• 제목/요약/키워드: magnetocrystalline anisotropy

검색결과 62건 처리시간 0.034초

Giant Perpendicular Magnetic Anisotropy of a Fe(001) Surface: A Density Functional Study

  • Odkhuu, D.;Rhim, S.H.;Yun, Won Seok;Hong, S.C.
    • 한국자기학회:학술대회 개요집
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    • 한국자기학회 2013년도 자성 및 자성재료 국제학술대회
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    • pp.29-29
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    • 2013
  • We predict agigantic perpendicular magnetocrystalline anisotropy (MCA) in Fe (001) capped by 5d transition metal (TM) overlayers by using first principles calculations. Analysis of atom-by-atom contribution to MCA reveals that gigantic MCA as large as 11 meV/TM originates not from Fe atoms but from the 5d TMs through the strong spin-orbit coupling. More specifically, it is the hybridization between TM and Fe d orbitals that also induces non-negligible magnetic moments in TM. Furthermore, spin-channel decompositions of MCA matrix with and without the presence of Fe substrate identify the electronic origin of the perpendicular MCA that the down-down channel contribution plays the most crucial role for the sign changes of MCA of TM overlayers upon the hybridization with Fe-3d.

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화학기상응축(Chemical Vapor Condensation)공정으로 제조한 L10규칙상 Fe50Pt50 나노분말의 특성 (Characteristics of L10 Ordered Fe50Pt50 Nanoparticles Synthesized by Chemical Vapor Condensation Process)

  • 이경모;유지훈;이동원;김병기;김혁돈;장태석
    • 한국분말재료학회지
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    • 제14권5호
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    • pp.281-286
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    • 2007
  • Ordered $L1_0$ to FePt nanoparticles are strong candidates for high density magnetic data storage media because the $L1_0$ phase FePt has a very high magnetocrystalline anisotropy $(K_u{\sim}6.6-10{\times}10^7erg/cm^3)$, high coercivity and chemical stability. In this study, the ordered $L1_0$ FePt nanoparticles were successfully fabricated by chemical vapor condensation process without a post-annealing process which causes severe particle growth and agglomeration. The $Fe_{50}Pt_{50}$ nanopowder was obtained when the mixing ratio of Fe(acac) and Pt(arac) was 2.5 : 1. And the synthesized FePt nanoparticles were very fine and spherical shape with a narrow size distribution. The average particle size of the powder tended to increase from 5 nm to 10 nm with increasing reaction temperature from $800^{\circ}C$ to $1000^{\circ}C$. Characterisitcs of FePt nanopowder were investigated in terms of process parameters and microstructures.

체심정방정 구조 Fe-Co계 합금상의 합성 및 그 자기적 특성 (Synthesis and Magnetic Properties of Body-centered-tetragonal Fe-Co Alloy)

  • 김경민;권해웅;이정구;유지훈
    • 한국자기학회지
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    • 제27권4호
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    • pp.129-134
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    • 2017
  • 합금 제조에 흔히 이용되는 기존의 용해, 응고, 열처리 등의 가공 공정으로 덩치 형태의 체심정방정 구조의 Fe-Co계 합금상을 합성하고, 그 결정학적, 자기적 특성을 조사하였다. $(Fe_{100-x}Co_x)_{1-y}C_y$ 합금에서 체심정방정 구조의 단일상(martensite)이 얻어지는 Co 및 C의 함량은 크게 제한되어, Co의 함량 x = 2.5, C의 함량 y = 0.062로 제한된 조성에서 체심정방정 구조의 단일상 합금이 얻어졌다. 합성된 조성 $(Fe_{97.5}Co_{2.5})_{0.938}C_{0.062}$인 체심정방정 구조의 단일상 합금의 정방성(tetragonality, c/a)은 1.05였으며, 이 합금의 결정자기 이방성 상수, $K_1$ 값은 순수 철(${\alpha}-Fe$)의 $K_1$ 값에 비하면 3.1배 정도 높은 $1.5{\times}10^5J/m^3$였다.

준안정상 기반의 질화철계 영구자석소재 제조연구동향 (Research trend in Fabrication of Metastable-phase Iron Nitrides for Hard Magnetic Applications)

  • 김경민;이정구;김경태;백연경
    • 한국분말재료학회지
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    • 제26권2호
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    • pp.146-155
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    • 2019
  • Rare earth magnets are the strongest type of permanent magnets and are integral to the high tech industry, particularly in clean energies, such as electric vehicle motors and wind turbine generators. However, the cost of rare earth materials and the imbalance in supply and demand still remain big problems to solve for permanent magnet related industries. Thus, a magnet with abundant elements and moderate magnetic performance is required to replace rare-earth magnets. Recently, $a^{{\prime}{\prime}}-Fe_{16}N_2$ has attracted considerable attention as a promising candidate for next-generation non-rare-earth permanent magnets due to its gigantic magnetization (3.23 T). Also, metastable $a^{{\prime}{\prime}}-Fe_{16}N_2$ exhibits high tetragonality (c/a = 1.1) by interstitial introduction of N atoms, leading to a high magnetocrystalline anisotropy constant ($K_1=1.0MJ/m^3$). In addition, Fe has a large amount of reserves on the Earth compared to other magnetic materials, leading to low cost of raw materials and manufacturing for industrial production. In this paper, we review the synthetic methods of metastable $a^{{\prime}{\prime}}-Fe_{16}N_2$ with film, powder and bulk form and discuss the approaches to enhance magnetocrystalline anisotropy of $a^{{\prime}{\prime}}-Fe_{16}N_2$. Future research prospects are also offered with patent trends observed thus far.

$(Sm_{0.5}RE_{0.5})Fe_{11}Ti$ 화합물의 구조 및 자기특성 (Structure and Magnetic Properties of $(Sm_{0.5}RE_{0.5})Fe_{11}Ti$ Compounds)

  • 김희태;김윤배;김창석;김택기;권혁무
    • 한국자기학회지
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    • 제3권3호
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    • pp.196-200
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    • 1993
  • $(Sm_{0.5}RE_{0.5})Fe_{11}Ti$ 화합물(RE=Ce, Pr, Nd, Sm, Gd, Tb, Dy)은 정방정(tetragonal) $ThMn_{12}$ 형 구조로 형성되며 c축을 자화용이축으로하는 일축결정자기이방성을 갖 는다. 주조한 $(Sm_{0.5}RE_{0.5})Fe_{11}Ti$ 화합물은 RE=Sm일 때 가장 높은 이방성자장 11200 kA/m(140 kOe)을 가지며, RE=Nd일 때 포화자화가 $122.3\;Am^{2}/kg$(122.3 emu/g)로 가장 크며, RE=Gd일 때 큐리온도가 $326^{\circ}C$로 가장 높다.

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The Modified Magnetic Properties of $Mn_3Ga$ Ferrimagnet by Stabilizing on GaSb (001)

  • Feng, Wuwei;Dung, Dang Duc;Cho, Sung-Lae
    • 한국자기학회:학술대회 개요집
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    • 한국자기학회 2009년도 정기총회 및 동계학술연구발표회
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    • pp.203-203
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    • 2009
  • We report on the epitaxial growth of tetragonal $DO_{22}$-type Mn3Ga films on GaSb (001) using molecular beam epitaxy and the related structural and magnetic properties. The as-studied $Mn_3Ga$ film was found to exhibit relatively small coercivity around 400 Oe, which differs greatly from the hard magnetic properties of $Mn_3Ga$ bulk specimen or films that are normally reported. This difference was probably attributed to the effects of the GaSb (001) substrate that forced the $Mn_3Ga$ film to be two-dimensionlly stabilized in the (114) orientation and thus led to the modified intrinsic properties of $Mn_3Ga$ films. The growth orientation of the Mn3Ga (114)//GaSb (001) also caused the easy magnetocrystalline direction located in the film plane due to the dominant shape anisotropy in the thin films.

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블록 공중합체를 이용한 CoCrPt 나노점 배열의 자기적 성질 연구 (MAGNETIC PROPERTIES OF CoCrPt NANODOTS ARRAY MADE BY PS-PMMA BLOCK COPOLYMER TEMPLATE)

  • Jeong, Jong-Ryul;Im, Mi-Young;Shin, Sung-Chul;Park, Dae-Geun;Kwon, Ki-Young;Jung, Hee-Tae;Yang, Seung-Man
    • 한국자기학회:학술대회 개요집
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    • 한국자기학회 2002년도 동계연구발표회 논문개요집
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    • pp.34-35
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    • 2002
  • CoCrPt alloy films are attracting wide attention for applications to high-density magnetic recording media and hard magnetic layer in spin valve structure due to their high coercivity and strong magnetocrystalline anisotropy. Diblock copolymer templates are one of the most promising candidates for nanoscale patterning otherwise inaccessible by lithographic procedures [1]. In this study, we have investigated magnetic properties of Co$\sub$68/Cr$\sub$18/Pt$\sub$14/ nanodot arrays made by self-assembling polystyrene-block-methyl methacrylate ((PS-b-PMMA), (Mn = 82.5 Kg/mol, with a 1.12 polydispersity)) diblock copolymer. (omitted)

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