• 제목/요약/키워드: electronic and magnetic structure

검색결과 368건 처리시간 0.024초

B20 결정구조와 MnGe와 MnSi의 전자구조 및 자기적 특성 (B20 Crystal Structure and Electromagnetic Property of MnGe and MnSi)

  • 정태성
    • 한국재료학회지
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    • 제29권8호
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    • pp.477-482
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    • 2019
  • The magnetic properties and electronic structures of the B20 crystal structure MnGe and MnSi were investigated using the density functional theory with local density approximation. The low symmetry of the B20 crystal structure plays a very important role to make electromagnetic characteristics of these materials. The important result of the calculations is that it can be observed the appearance of a pair of gaps in the density of states near the Fermi level in both compounds. These features are results from d-band splitting by the low symmetry of the crystal field from B20 crystal structure. It can be seen that there is half-metallic characteristics from the density of states in both compounds. The calculation shows that the value of magnetic moment of MnGe is 5 times bigger than that of MnSi even though they have same crystal structure. The electronic structures of paramagnetic case have a very narrow indirect gap just above the Fermi level in both compounds. These gaps acquire some significance in establishing the stability of the ferromagnetic states within the local density approximation. Calculation shows that the Mn 3d character dominates the density of states near the Fermi level in both materials.

Characteristics of a Tunable Microstrip Bandpass Filter Under the Influence of Magnetic Field

  • Chow, Hwang-Cherng;Chatterjee, P.;Lin, Kuei-Hung;Feng, Wu-Shiung
    • Journal of Magnetics
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    • 제22권2호
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    • pp.275-280
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    • 2017
  • A magnetic-field tunable 2.4 GHz microwave bandpass filter having insertion loss < -5dB on an FR4 substrate with the flaky magnetic material was designed and characterized. The tunability in the designed bandpass filter was achieved by adhering soft magnetic materials on top of the device. This soft magnetic material can be composed of ferromagnetic substance or ferrimagnetic substance. The performance of the designed bandpass filter under its influence is investigated. The frequency offset ratio changes over 30 %. There is over 20 % change in the center frequency towards the lower frequency region due to this application. These magnetic material layers achieved the center frequency shift and bandwidth extension without actually changing the original structure of the device.

Cubane 구조를 가진 Co4 분자자성체의 전자구조 및 자기구조계산 (Electronic and Magnetic Structure Calculations of Cubane-type Co4 Magnetic Molecule)

  • 박기택
    • 한국자기학회지
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    • 제27권4호
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    • pp.140-144
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    • 2017
  • Co 원자 4개를 포함한 cubane 구조의 분자자성체의 전자구조 및 자기적 성질을 제1원리의 범밀도함수법을 이용하여 계산하였다. 계산된 결과, Co 원자는 +2가를 가지며, 강한 내부 원자의 교환상호작용으로 high-spin 상태를 보여주었다. 스핀배열에 따른 총 에너지 계산에서 수직을 이루는 Co 원자 사이는 강자성, 더 큰 각도를 이루는 Co 원자 사이는 반강자성 교환상호작용이 일어남을 보여주었다. 이러한 원인은 $Co^{+2}(3d^7)$ 원자 사이의 초교환상호작용으로 설명할 수 있었었고, Co 분자자성체는 AFM1 = [${\uparrow}{\uparrow}{\downarrow}{\downarrow}$] 스핀구조를 가지고 있었다.

A New Type of CPPM Machine with Stator Axial Magnetic Ring

  • Xie, Kun;Li, Xinhua;Ma, Jimin;Wu, Xiaojiang;Yi, Hong;Hu, Gangyi
    • Journal of Electrical Engineering and Technology
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    • 제13권3호
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    • pp.1285-1293
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    • 2018
  • This paper proposes a new type of consequent-pole permanent-magnet (CPPM) machine with stator axial magnetic ring that increases torque capability over a wide speed range and enhances efficiency for the built-in rare-earth permanent magnet synchronous machine used in new energy vehicles. The excitation winding of the CPPM hybrid excitation synchronous machine in the stator is replaced by ferrite magnetic ring to simplify the structure and manufacturing process of the machine. The basic structure and magnetic regulation principle of the proposed machine are introduced and compared with the traditional interior rare-earth permanent magnet synchronous machine and CPPM hybrid excitation synchronous machine. Finally, experimental results of a new type of CPPM synchronous motor prototype with axial magnetic ring are introduced in the paper.

Ferromagnetic Properties in Diluted Magnetic Semiconductors (Al,Mn)N grown by PEMBE

  • Ham, Moon-Ho;Myoung, Jae-Min
    • Transactions on Electrical and Electronic Materials
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    • 제7권1호
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    • pp.12-15
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    • 2006
  • We present the structural, magnetic, and electrical properties in the (Al,Mn)N films with various Mn concentrations grown by plasma-enhanced molecular beam epitaxy. X-ray diffraction analyses reveal that the (Al,Mn)N films have the wurtzite structure without secondary phases. All (Al,Mn)N films showed the ferromagnetic ordering. Particularly, ($Al_{1-x}Mn_{x}$)N film with x = 0.028 exhibited the highest magnetic moment per Mn atom at room temperature. Since all the films exhibit the insulating characteristics, the origin of ferromagnetism in (Al,Mn)N might be attributed to either indirect exchange interaction caused by virtual electron excitations from Mn acceptor level to the valence band within the samples or a percolation of bound magnetic polarons arisen from exchange interaction of localized carriers with magnetic impurities in a low carrier density regime.

FePd 인공격자박막의 나노구조 및 자기적 특성 (Nano-structure and Magnetic Properties of FePd Superlattice Thin Film)

  • 강준구;정인식;구정우;고중혁;구상모;남송민;하재근
    • 한국자기학회지
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    • 제18권5호
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    • pp.190-194
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    • 2008
  • FePd 합금박막을 스퍼터링법으로 초격자 박막의 형태로 제작하고 기판온도, 조성변화에 따른 미세구조 및 자기적 특성을 분석하였다. FePd 합금박막의 규칙화를 위한 열처리 온도를 FePt의 열처리 온도에 비해 $150^{\circ}C$ 낮추는데 성공하였다. 또한 FePd 규칙화 합금 박막은 화학양론적 조성일 때 장범위 규칙도는 가장 높은 값을 가졌으며(Fe조성 50 at.%, S = 0.79), 자기이방성 에너지는 Fe 조성이 약간 낮은 조성에서(Fe조성 48 at.%, $K_U=1.6{\times}10^7\;erg/cm^3$) 가장 높은 값을 나타내었다. 이것은 FePd 합금박막의 조성이 장범위 규칙도와 수직자기이방성에 직접적으로 영향을 미친다는 것을 나타낸다.

질화탄소 박막 증기 증착 시 자장이 결정 구조 성장에 미치는 영향 (The influence of a magnetic field on a crystalline structure of carbon nitride deposition)

  • 김종일;배선기;박희석
    • 한국전기전자재료학회:학술대회논문집
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    • 한국전기전자재료학회 2001년도 하계학술대회 논문집
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    • pp.165-169
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    • 2001
  • Carbon nitride films were grown on Si (100) substrate by a laser-electric discharge method with and without a magnetic field assistance. The magnetic field leads to vapor plume plasma expending upon the ambient arc discharge plasma area. Influence of the magnetic field has resulted in increase of a crystallite size in the films due to bombardment (heating) of Si substrates by energetic carbon and nitrogen species generated during cyclotron motion of electrons in the discharge zone. Many crystalline grains were observed in the morphology of the deposited films by scanning electron microscopy. In order to determine the structural crystalline parameters, X-ray diffraction (XRD) was used to analysis the grown films.

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Structural, Magnetic, and Electronic Properties of Fe: A Screened Hybrid Functional Study

  • Jang, Young-Rok;Yu, Byung-Deok
    • Journal of Magnetics
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    • 제16권3호
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    • pp.201-205
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    • 2011
  • We performed total energy and electronic structure calculations for the basic ground state properties of Fe using the conventional generalized gradient approximation (GGA) and screened hybrid functionals as the form of the exchange-correlation functional. To that end, we calculated structural (equilibrium lattice constants, bulk moduli, and cohesive energies) and electronic (magnetic moments and densities of states) properties. Both functional calculations gave the correct ground state, the ferromagnetic bcc phase, in which the structural parameters agreed well with experimental results. However, the description of the cohesive energies and magnetic moments at the ground state exhibited different behavior from each other: the unusually small cohesive energy and large magnetic moment were observed in the screened hybrid functional calculations compared to the GGA calculations. The reason for the difference was examined by analyzing the calculated electronic structures.

Liquid Chromatography-Solid Phase Extraction-NMR (LC-SPE-NMR) Analysis of Liquid Crystalline Mixtures

  • Park, Gregory Hyung-Jin;Park, Ae-Na;Rho, Kyung-Rae;Shin, Jong-Ho;Kim, Yeong-Jeon;Jo, Sung-Chan;Oh, Weon-Sik
    • 한국자기공명학회논문지
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    • 제15권1호
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    • pp.14-24
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    • 2011
  • We have performed Liquid Chromatography-Solid Phase Extraction-NMR (LC-SPE-NMR) analysis for liquid crystalline mixture and elucidated the structures of selected components by NMR spectra. Combining the results of one-dimensional 1H experiments as well as homonuclear and heteronuclear two-dimensional experiments, we could analyze the molecular structure of the liquid crystal singles whose structure had not been interpretable by mass spectrometry alone.

Possibility of Magnetocapacitor for Multilayered Thin Films

  • Hong, Jong-Soo;Yoon, Sung-Wook;Kim, Chul-Sung;Shim, In-Bo
    • Journal of Magnetics
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    • 제17권2호
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    • pp.78-82
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    • 2012
  • CoNiFe(CNF)/$BaTiO_3(BTO)$/CoNiFe(CNF) multilayered thin films were deposited on Pt/Ti/$SiO_2$/Si substrates by using pulsed laser deposition (PLD) system. We fabricated three different thin films of BTO, BTO/CNF and CNF/BTO/CNF for magneto-capacitor and studied their crystalline structure, surface and interface morphology, and magnetic and electrical properties. When three different structures of multilayered thin film were compared, magnetization of CNF/BTO/CNF thin films was decreased by magnetic and dielectric interaction. Also we confirmed that capacitance of CNF/BTO/CNF multilayered thin film was enhanced as being near tetragonal structure with increasing of c/a ratio because of atomic bonding at interface between BTO dielectric and CNF magnetic materials. Finally, we studied the change of the capacitance of CNF/BTO/CNF multilayered thin film with magnetic field for emergence of magnetocapacitance and suggested a possibility of enhanced capacitance.