• Journal of Magnetics
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• 제18권4호
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• pp.405-411
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• 2013

The structural, magnetic and magnetocaloric properties of $CoMn_{1-x}Cr_xGe$ (x=0.05-0.125) have been investigated by using electron microscopy, x-ray diffraction, calorimetric and magnetic measurements. In this study, our aim is to justify the magnetocaloric effect by tuning the structural and magnetic transition temperature with Cr doping on CoMnGe pure system. The substitution of Cr for Mn leads to a decrease of both structural and magnetic transition temperatures. However, structural and magnetic transition temperatures do not close to each other. From magnetization measurement, we calculate that isothermal entropy change associated with magnetic transition can be as high as 3.82 J $kg^{-1}K^{-1}$ at 302 K in a field of 7 T. Meanwhile, structural phase transition contribution to isothermal entropy change is calculated as 5.85 J $kg^{-1}K^{-1}$ at 322 K for 7 T.

• 한국자기학회지
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• 제8권6호
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• pp.350-356
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• 1998

Sol-gel법을 이용하여 합성한 자성 garnet Y3-xLaxFe5O12(x=0.0, 0.25, 0.5, 0.75, 1.0) 분말과 박막의 결정 및 자기적 성질에 관하여 X-선 회절기, atomic force microscopy(AFM), scanning electron microscopy(SEM), 진동시료자화기 (VSM)와 Mossbauer 부노강기를 이용하여 연구하엿다. X-선 회절분석 결과와 Mossbauerqnsrhkd 실험으로부터 100$0^{\circ}C$에서 열처리한 x=0.75 이하의 Y3-xLaxFe5O12 분말의 경우 모두 순수한 cubic의 garnet 구조가 형성되었음을 확인 할 수 있었으나, x=1.0인 경우는 LaFeO3상이 함께 관측되었다. Garnet 박막의 성장을 위하여 75$0^{\circ}C$에서 2시간의 열처리로 결정화를 이루었으며, 성장한 박막은 특정한 방향성 없이 성장하였음을 알 수 있었다. Mossbauer 분광기를 이용하여 측정한 결과는 산화물을 통하여 제조한 garnet 분말의 Mossbauer spectrumthk 일치함을 알 수 있었다. 전자 현미경의 측정을 통한 분말의 입자크기는 200~300nm이며, AFM의 측정으로부터 박막의 평균 표면 거칠기가 3.17nm임을 알 수 있었다. 진동시료자화기를 이용하여 측정한 garnet 분말과 박막의 자기적 특성은 전형적인 연자성의 자기적 속성을 가지며, garnet 분말의 경우 최대 포화자화 (30 emu/g)와 최소 보자력 (52 Oe)을 가짐을 알 수 있엇다. 80$0^{\circ}C$에서 열처리한 순수한 garnet 박막시료의 경우 수직 및 수평방향으로 측정한 자화곡선은 수직방향으로 측정한 자화곡선이 낮은 포화자화를 가지며 보자력은 양방향 모두 37 Oe를 나타냈다.

• Journal of Magnetics
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• 제16권4호
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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.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2000년도 추계학술대회 논문집
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• pp.459-462
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• 2000

A new method for the fabrication of poly-Si films is reported using by alternating magnetic flux crystallization (AMFC) of LPCVD a-Si films. In this work we have studied the crystallization of LPCVD a-Si films by alternating magnetic flux. A-Si films were 1200$\AA$-thick deposited at 48$0^{\circ}C$ at a total pressure of 0.25Torr using Si$_2$H$_{6}$/H$_2$. After this step, these a-Si films were thermally annealed by Alternating Magnetic Flux at 43$0^{\circ}C$ for 1hours. The annealed films were characterized using X-ray diffraction (XRD), Raman Spectra, Atomic Force Microscopy(AFM). Both alternating magnetic flux crystallization and solid phase crystallization were investigated to compare enhanced crystallization a-Si. We have found that the low temperature crystallization method at 43$0^{\circ}C$ by alternating magnetic flux.x.

• Journal of Magnetics
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• 제18권1호
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• pp.26-29
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• 2013

$Mn_xFe_{3-x}O_4$ powders have been fabricated by using sol-gel methods; their crystallographic and magnetic properties were investigated by using X-ray diffraction, scanning electron microscopy, M$\ddot{o}$ssbauer spectroscopy, and vibrating sample magnetometer. The $Mn_xFe_{3-x}O_4$ ferrite powders annealed at $500^{\circ}C$ had a single spinel structure regardless of the $Mn^{2+}$-doping amount and their lattice constants became larger as the $Mn^{2+}$ concentration was increased. Their Mossbauer spectra measured at room temperature were fitted with 2 Zeeman sextets due to the tetrahedral and octahedral sites of Fe ions, which made them ferrimagnetic. The magnetic behavior of $Mn_xFe_{3-x}O_4$ powders showed that the $Mn^{2+}$-doping amount made their saturation magnetization increase, but there were no severe effects on their coercivities. The saturation magnetization of the $Mn_xFe_{3-x}O_4$ powder varied from 38 emu/g to 70.0 emu/g and their minimum coercivity was 111.1 Oe.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 1988년도 추계학술대회 논문집
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• pp.46-46
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• 1988

Structural and magnetic properties of Co-Cr-Mo films were investigated in connection with sputtering conditions. Films were prepared using a convention RF sputtering system. X-ray diffractometry, scanning electron microscopy and transmission electron microscopy were employed to investigate structure properties. Vibrating sample magnetometry was used for coercivity and saturation magnetization measurements. Co-Cr-Mo films displayed reasonable values of perpendicular coercivity and saturation magnetization for perpendicular recording media and showed good perpendicular orientation of the hcp c-axis to the film surface. Perpendicular coercivity was strongly dependent upon substrate technique showed better c-axis orientation than hose using the stationary substrate. Co-Cr-Mo films of 2.9 at. % Mo content showed maximum perpendicular coercivity and saturation magnetization. The films deposited at lower Ar pressure showed good magnetic properties. There was no explicit relationship between the columnar structure and c-axis orientation. Co-Cr-Mo films was found to have suitable structural and magnetic properties for perpendicular recording media.

• Journal of Magnetics
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• 제18권4호
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• pp.391-394
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• 2013

In this study, nickel-zinc ferrite nanoparticles, with the chemical formula of $Ni_{0.3}Zn_{0.7-x}Cu_xFe_2O_4$ (where x = 0.1- 0.6 by step 0.1), were fabricated by the sol-gel method. The effect of copper substitution on the phase formation and crystal structure of the sample was investigated by X-ray diffraction (XRD), thermo-gravimetry (TG), differential thermal analysis (DTA), Fourier transform infrared spectrometry (FT-IR), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The XRD result shows that due to the reduction of Zn content,the crystallite size of the sample increased. The results of the vibration sample magnetometer (VSM) exhibit an increase in saturation magnetization value (Ms) for samples with x ${\leq}$ 0.3 and a linear decrease for samples with x > 0.3. The variation of saturation magnetization and coercivity of the samples were then studied.

• 한국재료학회지
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• 제31권12호
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• pp.690-696
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• 2021

The purpose of this study is to develop a zirconium-based alloy with low modulus and magnetic susceptibility to prevent the stress-shielding effect and the generation of artifacts. Zr-7Cu-xSn (x = 1, 5, 10, 15 mass%) alloys are prepared by an arc melting process. Microstructure characterization is performed by microscopy and X-ray diffraction. Mechanical properties are evaluated using micro Vickers hardness and compression test. The magnetic susceptibility is evaluated using a SQUID-VSM. The average magnetic susceptibility value of the Zr-7Cu-xSn alloy is 1.176 × 10^-8 cm³g^-1. Corrosion tests of zirconium-based alloys are conducted through polarization test. The average Icorr value of the Zr-7Cu-xSn alloy is 0.1912 ㎂/cm². The elastic modulus value of 14 ~ 18 GPa of the zirconium-based alloy is very similar to the elastic modulus value of 15 ~ 30 GPa of the human bone. Consequently, the Sn added zirconium alloy, Zr-7Cu-xSn, is very interesting and attractive as a biomaterial that reduces the stress-shielding effect caused by differences of elastic modulus between human bone and metallic implants. In addition, this material has the potential to be used in metallic dental implants to effectively eliminate artifacts in MRI images due to low magnetic susceptibility.

• 한국세라믹학회지
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• 제40권1호
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• pp.62-68
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• 2003

졸-겔법으로 보자력 제어에 뛰어난 첨가제인 Co와 Ti을 첨가한 Ba-ferrite 미립자를 합성하였다. 졸-겔 반응시, 반응 시간이 90분에서 120분 이내에서 온도, pH 및 점도의 변화가 없고, aging 시간에 따라 점도가 안정한 상태치 졸을 얻을 수 있었다. 이 졸을 건조 및 열처리 후, Differential Thermal Analysis(DTA)와 X-Ray Diffractometer(XRD)를 통해 Ba-ferrite 상이 약 $700^{\circ}C$부터 생성됨을 확인하였으며, 열처리 온도 증가에 의해 결정성이 좋아짐을 볼 수 있었다. Scanning Election Microscopy(SEM)로 표면형상을 관찰한 결과 열처리 온도가 증가함에 따라 입자크기가 증가하였으며, 비교적 균질한 입도 분포의 미립자를 얻을 수 있었다. 또한, Vibrating Sample Magnetometer(VSM)로 Co와 Ti의 첨가량에 따른 자기적 특성을 관찰하였으며, 포화자화(M$_{s}$ )값은 첨가량에 관계없이 변화가 없었으나, 보자력(H$_{c}$)값은 첨가량에 따라 크게 변화하였다.

• 한국자기학회:학술대회 개요집
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• 한국자기학회 2010년도 임시총회 및 하계학술연구발표회
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• pp.114-115
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• 2010