $Fe^{2+}$ and $Fe^{3+}$ ions in the pH=11 at $60^{\circ}C$. Stable kerosen-based ferrofluid was prepared by addition of polyoxyethylene nonylphenyl ether(POENPE) to the magnetite containing water. Dispersion mechanism of an addition POENPE to the magnetite was examined by means of the fraction of solid dispersed FT-IR spectrum. And magnetic properties of kerosen-based ferrofluid were examined by method of Vibrating Sample Magnetometer. In order to remove oil on the water surface by an addition of kerosen-based ferrofluid, the optimum conditions were examined.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 1992.11a
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• pp.7-10
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• 1992

CoNiCr/Cr and CoCrTa/Cr for longitudinal magnetic recording media were. prepared on Coming 7059 glass by RF magnetron sputtering. The thickness of Cr underlayer was varied from 500 to $3000{\AA}$ and. that of magnetic layer was $700{\AA}$. Coercivity and squareness were measured using V.S.M.(vibrating sample magnetometer). The coercivity of films increased with increasing Cr thickness when the films were unannealed. The coercivity of the films annealed in a 10 mtorr vacuum increased initially with annealing time and then saturated with further increase in annealing time. The coercivity value difference between the unannealed and annealed films increased with increasing the thickness of Cr underlayer No significant change was found in squareness after anneal, regardless of Cr underlayer thickness.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.14 no.3
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• pp.257-262
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• 2001

Single crystalline films of La doped YIG(yttrium iron garnet) were grown by the liquid phase epitaxy. The lattice constants of films obtained by DCD(double crystalline diffractometer) measurement increased with increasing La contents in films. In particular, lattice constants of films grown wiht Y/La=20 solution were nearly same as those of GGG (gadolinium gallium garnet) substrate. The saturation magnetization measured with VSM (vibrating sample magnetometer) was about 1750Gauss which is the same as that of pure YIG irrespective of La contents in films. FMR(ferromagnetic resonance) linewidth of La doped YIG was smaller than that of pure YIG. Since appropriate La doping decreases the lattice mismatch between film and substrate, the FMR linewidth was Y/La=20 in this experiment.

• Journal of Magnetics
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• v.16 no.4
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• pp.413-416
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• 2011

An array of FeCo nanotubes has been successfully fabricated in the pores of porous anodic aluminum oxide (AAO) templates by wetting templates method. The morphology and structure of the nanotube array were characterized by scanning electron microscopy, transmission electron microscopy and x-ray diffraction. The average diameter of the nanotubes was about 200 nm, and the length was more than 10 ${\mu}m$. Vibrating sample magnetometer and superconducting quantum interference device were used to investigate the magnetic properties of the nanotube array. Interaction between the nanotubes has been found to be demagnetizing as expected and the switching field distribution is broad.

• Journal of Magnetics
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• v.2 no.2
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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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• v.21 no.1
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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.