• Journal of the Korean Magnetics Society
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• v.24 no.4
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• pp.97-100
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• 2014

We have studied electronic and magnetic structure of Mn-dimer molecule using OpenMX method based on density functional method. The calculated density of states shows that the four O atoms split $e_g$ and $t_{2g}$ energy levels. The energy splitting by the crystal field is smaller than bulk MnO with cubic structure, because of small coordination number of atoms. Total energy with antiferromagnetic spin configuration is lower than that of ferromagnetic configurations. Calculated exchange interaction J between Mn atoms is one order larger than that of the other Mn-O magnetic molecules. That comes from the direct exchange interaction between Mn 3d orbitals and the super-exchange interactions caused by strong ${\sigma}$-bonding of Mn-O orbitals.

• Journal of the Korean Magnetics Society
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• v.27 no.4
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• pp.140-144
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• 2017

We have studied electronic and magnetic structure of cubane-type Co magnetic molecule using density functional method. The calculated density of states show $Co^{+2}$ ionic state and high-spin state because of large exchange interaction between inside Co 3d electrons. The exchange interaction J between Co atoms depends Co-O-Co angle. The calculated J is ferromagnetic with right angles. On the other hand J is antiferromagnetic with large angles since super-exchange interactions between $Co^{+2}$ atoms. It induces that Co cubane has a antiferromagnetic spin structure of AFM1 = [${\uparrow}{\uparrow}{\downarrow}{\downarrow}$]

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.27 no.5
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• pp.249-255
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• 2017

Using a magnetic separation process, pond ash generated in thermoelectric power plants was separated into magnetic materials and nonmagnetic materials in order to make it into a raw material of geopolymers and unburned carbon; screening characteristics according to the particle sizes and magnet strength levels of the pond ash were observed. Based on the results of magnetic separation into fine particle (0.15~0.84 mm) and rough particle (0.84~2.4 mm) pond ash using 3000 G magnets, the weight fraction and ignition loss of nonmagnetic materials were found to be higher than those of magnetic materials, regardless of the particle size. In the case of fine particle pond ash, when the magnet strength was increased from 3000 G to 10000 G, even those materials that were weakly magnetic were separated into magnetic materials, leading to drastic increases in the weight fraction of magnetic materials, such that the ignition loss accounted for 66.9 % (22.8 wt%) of the entire ignition loss of 32.6 wt%, despite of the low ignition loss. Based on the results of measurement of the compressive strength levels of geopolymers made of magnetic-separated rough particle pond ash, the compressive strength of geopolymers made of magnetic materials containing small amounts of unburned carbon was found to be 20 MPa.

• Electronics and Telecommunications Trends
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• v.10 no.3 s.37
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• pp.151-163
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• 1995

최근 이동통신, 위성통신 등 통신시스템의 급속한 발달과 더불어 마이크로파대에서 이용될 수 있는 통신기기의 개발이 시급히 요구되고 있다. 더우기 주파수자원의 활용범위가 고주파 광대역화되어 감에 따라 새로운 부품의 개발이 대두되고 있다. 그중 페라이트 자성체를 이용한 마이크로파 부품은 가용주파수 대역을 고주파화 및 광대역화할 수 있으므로 이동통신, 위성통신 시스템 등에 활용가능성이 새로이 제안되고 있다. 본 고는 자성체를 이용한 마이크로파 부품들인 칩인덕터, 박막인덕터, 정자파소자, 위상변위기 등의 개발현황에 대해 조사분석한 것이다.

• Proceedings of the KIPE Conference
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• 2013.11a
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• pp.224-226
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• 2013

본 논문은 유도가열 시스템의 자성체 판별 알고리즘을 제안한다. 코일의 형상 및 구성에 따른 임피던스를 수학적으로 분석하여 자성체와 비자성체 동시 가열을 위한 유도 코일을 능동적으로 설계 한다. 또한 인버터 출력전압과 부하 전류를 센싱하여 계산한 임피던스 값과 수식으로 구한 부하 임피던스를 비교해 가열 용기의 재질을 판별한다. 제안된 알고리즘을 통해 자성체 및 비자성체 유도가열을 하나의 공진형 인버터로 구현할 수 있다. 제안된 판별법은 시뮬레이션을 통해 검증한다.

• Proceedings of the KIEE Conference
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• 2008.04c
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• pp.68-70
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• 2008

본 논문은 전자기원리를 이용하여 배관 내 자성체 이동량을 측정 가능한 자계 인가 시스템을 설계하고자 한다. Single 코일 타입, Helm-Holtz 코일타입, 수직자계, 반도체 소자 이용한 타입의 4가지 형태에 대해 전류 Source, 주파수, 배관 재질을 달리하여 설계 및 해석하였다. 전원이 AC일 경우 주파수가 높을수록, 배관의 도전율이 높을수록 자성체의 측정 정밀도를 감소시키며 DC 전원일 때 수직자계에서 반도체 소자를 이용하여 측정 정밀도를 높인다.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.10 no.1
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• pp.135-139
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• 2009

Developer roller of laser printer cartridge made with magnetic substance and density of magnetic flux was decreased with the elapse of a year. Owing to this reason, quality of printing was decreased with decreasing of magnetic flux. This study investigated about the elapse of a year of magnetic substance and possible about usage of recycling production.

• Proceedings of the Korean Magnestics Society Conference
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• 2002.12a
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• pp.230-231
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• 2002

고주파전류가 통전되고 있는 연자성체에 외부자계가 인가되면 자성체의 표피효과(Skin effect)에 의해서 임피던스가 변화하게 된다. 따라서 고주파의 정전류를 통전시키면 자성체의 양단에서 전압의 크기는 외부에서 인가되는 자계에 따라 변화하게 되는데, 이 때의 전압을 자계로 환산함으로써 자계의 검출이 가능하다. 이러한 현상을 이용하여 자계를 검출하는 소자를 자기임피던스 센서(Magneto-Impedance sensor)라고 한다$^{1.2}$ . 자기임피던스 센서는 주로 연자성이 우수한 아몰퍼스 자성체를 이용하여 구성되고, 구조가 간단하며, 극히 우수한 자계 검출능력을 나타내므로, 차세대의 고감도 자계센서로서 주목을 받고 있다. (중략)

• Journal of the Korea Organic Resources Recycling Association
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• v.19 no.4
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• pp.90-96
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• 2011

In order to remediate contaminated soils with heavy metals, many techniques have been developed and proposed. However, weakness for the various techniques has been making application for actual process difficult. They have been led to the necessity for novel techniques. Therefore, in this study, novel techniques which are developing and commercializing recently in domestic/foreign country will be introduced, especially it will be focused on remediation technique for contaminated soil with heavy metals using magnetic material.

• Journal of the Korean Magnetics Society
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• v.14 no.2
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• pp.83-88
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• 2004

Magnetism of molecular nanomagnet, which attracted a lot of academic attention after the discovery of the macroscopic quantum tunneling of magnetism, is reviewed. Molecular nanomagnet is metal-organic material in which magnetic ions are regularly located in the organic skeleton. Also, the interaction between the molecules is very small and those molecules form macroscopic molecular crystal in which molecules are residing at the element points in the crystal. Molecular nanomagnets show a lot of interesting features, especially, equivalence of macroscopic magnetic properties and molecular magnetic properties. In this paper, research results on molecular nanomagnet with microscopic tool like NMR are reviewed mainly. The new method to observe the quantum tunneling of magnetization discovered in Mnl2-ac with NMR is shown and the research results on the microscopic aspects of the macroscopic quantum tunneling of magnetization using the new method are shown. Also, the physical aspect of the level crossing effect which has been reported originally with NMR in molecular nanomagnet is reviewed with experiment results. The research results on the molecular nanomagnets will reveal the important information about the limit of the miniaturization of magnetic memory units and give us the basic scientific knowledge which is needed for the application for the quantum computation. Moreover, academically, many quantum mechanical theories which have not been checked the validity can be checked with experiments.