• Journal of Magnetics
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• 제17권2호
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• pp.100-108
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• 2012

Flux concentrated permanent magnet transverse flux machines, FCPM-TFMs, with segmented stators require multi-turn concentric saddle coils to replace the ring coils, which are normally utilized in conventional layeredphase TFM constructions. In this paper, we investigate the influence of the shape of saddle phase windings and their parameter variations on the output torque productivity. Non-meshed coils evaluated via a finite element method (FEM) to examine the effect of the coil's location within one phase on machine performance. By using meshed coils, the analysis can be extended to inspect the distributions of magnetic field strength as well as current density in the coils. Throughout the study, the influence of design parameters on the output torque for two stator structures, i.e., a laminated and soft magnetic composite (SMC), are evaluated.

• Journal of Magnetics
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• 제19권4호
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• pp.349-352
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• 2014

The system for producing magnetic field constitutes an important component of magnetic refrigerator. Many researchers have directed significant effort to increase the magnetic field intensity, because the magnetocaloric effect at the Curie temperature increases with the power of 2/3 of the magnetic field. In this study, we report the simulation of the magnetic field intensity at polar axis of a Halbach cylinder (HC) by i) changing the length and thickness of the HC, ii) having with or without gap of the HC, and iii) surrounding the HC with a soft magnet shell, acting as a shielding. We simulated the field distribution of a HC with a finite size. Furthermore, the detailed numerical results of the magnetic field distribution and its dependence on shielding are presented in this study.

• 한국자기학회지
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• 제10권2호
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• pp.93-98
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• 2000

자기 광학 공간 광 변조기의 화소의 자화를 반전시키기 위하여 사용하는 드라이브 라인의 형상을 컴퓨터 시뮬레이션을 통하여 설계하고, 연자성막을 도입함으로써 화소 반전에 필요한 최소 전류와 소비 전력을 기존의 드라이브 라인에 비하여 약 3배 감소시킬 수 있었으며, 드라이브 라인을 묻지 않고, 화소를 덮는 반사막(드라이브 라인)의 면적을 크게 하여 광효율을 2.2배 증가시키고, 제조공정을 대폭 단순화시킬 수 있는 드라이브 라인의 형상을 제시했다.

• Journal of Magnetics
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• 제20권3호
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• pp.252-257
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• 2015

This paper investigates the concept and implementation of an energy harvesting device using a ferrofluid sloshing movement to generate an electromotive force (EMF). Ferrofluids are often applied to energy harvesting devices because they have both magnetic properties and fluidity, and they behave similarly to a soft ferromagnetic substance. In addition, a ferrofluid can change its shape freely and generate an EMF from small vibrations. The existing energy harvesting techniques, for example those using piezoelectric and thermoelectric devices, generate minimal electric power, as low as a few micro-watts. Through flow analysis of ferrofluids and examination of the magnetic circuit characteristics of the resultant electromagnetic system, an energy harvester model based on an electromagnetic field generated by a ferrofluid is developed and proposed. The feasibility of the proposed scheme is demonstrated and its EMF characteristics are discussed based on experimental data.

• Journal of Magnetics
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• 제1권1호
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• pp.31-36
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• 1996

An externally applied magnetic field during heat treating the $Nd_2Fe_{14}B/Fe_3B$ based spring magnet was found to enhance the exchange coupling between the hard and soft magnetic grains. More than 30% increase in $M_r/M_s$ values for melt-spun $Nd_2Fe_{73.5}Co_3$$(Hf_{1-x}Ga_x)B_{18.5}$ (x=0, 0.5, 1) alloys was resulted from a uniform distribution of $Fe_3B, \alpha-Fe$ and $Nd_2Fe_{14}B$ phases, and also from a reduced grain size of those phases by 20%. The externally applied magnetic field induced a uniform distribution of fine grains. A study of Mossbauer effect also report that the enhancement of total magnetization of nanocomposite $Nd_2Fe_{14}B/Fe_3B$ alloys is attributed to an increased formation of $Fe_3$B after magnetic annealing.

• 한국자기학회지
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• 제11권1호
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• pp.32-37
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• 2001

건축물내 바닥면에서의 지자기장 분포에 대한 모사실험과 측정을 통하여 철골이 지자기의 분포에 미치는 영향을 연구하였다. 지자기 분포에 대한 모사시험은 유한요소법으로 수행하였으며, 바닥면에서 지자기장의 수직분력(Z)은 플럭스 게이트형 마그네토미터로 측정하였다. 수평으로 배열된 철골은 지자기장의 Z성분 분포에 미치는 영향이 비교적 적으나, 수직으로 배열된 철골은 토의 분포에 강한 영향을 주어 국소 지자기 교란을 일으킨다. 이러한 국소 지자기 교란은 연자성체로 이루어진 바닥이나 우회로 구조를 가지는 연자성체 바닥으로 완화된다.

• 한국자기학회지
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• 제10권6호
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• pp.302-309
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• 2000

박강판의 내부에 존재하는 개재물성 결함을 검사하기 위해 누설자속법을 이용하여 탐상하는 시스템을 개발하였다. 연자성 코어의 보자력을 이용한 차등형 플럭스게이트 자력계를 제작하였다. FEM 소프트웨어를 이용하여 전자석을 설계하였으며, 3축 이동이 가능한 누설자속탐상장치를 제작하여 냉연강판을 검사한 결과 개재물성 결함을 검사학 수 있음을 알았다. 누설자속값을 디지털화하여 2차원 이미지로 처리한 결과 냉연강판에 존재하는 개재물성 결함 이외의 결함을 일부 구분할 수 있음을 알았다.

• 한국자기학회지
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• 제10권6호
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• pp.297-301
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• 2000

보자력은 시편의 자화를 0으로 감소시키기 위해서 필요한 임계 자기장의 세기로 강자성체를 연.경 자성체로 구분하는 기준이 된다. 개방자기회로에서 자성재료의 보자력을 간단히 측정할 수 있는 시스템을 구성하고, 데이터지향언어인 LabVIEW를 사용하여 자기장 제어와 데이터 수집이 가능하도록 하였다. 구성한 보자력 측정 장치의 측정범위는 수십 kA/m에서 수십 kA/m이고, 보자력이 14.63 kA/m일 때 합성표준불확도는 $\pm$0.22 kA/m이다.

• Journal of Magnetics
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• 제4권2호
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• pp.39-45
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• 1999

Sandwich structures of$ Nd_2Fe_{14}B/Fe/Nd_2Fe_{14}B $magnetic films have been grown by a KrF excimer laser (λ=248 nm) ablation technique. Magnetic properties were characterized by varying the thickness of hard ($Nd_2Fe_{14}B$) and soft (Fe) magnetic films and the volume fraction as well. In the (x)nm[NdFeB]/(y)nm[Fe]/(x)nm[NdFeB]/(100) Si structure the thickness (x) was varied from 3.6 to 54 nm, and (y) from 15 to 112 nm. At (y) = 15~20 nm where the volume fraction of Fe corresponded to 61~75%, the sandwich structure exhibited an enhanced Mr/Ms and iHc as well from the result of the exchange coupling between the magnetic layers. Experimentally calculated exchange constant$ (A_s) of A_s = 2.5{\times}10^{-10} J/m$ was estimated using the intrinsic coercivity (iHc) of 1.2 kOe at 5 K for the sandwich magnetic trilayers.

• Journal of Magnetics
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• 제14권3호
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• pp.104-107
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• 2009

The effects of the magnetic property variation on current-induced magnetization switching in magnetic tunnel junction with perpendicular magnetic anistoropy (PMA) and the soft magnetic polarization-enhancement layers (PELs) inserted between the layers with PMA and the MgO layer was studied. A micromatnetic model was used to estimate the switching time of the free layer by different applied current densities, with changing saturation magnetization ($M_s$) of the PELs, interlayer exchange coupling between PMA layers and PELs. The switching time could be significantly reduced at low current densities, by increasing $M_s$ of PELs and decreasing interlayer exchange coupling.