• The Journal of the Korea institute of electronic communication sciences
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• v.16 no.3
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• pp.471-476
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• 2021

Soft magnetic composite (SMC) materials based on powder metallurgy have a number of advantages over the conventional electrical steel sheets commonly used in electric machines. Thus, technologies related to these materials have shown significant improvement in recent years. In general, SMCs are magnetically isotropic owing to the shape of the powder, which makes them suitable for the construction of electric machines with three-dimensional flux and complex structures. However, the materials with isotropic magnetic properties (such as SMCs) have complex vector hysteresis; thus, it is very difficult to predict accurate loss properties. Therefore, we manufactured ring-type specimens of electrical steel sheets and SMC, which analyzed their magnetic properties according to the specimen size, and performed the electromagnetic field analysis of a high-speed permanent magnet (PM) motor driven at 800 Hz or higher using the measured magnetic information to compare the core loss of the motor. The reliability of this paper has been verified by measuring the efficiency after manufacturing the motor.

• Journal of the Korean Magnetics Society
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• v.16 no.4
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• pp.197-200
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• 2006

Amorphous alloys of Co-rich magnetic amorphous films are well known as thpical soft magnetic alloys. They are used for many kinds of electric and electronic parts such as magnetic recording heads, transformers and inductors. CoFeHfO thin films were prepared by RF magnetron reactive sputtering. The films were deposited onto Si(100) substrates with a power of 300 W at room temperature. The reactive gas was introduced up to 10% ($O_2$/(Ar + $O_2$)) during deposition, and the $Co_{39}Fe_{34}Hf_{9.5}O_{17.5}$ thin film exhibit excellent soft magnetic properties : saturation magnetization ($4{\pi}M_s$) of 19kG, magnetic coercivity ($H_c$) of 0.37 Oe, anisotropy field ($H_k$) of 48.62 Oe, and an electrical property is also shown to be as high as 300 ${\mu}{\Omega}cm$. It is assumed that the good soft magnetic properties of $Co_{39}Fe_{34}Hf_{9.5}O_{17.5}$ thin film results from high electrical resistivity and large anisotropy field.

• Proceedings of the Korean Magnestics Society Conference
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• 2014.11a
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• pp.33-33
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• 2014

• Journal of Magnetics
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• v.22 no.2
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• pp.275-280
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• 2017

A magnetic-field tunable 2.4 GHz microwave bandpass filter having insertion loss < -5dB on an FR4 substrate with the flaky magnetic material was designed and characterized. The tunability in the designed bandpass filter was achieved by adhering soft magnetic materials on top of the device. This soft magnetic material can be composed of ferromagnetic substance or ferrimagnetic substance. The performance of the designed bandpass filter under its influence is investigated. The frequency offset ratio changes over 30 %. There is over 20 % change in the center frequency towards the lower frequency region due to this application. These magnetic material layers achieved the center frequency shift and bandwidth extension without actually changing the original structure of the device.

• Proceedings of the Korean Powder Metallurgy Institute Conference
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• 2006.09b
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• pp.1169-1170
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• 2006

We made a high-speed motor and a DC brush-less motor for factory automation (FA) to investigate applicability of powder magnetic core to motor application, and compared those performances with the similar motors having conventional electro magnetic steel core. Permeability and saturated magnetization of powder magnetic core are less than those of elect romagnetic steel core, however output performances of each core motor are almost the same. The FA motor with powder magnetic core using three-dimensional magnetic circuit showed higher torque than the same volume motor with electromag netic steel core.

• Journal of Magnetics
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• v.18 no.3
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• pp.339-341
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• 2013

The magnetic field standards, facilities and capabilities available at NPL for the calibration of magnetometers and gradiometers and the measurement of the magnetic properties of materials will be introduced. The details of the low magnetic field facility will be explained and the capabilities this facility enables for the characterisation and calibration of ultra-sensitive room temperature magnetic sensors will be presented. Building on core material capabilities that are compliant with the IEC 60404 series of written standards, the example of a standard permeameter that has been modified for the measurement of strips for real world conditions is discussed. This was incorporated into a stress machine to measure the DC properties of the soft magnetic materials used by the partners of a collaborative industry led R&D project at stress levels of up to 700 MPa. The results for three materials are presented and the changes in the properties with applied stress compared to establish which material exhibits favourable properties.

• Journal of Magnetics
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• v.16 no.2
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• pp.177-180
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• 2011

0.30 mm thick and 90 mm wide thin foils made of Fe-6.5wt.%Si alloy were successfully fabricated by traditional rolling. The as-rolled sheets had good shapes and shining metal luster. The effects of annealing temperature on the magnetic properties of the sheets were investigated. Excellent Dc properties ($H_c$: 11.55 A/m, ${\mu}_m$: 23710, and $B_s$: 1.439 T) were obtained at an annealing temperature of 1453 K for 1.5 h. At low frequencies ($\leq$ 1 kHz), heat treatment temperature has little effect on iron loss which remained at the level of 9.8 W/kg. Annealing at 1273 K for 1.5 h is optimum for frequencies above 5 kHz.

• Journal of the Korean Electrochemical Society
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• v.8 no.3
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• pp.125-129
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• 2005

We have investigated the electrochemical factors affecting the magnetic properties of hard magnetic CoP nanowires and soft magnetic CoFe nanowires fabricated by ac electrodeposition into self-made AAO(anodic aluminum oxide) nano-templates. AAO template having nano scale pores of high aspect ratio has been prepared through 2-step anodizing of aluminum foil in sulfuric acid. Hard Magnetic properties of CoP nanowires were highly conditional on the applied ac potential which could be a decisive factor to make CoP nanowires made up of either pure hcp crystals or a mixture of hop crystals and fcc crystals. On the contrary to CoFe films, there was no anomalous codeposition in the electrodeposition of soft magnetic CoFe nanowires which exhibited their best saturation magnetization of 238 emu/g at the composition of $Co_{30}Fe_{70}$.

• Journal of Magnetics
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• v.14 no.3
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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.

• Proceedings of the Korean Powder Metallurgy Institute Conference
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• 2006.09a
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• pp.120-121
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• 2006

Magnetic properties of nanostructured materials are affected by the microstructures such as grain size (or particle size), internal strain and crystal structure. Thus, it is necessary to study the synthesis of nanostructured materials to make significant improvements in their magnetic properties. In this study, nanostructured Fe-20at.%Co and Fe-50at.%Co alloy powders were prepared by hydrogen reduction from the two oxide powder mixtures, $Fe_2O_3$ and $Co_3O_4$. Furthermore, the effect of microstructure on the magnetic properties of hydrogen reduced Fe-Co alloy powders was examined using XRD, SEM, TEM, and VSM.