Choong-Jin Yang

Seoul National University of Science and Technology

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Caiyin You

Xi'an University of Technology

Xia Sun

University of British Columbia

Jong-Soo Han

Research Institute of Industrial Science and Technology

Wooyoung Lee

Yonsei University

Zhidong Zhang

University of Science and Technology of China

JongSoo Han

Research Institute of Industrial Science and Technology

Seung-Duck Choi

Research Institute of Industrial Science and Technology

Z. D. Zhang

Shenyang Institute of Automation

Sang-Moo Han

Sogang University

Cai-Yin You

Cooperative Institutions

Chinese Academy of Sciences

Research Institute of Industrial Science and Technology

International Centre for Materials Physics

Korea Advanced Institute of Science and Technology

Pohang University of Science and Technology

Soongsil University

Kyungpook National University

Yonsei University

Hanyang University

Electronics and Telecommunications Research Institute

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Nanoparticle Phosphors Synthesized by Inductively Controlled Plasma Process for Plasma Based Display

Journal of the Korean Ceramic Society (2008)

Choong-Jin Yang Jong‐Il Park Seung-Dueg Choi Eon-Byeong Park Young Ju Lee

Plasma display

10.4191/kcers.2008.45.7.380

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Magnetic Properties and Magnetization Reversal of Sm–Co(3 x nm)/Co( x nm) Multilayered Films

Journal of materials research/Pratt's guide to venture capital sources (2004)

Caiyin You Choong-Jin Yang Zhidong Zhang JongSoo Han X. K. Sun

Single domain

10.1557/jmr.2004.0102

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Magnetic Properties and Magnetization Reversal of Sm–Co(3x nm)/Co(x nm) Multilayered Films

Journal of materials research/Pratt's guide to venture capital sources (2004)

Caiyin You Choong-Jin Yang Zhidong Zhang JongSoo Han Xia Sun

Single domain

10.1557/jmr.2004.19.3.786

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Rapidly Solidified Fe - 6.5wt% Si Alloy Powders for High Frequency Use

Journal of Magnetics (1997)

SeungDueg Choi Choong-Jin Yang

Fe-(3~6.5wt%) Si alloy powders having a high magnetic induction(Bs) and a low core loss value for high frequency use were obtained by an extractive melt spinning as well as a centrifugal atomization technique. Sintered core rings made by the rapidly solidified Fe-6.5wt% Si powders exhibited the high frequency magnetic properties : magnetic induction(B8) of 1.23 T, coercivity(Hc) of 0.12 Oe, relative permeability(μ₃) of 6321, and core loss(W10/50) of 1.27 W/㎏ from the rings of 1.1 ㎜ thick. The magnetic induction values were found to be almost identical to those of non-oriented Fe-3wt% Si steel sheet and double the value of 6.5wt% Si sheet prepared by the CVD technique. The high frequency core losses(W) up to 10 ㎑(W10/10k) were measured to be competitive to those of grain-oriented Fe-3wt% Si steel sheet.

Relative permeability

Melt spinning

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The Presence and Role of Intergranular Phase in Nd₈Fe_86-xNb_xB₆(x = 0, 1, 2, 3) Nanocomposite Magnet Characterized by Mossbauer Spectroscopy

Journal of Magnetics (2005)

Jong-Soo Han Choong-Jin Yang Eon-Byeung Park Eng-Chan Kim

Precisely refined Mossbauer study and nano structure observation revealed that intergranular phase formed between a-Fe and Nd₂Fe₁₄B phase in NdFeNbB alloys plays a significant role on the magnetic properties. The intergranular interaction was characterized in term of Henkel Plot (δM plot), and hyperfine field, quardrupole splitting and isomer shift were refined to predict the presence and role of the intergranular phase. By the addition of Nb into Nd₈Fe₈₆B₆ composition, coercivity was found to increase by 25% due to the refinement of average grain size of both the soft and hard magnetic phases which was decreased from 50 nm of virgin Nd/sub 8/Fe/sub 86/B/sub 6/ to 25 nm in Nd₈Fe₈₅Nb₁B₆ alloys. The role of Nb addition was confirmed to stabilize the Nd₂Fe₁₄B lattice preventing from thermal vibration of the corresponding sites substituted Fe by Nb atoms in all sites in the Nd₂Fe₁₄B lattice. The enhanced coercivity was originated from the exchange hardening of soft and amorphous phases surrounding the hard magnetic Nd₂Fe₁₄B crystal.

10.4283/jmag.2005.10.1.014

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Broad dual-band PIFA using self-complementary structure for DVB-H applications

Electronics Letters (2010)

Choong-Jin Yang Chang Won Jung

A dual-band (UHF: 470–862 MHz, L: 1452–1492 MHz) digital video broadcasting-handheld (DVB-H) antenna is presented. The proposed antenna is composed of a planar inverted F-shape antenna (PIFA) with a self-complementary structure for the broadband performance. The measured operation bandwidth of the antenna (VSWR<4) is 500 MHz (370–870 MHz) at UHF band and 220 MHz (1300–1520 MHz) at L-band. The proposed antenna has an approximately omnidirectional radiation pattern and sufficient gain (average peak gain; −1.74 dBi over 470–862 MHz) for DVB-H applications.

Multi-band device

Digital Video Broadcasting

10.1049/el.2010.0512

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A Study of Magnetic Field Annealing on Microstructures and Magnetic Properties of Nanocomposite Sm-Co/Co Films

Journal of Magnetics (2002)

Choong-Jin Yang Cai-Yin You Z. D. Zhang Kyung-Soo Kim Jong-Soo Han

A magnetic field annealing is firstly used for nanostructured Sm-Co/Co films, prepared by magnetron sputtering method. The effects of magnetic field annealing on single-layered Sm-Co films are different from those on multi-layered Sm-Co/Co films. A detailed analysis of microstructures and magnetic properties is made by means of HRTEM, Auger electron spectroscopy, XRD and Physical Property Measurement System (PPMS). From magnetic properties and microstructure analysis, it was confirmed that these differences originate from the effects of magnetic field annealing on crystallization behavior of the films. The relationship between magnetic properties and microstructures explains a different demagnetization process of single-layered and multilayered films. For the single-layered Sm-Co films, magnetic-field-annealing makes the main phases change from $CaCu_5/ to Zn_2Th_{17}$ structure, resulting in a decrease of coercivity. The results show that the magnetic-field-annealing is useful to improve the properties of nanostructured Sm-Co(30 nm)/Co(10 nm) films, which ascribe to improving the pinning effectiveness in coercivity mechanism and decreasing the magnetostatic interaction of films. A very high coercivity about 0.7 T was obtained from nanoscaled multi-layered Sm-Co(30 nm)-/Co(10 nm) films.

10.4283/jmag.2002.7.2.045

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Sr-Ferrite Magnetic Powders with High Characteristics by the New Process of Co-spray Roasting

한국자기학회 학술연구발표회 논문개요집 (2010)

Hyo-Jun Kim Choong-Jin Yang Tae-Sik Cho

Roasting

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X-ray refinement and magnetic properties of nitrogenated melt-spun Sm2Fe17 compound

Journal of Applied Physics (1993)

Choong-Jin Yang Wooyoung Lee Hyung-Sup Shin

Sm2Fe17N2.9 compound powders were prepared from parent alloys of Sm2Fe17 which were made by both the arc-melting and rapid solidification processes. The cast Sm2Fe17 contained mixed phases of SmFe3 and α-Fe, and correspondingly formed less Sm2Fe17Nx with a rather large amount of residual α-Fe after nitrogenation. The melt-spun Sm2Fe17 compound, however, was single phase and exhibited a negligible amount of residual α-Fe after nitrogenation. The residual amount of free iron was found to increase as a function of milling time and impede the development of promising permanent magnetic properties. The melt-spun Sm2Fe17Nx compound powders exhibited a coercivity value iHc of 5 kOe, which is double that of the as-cast Sm2Fe17Nx powders and a high remanence, Br=60 emu/g. The average magnetic moment of Fe atoms in the crystal is estimated to be 2.29 μB and the Fe atom in the 6c site shows the highest magnetic moment of 2.65 μB. The expansion in the c-axial direction of the nitrogenated crystal was found to be mainly due to extension of Sm(6c)-Fe(6c) and Fe(18f)-Fe(18f) distances.

Melt spinning

10.1063/1.355082

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THE EFFECT OF HfB₂ ON MAGNETIC PROPERTIES OF NANOCOMPOSITE Fe₂Nd₁₄B / Fe₃B MAGNET

한국자기학회지 (1995)

Choong-Jin Yang ChanWook Kim EyunByung Park

By adding lwt.% HfB₂ into Nd_(3-4)Fe_(77-78.5)B_(18.5) alloys, the grain growth of Fe₃B/Nd₂Fe₁₄B composite phases during annealing was found to be hindered by 40~50%. It is proposed that the addition of HfB₂ leads to the formation of fine dispersoids of HfB₂ in the Fe₃B/Nd₂Fe₁₄B composite magnet. The maximum energy product((B.H)max) as well as intrinsic coercivity(iHc) for the Nd₃Fe_(78.5)B_(18.5)+lwt.% HfB₂ alloy were enhanced by more than 25% (B.H)max=10 MGOe, iHc=2.5 kOe) due to the addition of HfB₂ while remanent magntization(Br) was reduced slightly. It is deduced that the formation of fine dispersoids will also play a role of magnetic domain pinning.

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