• 제목/요약/키워드: Ferromagnetism

검색결과 152건 처리시간 0.029초

Ab initio Study for Electronic Property and Ferromagnetism of (Cu, N, or F)-codoped ZnO

  • Kang, Byung-Sub;Chae, Kwang-Pyo
    • Journal of Magnetics
    • /
    • 제17권3호
    • /
    • pp.163-167
    • /
    • 2012
  • The effects on the ferromagnetism of the O or Zn defect in Cu-doped ZnO with the concentration of 2.77-8.33% have been investigated by the first-principles calculations. The Cu doping in ZnO was calculated to be a kind of p-type ferromagnetic half-metals. When the Zn vacancy exists in Cu-doped ZnO, the Cu magnetic moment increases, while for the O vacancy it is reduced. It is noticeable that the ferromagnetic state was originated from the hybridized O(2p)-Cu(3d)-O(2p) chain formed through the p-d coupling. The carrier-mediated ferromagnetism by nitrogen or fluorine does not depend on their concentration.

(ZnO/Co) 다층 박막에서 ZnO층의 두께가 상온강자성 특성에 미치는 영향 (The Effects of ZnO Sub-layer Thickness on the Room Temperature Ferromagnetism of (ZnO/Co) Multilayer)

  • 강성근;김성동
    • 마이크로전자및패키징학회지
    • /
    • 제25권4호
    • /
    • pp.137-142
    • /
    • 2018
  • (ZnO/Co) 다층박막 구조를 이용하여 Co 도핑한 ZnO의 상온강자성 특성을 조사하였으며, 특히 ZnO 박막층의 두께가 (ZnO/Co) 다층박막의 상온강자성 특성에 미치는 영향을 조사하였다. ZnO 박막층의 두께가 $20{\AA}$, $40{\AA}$일 때 증착상태에서는 각각 반자성과 강자성 특성을 나타내었으며 진공열처리 후에는 모두 강자성 특성을 나타내었다. 특히 ($ZnO\;40{\AA}/Co\;x{\AA}$)는 열처리 후에 음의 잔류자화 거동을 나타내었다. UV-Vis 분석을 통해서 Co 일부가 Zn와 치환되어 위치하고 있음을 확인할 수 있었으며, 열처리 전후에 대한 XPS 및 HRTEM EDS 분석에서 Co 클러스터의 형성은 관찰되지 않았다.

산소 결핍에 따른 Fe가 도핑된 TiO2-δ의 상온 강자성 현상에 관한 연구 (Room-temperature Ferromagnetism in Fe-doped Reduced TiO2-δ)

  • 이희민;김철성;엄영랑;이창규
    • 한국분말재료학회지
    • /
    • 제13권6호
    • /
    • pp.401-407
    • /
    • 2006
  • Effects of oxygen deficiency on the room temperature ferromagnetism in Fe-doped reduced $TiO_2$ have been investigated by comparing the air-annealed $Ti_{0.97}Fe_{0.03}O_2$ compound with secondly post-annealed one in vacuum ambience. The air-annealed sample showed a paramagnetic behavior at room temperature. However, when the sample was further annealed in vacuum, a strongly enhanced ferromagnetic behavior was observed at same temperature. $M{\"{o}}ssbauer$ spectra of air-annealed sample at 295K showed a single doublet of $Fe^{3+}$, suggesting that the Fe ions are paramagnetic. On the other hand, the absorption spectra after vacuum-annealing exhibited two doublets, in which one is the same component with air-annealed sample and the other is new doublet corresponding to $Fe^{2+}$ state. This result suggests that the occurrence of ferromagnetism in reduced sample may be interpreted as the contribution of unquenched orbital moment of $Fe^{2+}$ ions.

Ferromagnetism and p-type Conductivity in Laser-deposited (Zn,Mn)O Thin Films Codoped by Mg and P

  • Kim, Hyo-Jin;Kim, Hyoun-Soo;Kim, Do-Jin;Ihm, Young-Eon;Choo, Woong-Kil;Hwang, Chan-Yong
    • Journal of Magnetics
    • /
    • 제12권4호
    • /
    • pp.144-148
    • /
    • 2007
  • We report on the observation of p-type conductivity and ferromagnetism in diluted magnetic semiconductor $(Zn_{0.97}Mg_{0.01}Mn_{0.02})O:P$ films grown on $SiO_2/Si$ substrates by pulsed laser deposition. The p-type conduction with hole concentration over $10^{18}cm^{-3}$ is obtained by codoping of Mg and P followed by rapid thermal annealing in an $O_2$ atmosphere. Structural and compositional analyses for the p-type $(Zn_{0.97}Mg_{0.01}Mn_{0.02})O:P$ films annealed at $800^{\circ}C$ indicates that highly c-axis oriented homogeneous films were grown without any detectable formation of secondary phases. The films were found to be transparent in the visible range. The magnetic measurements clearly revealed an enhancement of room temperature ferromagnetism by p-type doping.

Room temperature ferromagnetism in diluted magnetic semiconductor $Zn_{l-x}Cr_xTe$

  • Ando, K.;Saito, H.;Zayets, V.;Yamagata, S.
    • 한국자기학회:학술대회 개요집
    • /
    • 한국자기학회 2003년도 하계학술연구발표회 및 한.일 공동심포지엄
    • /
    • pp.266-267
    • /
    • 2003
  • The most distinguishing character of diluted magnetic semiconductors (DMSs) is a strong interaction between sp-carriers and localized d-spins (sp-d exchange interaction). Recently many "room-temperature (RT) ferromagnetic DMS" have been reported. However, it should be noted that their sp-d exchange interactions have not been confirmed yet. The lack of a clear evidence of the sp-d exchange interaction causes the controversy on the origin of the observed ferromagnetism. For the detection of the sp-d exchange interaction, magneto-optical spectroscopy such as a magnetic circular dichroism (MCD) measurement is the most powerful tool. By using the MCD spectroscopy, we have shown the sp-d exchange interactions in Zn$_{l-x}$Cr$_{x}$Te. Recently, we have obtained the RT ferromagnetism in a Zn$_{l-x}$Cr$_{x}$Te (x = 0.20) film.0) film.

  • PDF

산소 결핍된 TiO2-δ 박막의 상온 강자성 연구 (Room-temperature Ferromagnetism in Oxygen-deficient TiO2-δ Thin Films)

  • 박영란;김광주;양우일;이상영;김철성
    • 한국자기학회지
    • /
    • 제16권4호
    • /
    • pp.206-210
    • /
    • 2006
  • 산소결핍(oxygen vacancy) 들이 존재하는 아나타시(anatase) 및 루타일(rutile) 구조의 $TiO_{2-{\delta}}$ 박막들에서 강자성 현상이 상온에서 관측되었다. 시료들에 대한 XPS 측정 결과 $Ti^{3+}$ 이온의 존재가 관측되었으며 산소결핍에 의한 전하 불균형을 상쇄시키기 위하여 생성되는 것으로 해석된다. $TiO_{2-{\delta}}$ 박막에서 나타나는 상온 강자성은 $Ti^{3+}$ 이온들이 가지는 $d^1$ 스핀들의 정렬에 의한 것으로 해석 되어진다. 이와 같은 강자성 스핀 정렬은 산소결핍 자리에 속박된 전자를 중심으로 형성되는 자기 폴라론(magneticpolaron)에 의하여 나타날 수 있다.

Ferromagnetism and Anomalous Hall Effect in p-Zn0.99Mn0.01O:P

  • Kim, Hyun-Jung;Sim, Jae-Ho;Kim, Hyo-Jin;Hong, Soon-Ku;Kim, Do-Jin;Ihm, Young-Eon;Choo, Woong-Kil
    • Journal of Magnetics
    • /
    • 제10권3호
    • /
    • pp.95-98
    • /
    • 2005
  • We report hole-induced ferromagnetism in diluted magnetic semiconductor $Zn_{0.99}Mn_{0.01}$ films grown on $SiO_2/Si$ substrates by reactive sputtering. The p-type conduction with hole concentration over $10^{18}\;cm^{-3}$ is achieved by P doping followed by rapid thermal annealing at $800^{\circ}C$ in a $N_2$ atmosphere. The p-type $Zn_{0.99}Mn_{0.01}O:P$ is carefully examined by x-ray diffraction and transmission electron microscopy. The magnetic measurements for $p-Zn_{0.99}Mn_{0.01}O:P$ clearly reveal ferromagnetic characteristics with a Curie temperature above room temperature, whereas those for $n-Zn_{0.99}Mn_{0.01}O:P$ show paramagnetic behavior. The anomalous Hall effect at room temperature is observed for the p-type film. This result strongly supports hole-induced room temperature ferromagnetism in $p-Zn_{0.99}Mn_{0.01}O:P$.

Simultaneous regulation of photoabsorption and ferromagnetism of NaTaO3 by Fe doping

  • Yang, Huan;Zhang, Liguo;Yu, Lifang;Wang, Fang;Ma, Zhenzhen;Zhou, Jie;Xu, Xiaohong
    • Current Applied Physics
    • /
    • 제18권11호
    • /
    • pp.1422-1425
    • /
    • 2018
  • $NaTa_{1-x}Fe_xO_3$ ($0{\leq}x{\leq}0.40$) nanocubes were synthesized by a relatively low temperature hydrothermal method, using $Ta_2O_5$, $FeCl_3$ and NaOH as the precursors. The UV-vis diffuse reflectance spectra showed that $NaTa_{1-x}Fe_xO_3$ had significant visible-light-absorbing capability, and the absorption edge of $NaTaO_3$ shifted to longer wavelength with the increase of Fe dopants. Moreover, $NaTa_{1-x}Fe_xO_3$ exhibited room-temperature ferromagnetism when $Fe^{3+}$ occupied $Ta^{5+}$ sites in $NaTaO_3$ crystal lattice. The ferromagnetism is mainly attributed to the superexchange interactions between doped $Fe^{3+}$, rather than the contribution of oxygen vacancies caused by Fe doping. Therefore, Fe doping can simultaneously regulate the optical and magnetic properties of $NaTaO_3$ semiconductor, which will enable its potential applications in multifunctional optical-electronics and opticalspintronics devices.