• Proceedings of the KIEE Conference
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• 2000.07b
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• pp.717-719
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• 2000

In this paper, we discussed an optimal design of BLDC motor using rare earth magnet. In motor design using rare earth magnet, because of the characteristics that rare earth magnets have high remanence, the effect of saturation of steel has to be considered. For this, we used nonlinear finite clement method. For optimal design, a Niching genetic algorithm is used. As a result, we found out a set of BLDC motor shapes increasing motor efficiency, and decreasing cogging torque.

• Journal of Powder Materials
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• v.18 no.1
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• pp.24-28
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• 2011

Effect of Cu content on microstructural and magnetic properties of a $(Nd_{26.06},Dy_{6.51})Fe_{bal.}$ $Cu_xB_{0.97}$(wt.%), (x = 0.2, 0.3, 0.4, 0.5) strip-cast was studied. The average inter-lamellar spacing in the free surface and wheel side of the strip cast increased as the Cu content increases. The grain uniformity, the grain alignment, and (00L) texture of the strip cast increased with Cu contents up to 0.4 wt.%. These microstructural changes were attributed to the decrease of the effective cooling rate of the melted alloy caused by the decrease of the melting temperature of resulting from Cu addition. Coercivity and remanence were increased because of the grain alignment and (00L) texture improvement with Cu contents up to 0.4 wt.%.

• Journal of the Korean institute of surface engineering
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• v.29 no.6
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• pp.839-846
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• 1996

Epitaxial (La, Sr)$CoO_3/Pb(Zr,\;Ti)O_3/(La,\;Sr)CoO_3$by pulsed laser deposition for ferroelectric field effect transistor. Epitaxial $LaCoO_3/Pb(Zr,\;Ti)O_3/(La,\;Sr)CoO_3$ heterostructures exhibited 70$\mu C/cm^2$ and 17 $\mu C/cm^2$at a positively and negatively poled states, respectively. On the other hand, epitaxial (La, Sr)$CoO_3/Pb(Zr,\;Ti)O_3/LaCoO_3$heterostructures show the remnant polarization states opposite to the $LaCoO_3/Pb(Zr,\;Ti)O_3/(La,\;Sr)CoO_3$ heterostructures. This indicates that the interface between (La, Sr)$CoO_3$ (LSCO) and $Pb(Zr, Ti)O_3(PZT)$ layers affects the asymmetric polarization remanence through electrochemical nature. The resistivity of $LaCoO_3$ (LCO) layer was found to be dependent on an ambient oxygen, primarily the ambient oxygen pressure during deposition. The resistivity of the LCO layer varied in the range of 0.1-100 $\Omega$cm. It is suggested that, with an appropriate resistivity of the LCO layer, the LCO/PZT/LSCO heterostructure can be used as the ferroelectric field effect transistor.

• Journal of Magnetics
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• v.9 no.2
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• pp.40-46
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• 2004

The magnetic properties of sputtered ($Ni_{83}Fe_{17}/Au/Co/Au$) multilayers with various thicknesses of Au (0.5 {\leq} t_{Au} {\leq} 3 nm), Ni-Fe ($1{\leq}t_{Ni-Fe}{\leq}4nm$) and Co ($0.2{\leq}t_{co}{\leq}1.5nm$) layers were characterized. An alternating in-plane and out-of-plane anisotropy of the ferromagnetic layers was achieved for the structures ($t_{Au}{\geq}1.5nm$) showing a weak coupling between the Ni-Fe layers with an in-plane anisotropy and the Co layers ($0.3{\leq}t_Co{\leq}1.2nm$) with a perpendicular anisotropy. For such a structure, a detailed discussion on the GMR effect is presented, relating to the magnetization reversal from a mutually perpendicular magnetic configuration at the remanence to a parallel one at the saturation. An influence of the dense labyrinth domain structure on the magnetoresistance effect is also addressed.

• Journal of Magnetics
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• v.16 no.3
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• pp.300-303
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• 2011

The effect of the hot-compaction temperature on the microstructure and magnetic properties of anisotropic nanocrystalline magnets was investigated. The hot-compaction temperature was found to impact both the magnetic properties and the microstructure of die-upset magnets. The remanence of the isotropic precursor increases slightly with the improved hot-compaction temperature, and the grains start to grow on the flake boundary at higher hot-compaction temperatures. After hot deformation, it was found that the change in the magnetic properties was the inverse of that observed with the hot-compaction temperature. Microstructural investigation showed that die-upset magnets inherit the microstructural characteristics of their precursor. For the die-upset magnets, hot pressed at low temperature, scarcely any abnormal grain growth on the flake boundary can be seen. For those hot pressed at higher temperatures, however, layers with large equiaxed grains could be observed, which accounted for the poor alignment during the hot deformation, and thus the poor magnetic properties.

• 한국지구물리탐사학회:학술대회논문집
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• 2010.10a
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• pp.43-45
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• 2010

Acquisition of thermoremanent magnetization follows a Boltzman statistics, as such long reaction time in a slowly cooled environment allows more chance to align individual magnetic particles parallel to the external magnetic field. Hence it has been proposed that the slowly cooled rocks often acquire stronger magnetization than the rapidly cooled ones. Such a proposition has been experimentally validated to be true for the fine-grained magnetite- or titanomagnetite bearing basaltic rocks collected from the mid-ocean ridges. However, the effect of cooling-rate on the remanence intensity appears to be insignificant for nominal grain ranges.

• Journal of the Korean Ceramic Society
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• v.29 no.5
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• pp.383-390
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• 1992

We investigated the effect of substrate on the properties of the Ni-Zn-Cu ferrite thin films deposited on SiO2 (1000∼3000${\AA}$) / Si (100) substrate at various conditions by rf magnetron sputtering. A disktype Ni-Zn-Cu ferrite sintered by conventional ceramic process and argon gas were used as a target and a sputtering gas, repectively. The compositions of the thin films measured by EPMA were similar to target composition (Fe: 65.8 at%, Ni: 12.7 at%, Cu: 6.7 at%, Zn: 14.8 at%) irrespective of substrate temperature. Amorphous thin films were deposited when substrate was not intentionally heated, but the films came to crystallize with increasing substrate temperature, and crystalline thin films were deposited at substrate temperature above 200$^{\circ}C$. Below 250$^{\circ}C$ saturation magnetization (Ms), remanence (Mr) and coercivity (Hc) of the ferrite thin film increased with the substrate temperature due to the increase of grain size and the improvement of crystallinity. And above 250$^{\circ}C$, Ms, Mr increased slightly, but Hc of the amorphous thin films increased due to crystallization, whereas that of the crystalline thin films decreased because of grain growth and stress release.

• Journal of Magnetics
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• v.1 no.2
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• pp.75-81
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• 1996

Study on the HDDr Characteristics of Nd16Fe76-xB8Zrx (x=0-2.0) Alloys and the Magnetic Properties of the HDDR Materials Nd16Fe76-xB8Zrx (where x=0-2.0) have been studied to see the effect of Zr addition on HDDR characteristics. A particular emphasis was place upon the anisotropy of the HDDR material. Anisotropy of the HDDR powder material has been evaluated by comparing the remanence values of the aligned sample measured along the aligning direction and the direction perpendicular to it. The HDDR characteristics of the alloys were investigated by means of DAT and TPA. Magnetic chracterisation of the HDDR processed materials was performed using a VSM and a TMA. The magnetic domain structure of the HDDR materials was examined by means of polarised microscope using a solid HDDR processed material. It has veen found that small addition (0.1 at %) of Zr to Nd-Fe-B-type alloy retards thedisproportionatio kinetics of the hydrogenated material. Desorption characteristic of the disproportionated materials has been found not to be affected significantly by the Zr addition. The Zr addition has been found to facilitate size of the powder. As the particle size decreases, the intrinsic coercivity decreases radically, and this is explained in terms of structural damage and/or oxidation caused during mechanical milling. It has also been found that the degree of alignment representing the anisotropic character of the HDDR powder is enhanced with decreasing particle size. Alloys with compositions based on

• Journal of Powder Materials
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• v.17 no.5
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• pp.359-364
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• 2010

In an attempt to optimize the magnetic properties of (Nd, Dy)-Fe-B sintered magnets, hydrogenation and post-sintering heat treatment processes were investigated at various hydrogenation temperatures and heat treatment temperatures. The coercivity of (Nd, Dy)-Fe-B sintered magnets hydrogenated at $400^{\circ}C$ increased to about 1.2 kOe without any detrimental effect on the remanence. Moreover, the coercivity of the magnets was enhanced further by a consecutive $2^{nd}$ and $3^{rd}$ step heat treatment. These results eventually leaded to the reduction of the Dy content in a high coercive (> 30 kOe) (Nd, Dy)-Fe-B sintered magnets, as much as 10%.

• Journal of the Korean Magnetics Society
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• v.14 no.3
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• pp.105-108
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• 2004

Array of magnetic Ni nanostructures has been fabricated on Si substrate by using nanoporous alumina film as a mask during deposition. The nanostructures are truncated cone-shape and the lateral sizes are comparable to height. While the continuous film shows well-defined in-plane magnetization, the nanostructure shows perpendicular component of magnetization at remanence. The hysterectic behavior of nanostructures is dominated by the demagnetizing field instead of interaction among them.