• 제목/요약/키워드: spin-dependent

검색결과 171건 처리시간 0.035초

MBE-growth and Oxygen Pressure Dependent Electrical and Magnetic Properties of Fe3O4 Thin Films

  • ;;신유리미;;조성래
    • 한국진공학회:학술대회논문집
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    • 한국진공학회 2011년도 제40회 동계학술대회 초록집
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    • pp.60-60
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    • 2011

  • Giant magnetoresistance (GMR), tunneling magnetoresistance (TMR), and magnetic random-access memory (MRAM) are currently active research areas in spintronics. The high magnetoresistance and the high spin polarization (P) of electrons in the ferromagnetic electrodes of tunnel junction or intermediate layers are required. Magnetite, Fe3O4, is predicted to possess as half-metallic nature, P ~ 100% spin polarization, and has a high Curie temperature (TC~850 K). Experiments demonstrated that the P~($80{\pm}5$)%, ~($60{\pm}5$)%, and ~40-55% for epitaxial (111), (110) and (001)-oriented Fe3O4 thin films, respectively. Epitaxial Fe3O4 films may enable us to investigate the effects of half metals on the spin transport without grain-boundary scattering.In addition, it has been reported that the Verwey transition (TV, a first order metal-insulator transition) of 120 K in bulk Fe3O4 is strongly affected by many parameters such as stoichiometry and stress, etc. Here we report that the growth modes, magnetism and transport properties of Fe3O4 thin films were strongly dependent on the oxygen pressure during film growth. The average roughness decreases from 1.021 to 0.263 nm for the oxygen pressure increase from $2.3{\times}10-7$ to $8.2{\times}10^{-6}$ Torr, respectively. The 120 K Verwey transition in Fe3O4 was disappeared for the sample grown under high oxygen pressure.

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Investigation of Spin Reorientation in Ga Substituted Y-type Hexaferrite based on Mössbauer Spectroscopy

  • Lim, Jung Tae;Kim, Jeonghun;Kim, Chul Sung
    • Journal of the Korean Physical Society
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    • 제73권11호
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    • pp.1708-1711
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    • 2018

  • The polycrystalline sample of $Ba_2Co_{1.5}Mg_{0.5}Fe_{11.88}Ga_{0.12}O_{22}$ Y-type hexaferrite, doped with Ga-cation, was prepared by using the solid-state reaction method. The crystalline structure of sample was investigated by x-ray diffractometer (XRD), and the magnetic properties of sample were measured by vibrating sample magnetometer (VSM), and $M{\ddot{o}}ssbauer$ spectrometer. The crystal structure of prepared sample was determined to be rhombohedral with space group R-3m. From the temperature dependence of the magnetization curves under 100 Oe between 4.2 and 740 K, two temperature-dependent magnetic transitions occurred in the $Ba_2Co_{1.5}Mg_{0.5}Fe_{11.88}Ga_{0.12}O_{22}$ sample. $M{\ddot{o}}ssbauer$ spectra of the sample were analyzed at various temperatures ranging from 4.2 to 620 K, and the $Ba_2Co_{1.5}Mg_{0.5}Fe_{11.88}Ga_{0.12}O_{22}$ sample showed abrupt changes in $H_{hf}$ and $E_Q$ at 200 K, indicating the spin transition effect. We have also determined the magnetic transition temperature $T_C$, in addition to the temperature dependent magnetization and ZVC measurements.

  • https://doi.org/10.3938/jkps.73.1708 인용 KSCI

자유 단조의 소성불안정 유동에 관한 연구 (A Study on the Pladstic Instable Flow in Free Forging)

  • 이용성
    • 한국소성가공학회:학술대회논문집
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    • 한국소성가공학회 2000년도 춘계학술대회논문집
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    • pp.96-100
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    • 2000

  • It is difficult to predict material behavior of forming process because the plastic instable flow phenomenon happens in practical forming process I. e. upsetting backward extrusion piercing indentation. In view of the direct relationship between instable material flow and quality defects of the products we should find out their phenomena, In this study we introduced the plastic spin and the kinematic hardening considering the kinematic hardening constitutive equation for rate-dependent material. Also analysis of upset forging is carried out using the rigid plastic FEM with Al7075

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EFFECTS OF Co-DOPING LEVEL ON THE MICROSTRUCTURAL AND FERROMAGNETIC PROPERTIES OF LIQUID-DELIVERY METALORGANIC-CHEMICAL-VAPOR-DEPOSITED $Ti_{1-x}Co_xO_2$ THIN FILMS

  • Seong, N.J.;Seong, S.G.
    • 한국자기학회:학술대회 개요집
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    • 한국자기학회 2002년도 동계연구발표회 논문개요집
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    • pp.42-43
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    • 2002

  • Spintronics is a rapidly expanding research area because of recent developments in the physics of spin-dependent phenomena. For use as spintronic materials, dilute magnetic semiconductors (DMS) are of considerable interest as spin injectors for spintronic devices.$^{[1]}$ Many researchers have studied DMS, in which transition metal atoms are introduced into the lattice, thus inserting local magnetic moments into the lattice. (omitted)

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