Magnetic interaction effects on the magnetic switching volume for Cr/CoSm/Cr magnetic films deposited with different sputtering pressures (7~10 mTorr) of underlayer (Cr) was investigated. The magnetic interaction mechanism of all the Cr/CoSm/Cr magnetic films investigated in this study was dipole interaction, and the dipole interaction was stronger at the samples fabricated at low sputtering pressure. The magnetic field (H_ΔM) at which the maximum dipole interaction occurred in each sample was larger than the coercivity (H_c). The magnetic switching volume was larger for the sample with stronger dipole interaction, and it showed maximum value in the H_ΔM region and then decreased in higher field region above the H_ΔM. Therefore, it is considered that the intensity of the dipole interaction is closely related to the magnetic switching volume.

Ni_xZn_{1 − x}Fe₂O₄ (x = 0.4, 0.5, 0.6) spinel ferrites were prepared by sol-gel method using precursors of Ni(NO₃)₂ · 6H₂O, Zn(NO₃)₂ · 6H₂O, and Fe(NO₃)₂ · 9H₂O. Crystalline spinel phase were confirmed by X-ray diffraction (XRD) analysis for all the samples synthesized at T ≥ 400 ℃. Scanning electron microscope (SEM) was used for the study of microstructure. The average crystalline size increases from 17.6 nm to 96.2 nm with increasing synthesis temperature from 400 ℃ to 1000 ℃ for the Ni_0.5Zn_0.5Fe₂O₄. Sintering process was conducted at 1000 ℃ and 1250 ℃, respectively, on Ni_xZn_{1 − x}Fe₂O₄ (x = 0.4, 0.5, 0.6) samples synthesized at 400 ℃. B-H curve and complex permeability measurements were performed on these samples and the effect of composition, sintering temperature on the magnetic properties were investigated.

The scoria samples is analyzed six regions formed in the several parasitic volcano in Halla Mt. on the Jeju Island. These samples is investigated for iron oxide, mineral compositions and magnetic properties by the XRD, XRF and Mössbauer spectroscopy. The results are SiO₂ is 42.74~48.69 wt%, Na₂O+K₂O is 4.41~5.76 wt%. These tapes are the tephrite basanlte, trachybasalt and basalt. The main minerals are quartz, anorthoclase, albite and diopside. Also, we can see the iron compounds such as olivine, ilmenite, hematite, magnetite. According to Mössbauer spectroscopy on these iron compounds and most are composed of hematite and magnetite, which showing the hyperfine field. Fe³⁺/Fe_tot. ratio was analyzed as 59.70~75.60%, which is analyzed around Mt. Halla cinder cones higher than the value of the other site. Therefore, this sample were able to estimate that the formation at different points in time. The area ratio between the two sixtets is smaller than 2, which is the result of overlapping maghemite, hematite, and magnetite spectra that are not clearly distinguished at room temperature.

Power absorption of the composite composed with nonmagnetic polymer matrix and magnetic nano-particles were evaluated by the IEC standard. To investigate the effects of magnetic particle alignment on the power absorption, permeability of the composites were calculated along with alignment directions. Low fmr resonance frequency and high permeability values were shown for easy direction while high fmr resonance frequency and low permeability values were shown for hard direction. It was clearly shown that power absorption characteristics resembled the profiles of permeability for each alignment direction.

The magnetic field dependence of magnetic bead signals were measured by planner Hall resistance (PHR) and self-field (SF) methods by using PHR sensor. The bead signals of ΔPHR/PHR_o measured with PHR method and ΔSF/SF_o measured with SF method showed high hysteresis and low stability at H < H_eff, which was due to the hysteresis of the magnetic materials of NiFe/Cu/MnIr used in PHR sensor. While, the bead signals measured at H > H_eff showed very stable and ΔSF/SF_o showed maximum 14 times improved signal properties than ΔPHR/PHR_o. The stable bead signals measured by SF method at H > 2H_eff can be used to the biosensor.

In the case of single-phase SRM, values of minimum inductance are larger than that of the poly-phase SRM because the all stator poles of single-phase SRM are used as the magnetic flux path, while values of minimum inductance of the poly-phase SRM are almost unchanged. In addition, the segmental rotor type single-phase SRM has a cylindrical rotor, so that values of minimum inductance are larger than that of a conventional single-phase SRM with a salient rotor. This leads to a reduction in the generated torque. In this paper, This paper proposes a magnetic structure to minimize the variation of the minimum inductance by changing the shape of the rotor segment of segmental rotor type single-phase SRM and analyze it. This segmental rotor type single-phase SRM was analyzed by FLUX2D, a finite element analysis program.

A compelling need for high magnetic properties led to active consideration of rare-earth permanent magnets, which have been used in various applications such as communication, memory, and audio equipment. Recently, the use of rare-earth permanent magnets has expanded to green automobiles, robots, wind power plants, actuators, and generators due to the rise of the fourth industrial revolution and problematic issues of air pollution and fine dust generation. In particular, demand for high-performance permanent magnets is rapidly increasing to meet the ever growing interest in the industry of environment-friendly automobiles (hybrid/electric vehicles). However, since the rare-earth magnets are expensive and have limitation in high-temperature applications such as an automobile motor, it is essential to develop a permanent magnet with reduced rare-earth concentration that can bear high temperatures. Consequently, several major corporations have established a high-performance permanent magnet research team and are pursuing new businesses. At this point of view, the present article reviews a summary of the history and the R & D trends of rare-earth permanent magnets that have been developed in the past.