1. CrPt3(001) 박막의 자성: 제일원리계산

    Tae Sung Jeong , Soyoung Jekal , S. H. Rhim and S. C. Hong

    Journal of the Korean Magneitcs Society, 30 Apr 2017, Vol.27 , No.2, pp.41-48

    Number of citation : 0

    CrPt3(001) 박막의 자성: 제일원리계산

    Recent study shows that ordered alloy of L12 XPt3 (M= V, Cr, Mn, Co, and Fe) exhibits various magnetic phases such as ferromagnetic-to-antiferromagnetic transition at the MnPt3 surface. Moreover, it has been argued that CrPt3, in particular, possess large magnetocrystalline anisotropy and Kerr rotation with possible violation of Hund’s rule. As such, we extend our work to thickness dependence of the magnetic structure of CrPt3 thin film using density functional theory. Magnetic ground state of the bulk CrPt3 turns out to be ferromagnetic (FM), where other magnetic phases such as A-type (A-AF), C-type (C-AF), and G-type antiferromagnetic (G-AF) state have higher total energies than FM by 0.517, 0.591, and 0.183 eV, respectively, and magnetic moments of Cr in bulk are respectively 2.807 (FM), 2.805 (A-AF), 2.794 (C-AF) and 2.869 μB (G-AF). We extend our study to CrPt3(001) thin films with CrPt- and Pt-termination. The thickness and surface-termination dependences of magnetism are investigated for 3-9 monolayers (ML), where different magnetic phases from bulk emerge: C-AF for CrPt-terminated 3ML and G-AF for Pt-terminated 5ML have energy difference relative to FM by 8 and 54 meV, respectively. Furthermore, thickness- and surface-termination-dependent magnetocrystalline anisotropies of the CrPt3(001) films are discussed.

  2. THz 대역에서 Cut Wire로 구성된 메타소재의 자기공진 및 전파흡수특성

    Yo-Han Ryu and Sung-Soo Kim

    Journal of the Korean Magneitcs Society, 30 Apr 2017, Vol.27 , No.2, pp.49-53

    Number of citation : 0

    THz 대역에서 Cut Wire로 구성된 메타소재의 자기공진 및 전파흡수특성

    Metamaterials composed of split cut wire (SCW) on grounded polyimide film substrate have been investigated for the aim of electromagnetic wave absorbers operated in THz frequency band. Reflection loss and current density distributions are numerically simulated with variations of the SCW geometries using the commercial software. The minimum reflection loss lower than −20 dB has been identified at 5.5~6.5 THz. The simulated resonance frequency and reflection loss can be explained on the basis of the circuit theory of an inductance-capacitance (L-C) resonator. Dual-band absorption can be obtained by arrangement of two SCWs of different length on the top layer of the grounded substrate, which is due to multiple magnetic resonances by scaling of SCWs. With increasing the side spacing between SCWs, a more enhanced absorption peak is observed at the first resonance frequency that is shifted to a lower frequency.

  3. d-q축 등가회로 해석기법을 이용한 180 W급 IPMSM 설계에 관한 연구

    Young-Kyoun Kim

    Journal of the Korean Magneitcs Society, 30 Apr 2017, Vol.27 , No.2, pp.54-62

    Number of citation : 1

    d-q축 등가회로 해석기법을 이용한 180 W급 IPMSM 설계에 관한 연구

    This paper presents a design of the Interior Permanent Magnet Synchronous Motor (IPMSM). an initial design process is accomplished by using the parametric design. In the design process, motor characteristics of parameters is computed by the d-q axis equivalent circuit model. Then, an optimal design process is accomplished by combination the experimental design and the response surface method. Finally, the design and analysis results are verified with experimental results.

  4. 축소 모델 함정을 이용한 소자 최적화 기법의 해석적 검증

    Dong-Jin Cho

    Journal of the Korean Magneitcs Society, 30 Apr 2017, Vol.27 , No.2, pp.63-69

    Number of citation : 0

    축소 모델 함정을 이용한 소자 최적화 기법의 해석적 검증

    Naval ships are particularly required to maintain acoustic and magnetic silence due to their operational characteristics. Among them, underwater magnetic field signals derived by ships are likely to be detected by threats such as surveillance systems and mine systems at close distance. In order to increase the survivability of the vessels, various techniques for reducing the magnetic field signal are being studied and it is necessary to consider not only the magnitude of the magnetic field signal but also the gradient of it. In this paper, we use the commercial electromagnetic finite element analysis tool to predict the induced magnetic field signal of ship’s scaled model, and arrange the degaussing coil. And the optimum degaussing current of the coil was derived by applying the particle swarm optimization algorithm considering the gradient constraint. The validity of the optimal degaussing technique is verified analytically by comparing the magnetic field signals after the degaussing with or without gradient constraint.

  5. 자기 포화 영역을 갖는 단상 6/6 SRM의 자기 구조 해석 및 개선

    Seok-Gyu Oh

    Journal of the Korean Magneitcs Society, 30 Apr 2017, Vol.27 , No.2, pp.70-75

    Number of citation : 0

    자기 포화 영역을 갖는 단상 6/6 SRM의 자기 구조 해석 및 개선

    Single-phase SRM is cost competitive because it can reduce the number of switches for small, low-cost applications. However, since the single-phase SRM is difficult to start itself, methods for realizing self-starting by using auxiliary magnet or auxiliary pole have been studied. Recently, a method of self-starting by changing the shape of the rotor with a saturable area has been proposed. The purpose of this paper is to analyze the magnetic structure of single phase 6/6 SRM with a saturable rotor and to improve the magnetic structure of rotor with a saturable area. For this magnetic analysis, FLUX2D, a finite element method analysis program, was used.