• Title/Summary/Keyword: magnetic oxide

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Effect of Insertion of Hf layer in Al oxide tunnel barrier on the properties of magnetic tunnel junctions (알루미늄 산화물 절연막에 하프늄의 첨가가 자기터널접합의 특성에 미치는 영향)

  • Lim, W.C.;Bae, J.Y.;Lee, T.D.;Park, B.G.
    • Journal of the Korean Magnetics Society
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    • v.14 no.1
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    • pp.13-17
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    • 2004
  • We have investigated the effect of Hf insertion in the Al oxide tunnel barrier on the properties of magnetic tunnel junctions (MTJs). MTJs with Hf inserted barrier show the higher tunnel magnetoresistance (TMR) ratio and less temperature and bias voltage dependence of TMR than MTJs with a conventional Al$_2$O$_3$ barrier. The enhancement of TMR ratio and the reduction of the temperature and bias voltage dependence might be due to the reduction of defects in the barrier. Al-Hf oxide was formed by depositing Al and Hf simultaneously, and oxidizing the compound films. The TMR ratio of 36% was almost the same value as that with Hf inserted barrier. This implies that the inserted Hf layers mixed with Al layers during deposition or oxidation, and they might form Al Hf oxide barriers. This compound Al Hf oxide formation may be responsible to reduction of defect concentration which enhanced the TMR ratio and reduced temperature and bias-voltage dependence.

Magnetic Properties of NiZn-ferrite Synthesized from Waste Iron Oxide Catalyst (산화철 폐촉매로부터 합성된 NiZn- 페라이트의 자기적 특성)

  • Hwang, Yeon;Kwon, Soon-Kil;Lee, Hyo-Sook;Je, Hae-June;Park, Sang-Il
    • Journal of the Korean Ceramic Society
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    • v.38 no.12
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    • pp.1162-1166
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    • 2001
  • NiZn-ferrite was synthesized from waste catalysts, which were produced from styrene monomer process and buried underground as an industrial wastes, and its magnetic properties were investigated. Nickel oxide and zinc oxide powders were mixed with finely ground waste catalysts, and spinel type ferrite was obtained by calcination at 900$\^{C}$ and sintering at 1230$\^{C}$ for 5 hours. The intial permeability was measured and reflection loss was calculated from S-parameters for the composition of Ni$\_$x/Zn$\_$1-x/Fe$_2$O$_4$(x=0.36, 0.50, 0.66). NiZn-ferrite synthesized from waste iron oxide catalyst showed a feasibility for the use as electromagnetic wave absorber in X-band.

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Relationship between Physicochemical Properties, Heavy Metal Contents and Magnetic Susceptibility of Soils (토양의 물리화학적 특성, 중금속 함량, 대자율 간의 상호관계 연구)

  • Chon, Chul-Min;Park, Jeong-Sik;Kim, Jae-Gon;Lee, Youn-Soo
    • Journal of the Mineralogical Society of Korea
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    • v.23 no.4
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    • pp.281-295
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    • 2010
  • This paper deals with magnetic susceptibility, mineralogy, soil properties (pH, EC, CEC, loss on ignition), iron and manganese oxides, the content and partitioning of heavy metals (As, Cd, Cr, Cu, Ni, Pb, Zn), and their mutual relationship in the soil samples of an unpolluted, abandoned mine area, and industrial complex area. The various minerals derived from weathered bedrock were identified by X-ray diffraction in the unpolluted soil samples, except for the magnetic minerals. XRD analysis also revealed the existence of hematite and magnetite related to mine tailings and waste rocks in the abandoned mine area samples. The industrial complex area samples had carbonate minerals, such as calcite and dolomite, that might be due to anthropogenic deposition. The sum of the reducible, oxidizable, and residual fractions was over 80% for the abandoned mine area samples and over 50% for the industrial complex area samples using the sequential extraction method. The industrial complex area samples had a relatively high carbonate fraction that was associated with carbonate minerals. The content of aqua regia-extractable Fe, Mn, As, and Zn had a high positive correlation with the content of the dithionite-citrate-bicarbonate (DCB)-extractable method related to Fe/Mn oxide phases. The 54% and 58% of aqua regia-extractable Fe and As content, respectively, acted together with the concentrations of the DCB-extractable phases. Magnetic susceptibility values of total samples ranged from 0.005 to $2.131{\times}10^{-6}m^3kg^{-1}$. The samples including iron oxide minerals, such as hematite and magnetite, had a high magnetic susceptibility. The magnetic susceptibility showed a significant correlation with the heavy metals, Cd (r=0.544, p<0.05), Cr (r=0.714, p<0.01), Ni (r=0.645, p<0.05), Pb (r=0.703, p<0.01), and Zn (r=0.496, p<0.01), as well as Fe (r=0.608, p<0.01) and Mn (r=0.615, p<0.01). The aqua regia-extractable Fe and Mn content had a significant positive correlation with Cd, Cr, Cu, Ni, and Zn. However, the DCB-extractable Fe and Mn content had a significant positive correlation with As and Ni, indicating that the heavy metals were associated with Fe and Mn oxide minerals.