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Volume 53, Issue 3
March
Displaying 1-16 of 16 articles from this issue
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Paper
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Katsuhiko Ueda, Terufumi Machida, Kazuo Asaka2006 Volume 53 Issue 3 Pages 225-230
Published: 2006
Released on J-STAGE: August 18, 2006
JOURNAL OPEN ACCESSA two-step compacting process was developed to achieve the production of high-density Nd-Fe-Co-B/epoxy magnets. Because of its poor compressibility, the severity factor for compaction of Nd-Fe-Co-B magnetic powder reaches a high value of 6.10mm-1 due to its hardness and brittleness. However, by applying the developed method, magnets with a very high density of 6.41Mg/m3 can be fabricated. The second compaction step provides a densification effect on the pre-compacted body obtained in the first compaction step. The densification in the second step occurs through fracturing and stacking of the particles that rose up due to the large spring back during the first compacting and after the removing from the die. This new method enables for fabricated magnets with not only a high density which leads to excellent magnetic properties, but also excellent compressive strength and dimensional accuracy.View full abstractDownload PDF (855K) -
Susumu Handa, Yasuo Ohshima, Yousuke Nakasato2006 Volume 53 Issue 3 Pages 231-236
Published: 2006
Released on J-STAGE: August 18, 2006
JOURNAL OPEN ACCESSMagnetic properties and magnetic domains of MnZn ferrite cores by low temperature sintering were investigated. The powder was prepared using the conventional ball milling. The specimens were sintered at 900°C for 5 hours in reductive atmosphere. Grain growth of sintered cores got remarkable by adding above 0.05 wt% meta-boric lithium (LiBO2). The initial permeability including 0.05wt%LiBO2 was 2071. Magnetic domains were investigated by Laser microscope and SEM using magnetic colloid. Width of magnetic domains were smaller than a commercial MnZn high permeability core (Material spec. is 15000 at 10kHz). It was suggested that this core has compressive stress by magnetic domain observation.View full abstractDownload PDF (2653K) -
Susumu Handa, Yasuo Ohshima, Yousuke Nakasato2006 Volume 53 Issue 3 Pages 237-241
Published: 2006
Released on J-STAGE: August 18, 2006
JOURNAL OPEN ACCESSMagnetic properties and magnetization process of MnZn ferrite cores by low temperature sintering were investigated. The powder was prepared using the conventional ball milling. The specimens were sintered at 900°C for 5 houres in reductive atomosphere including CO2 and H2. The flow rate H2/CO2 was the best between 1 and 2%. The initial permeability was 2379 at 100kHz, 0.5V.
Magnetization process was observed by Bitter method. Wide width magnetic domains (180°domain) were easier magnetized than narrow one. On the other hand, 90°domains did not change the width with increasing magnetic field.View full abstractDownload PDF (1757K)
Special Issue:New Applications and Evaluation Methods of Magnetic Materials
Summarization
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Yohtaro Yamazaki2006 Volume 53 Issue 3 Pages 244
Published: 2006
Released on J-STAGE: August 18, 2006
JOURNAL OPEN ACCESSDownload PDF (138K)
Memorial Lecture of JSPM Award
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Ken Makita, Shigeru Takaki2006 Volume 53 Issue 3 Pages 245-250
Published: 2006
Released on J-STAGE: August 18, 2006
JOURNAL OPEN ACCESSDegree of preferred orientation was evaluated at three stages in manufacturing sintered magnets such as Nd-Fe-B and Sr-ferrite. In magnetization stage, magnetization curves of raw powder were measured by vibration sample magnetometer, which suggested that rotation of particle started after technical magnetic saturation of the particle has completed. A rod-like structure with a diameter of few hundreds of microns was formed along the direction of applied field in case of Nd-Fe-B powder. In consolidation stage, the homogeneity of compaction was investigated visually by means of marker layers set parallel to the direction of applied field. The alignment was disordered locally in the vicinity of dies. Alternate movement of upper punch and lower one was effective to eliminate the disorder. As for sintering stage, degree of preferred orientation was evaluated quantitatively from data of X-ray pole figure measured not only for sintered samples but also for green compacts. Degree of preferred orientation of green compacts always increased after sintering, presumably because small and incompletely oriented particles were absorbed to larger and correctly oriented ones as a result of the grain growth in the sintering stage.View full abstractDownload PDF (1214K) -
Satoshi Sugimoto, Toshio Kagotani, Toru Maeda2006 Volume 53 Issue 3 Pages 251-257
Published: 2006
Released on J-STAGE: August 18, 2006
JOURNAL OPEN ACCESSRecently, the use of microwaves in the GHz range has increased because of the demand for large data transmission. However, the problem of electromagnetic interference (EMI) has become serious, and much attention has been paid to microwave absorption materials. We have investigated magnetic loss of permanent magnet materials at natural resonance frequency, and have succeeded in the development of microwave absorbers using M-type (or W-type ferrite) and RE-Fe-B (RE: rare earth) compounds. The resonance frequency can be controlled by substitution of Fe3+ ion with other metal ion in the M-type or W-type ferrite. The resin composite of M-type ferrite shows wide bandwidth, in which the reflection loss (R.L.) is less than −20 dB. In the RE-Fe-B compounds, the substitution of RE with Sm or the fabrication of nanocomposite with a soft magnetic phase is effective method for controlling their resonance phenomena and functional frequency as microwave absorbers. The powder with fine α-Fe structure, which is produced by the disproportionation reaction of RE-Fe compounds, is useful for the filler of resin composite microwave absorbers in several GHz range.View full abstractDownload PDF (778K)
Paper
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Satoshi Sugimoto, Toru Hirayama, Tomohito Maki, Toshio Kagotani, Koich ...2006 Volume 53 Issue 3 Pages 258-262
Published: 2006
Released on J-STAGE: August 18, 2006
JOURNAL OPEN ACCESSEffect of an applied field during film deposition on magnetic properties of aerosol-deposited (AD) Sm-Fe-N films was investigated. By aligning the two magnets with facing the opposite poles, a magnetic field of 0.15 T can be applied perpendicular to the film. The thickness of AD film decreased with increasing applied field. However, relatively large thickness of 94 μm was obtained at 0.15 T. The remanence measured in the perpendicular direction increased from 54.5 to 61.3 Am2/kg by applying magnetic field. In the case of using a solenoid coil, a magnetic field of 0.21 T can be applied perpendicular to the film. The thickness of AD film also decreased, however, the AD film shows thickness of 65 μm at 0.21 T. The remanece in the perpendicular direction increased from 54.5 to 58.6 Am2/kg with increasing applied field. Therefore, it is concluded that the AD film can be oriented perpendicular to the film plane by applying a magnetic field and show high remanence with maintaining large thickness.View full abstractDownload PDF (622K) -
Kenji Kamishima, Chiaki Ito, Koichi Kakizaki, Nobuyuki Hiratsuka2006 Volume 53 Issue 3 Pages 263-267
Published: 2006
Released on J-STAGE: August 18, 2006
JOURNAL OPEN ACCESSTi-Zn substituted hexagonal ferrite samples Ba3Co2TixZnxFe24-2xO41 with 0<x<4 have been prepared by a conventional ceramic method. Ba3Co2TixZnxFe24-2xO41 with x=0 and 1 had a major phase of Z-type. However, other phases of M-type, Y-type, and spinel-type ferrites were observed for the samples with x=2 and 4. For the specimens with x=0 and 1, the initial permeability increased with an increase of the sintering temperature from 1250 to 1300°C. This may be attributed to the densification and the grain growth. For the specimens having x in the range from 0.0 to 1.0 sintered at 1250°C, the saturation magnetization was almost independent of x, the relative density took a maximum at x=0.85, and the coercivity had a minimum around x=0.85. Additionally, the maximum permeability of 24 was also attained at the composition. It was likely that these variations were related to the enhancement of the ferrite formation and densification with a partial substitution of Zn2+-Ti4+.View full abstractDownload PDF (703K) -
Hitoshi Matsuura, Kenji Kawano, Kenji Kamishima, Koichi Kakizaki, Nobu ...2006 Volume 53 Issue 3 Pages 268-272
Published: 2006
Released on J-STAGE: August 18, 2006
JOURNAL OPEN ACCESSY-type (Ba2Zn2Fe12O22; Y), M-type (BaCo1.1Ti1.1Fe9.8O19; MCT) and mixture of these hexagonal ferrites (Y+xMCT; x=0∼3) were prepared by the conventional solid-state reaction approach. Samples were made with BaCO3, ZnO, CoO, TiO2 and α-Fe2O3 as starting materials. The frequency dependence of the initial permeability of all samples was measured using an impedance analyzer (HP4291B). The initial permeability of Ba3Zn2Co1.1Ti1.1Fe21.8O41 (x=1) was 23 (at 100MHz), which is the highest value in this study and the Snoek's product of this sample has been reached to 14.7GHz. This value is twice larger than that of Zn2Y. The detailed analysis of frequency dependent permeability curves for these samples strongly suggests that this enhancement of the Snoek's product is due to the change of magnetic anisotropy caused by the substitution of Co2+ and Ti4+ ions for Fe3+ ions.View full abstractDownload PDF (645K) -
Takuya Aoki, Hidenobu Umeda, Kensaku Asakura, Taku Murase2006 Volume 53 Issue 3 Pages 273-276
Published: 2006
Released on J-STAGE: August 18, 2006
JOURNAL OPEN ACCESSWith the miniaturization of electronic devices, ferrites with high mechanical strength are demanded. In this paper, the effect of SiO2 on the bending strength of NiCuZn ferrite was investigated. It has been found that the bending strength of NiCuZn ferrite was increased the addition of SiO2. The NiCuZn ferrite with SiO2 addition showed a structure with smaller and more uniform grain size than non-addition. As a result of analysis, Si exists in the same position as Zn, suggesting the formation of Zn2SiO4. The thermal expansion coefficient of Zn2SiO4 is lower than that of ferrite. The improvement in the bending strength of NiCuZn ferrite are attributed to the control of grain growth by Zn2SiO4 and the residual stress caused by the difference of coefficients of liner thermal expansion between ferrite phase and Zn2SiO4 phase.View full abstractDownload PDF (610K) -
Pei Bian, Dong-Ying Ju2006 Volume 53 Issue 3 Pages 277-281
Published: 2006
Released on J-STAGE: August 18, 2006
JOURNAL OPEN ACCESSNiCuZn ferrite has been widely applied to multilayer chip inductors in recent years. While fabricating the multilayer structure of ferrite and metal alternatively, it is requested to simultaneously sinter in low temperature for the internal conductor Ag (Melting point 960°C) and ferrite materials. The purpose of this study is to fabricate the NiCuZn ferrite sintered body with high-strength and high-frequency magnetic property. The procedures are as follows: firstly, the NiCuZn ferrite powder was synthesized under a CO2 atmosphere at 500°C from the mixed doxalate which was synthesized by liquid phase deposition method from mixed metal chloride and ammonium oxalate; subsequently, a small amount of boric acid [H3BO3] was added to the powder, and then the NiCuZn ferrite powder compact was formed with Newton press and CIP methods; finally, the NiCuZn ferrite sintered body was fabricated by sintering at 900°C under a CO2 atmosphere. Through the experiments of high temperature shrinkage, evaluation of mechanical strength and magnetic property, NiCuZn ferrite fabricated by this study can present good characters on high frequency and high mechanical strength when the sintering temperature and boric acid additive are 900°C and 0.5 mass%, respectively.View full abstractDownload PDF (644K) -
Daisuke Harimoto, Yutaka Matsuura, Seiichi Hosokawa2006 Volume 53 Issue 3 Pages 282-284
Published: 2006
Released on J-STAGE: August 18, 2006
JOURNAL OPEN ACCESSGrain alignment is one of a factor affecting coercive force in Nd-Fe-B sintered magnets. Relation between degree of alignment and coercive force was evaluated using Br/Js as the degree of grain alignment. It was found that the coercive force decreases with alignment increase in highly aligned region. The decrease ratios of coercive force with various alignments to the isotropic magnet's coercive forces are on the same line even though they have different coercive force due to different composition in isotropic aligned state. Extrapolating this line to perfectly aligned magnet, coercive force of perfectly aligned magnet reaches to −30% of coercive force of the isotropic oriented magnets.
It is found that this coercive decrease ratio behavior is similar even in ferrite magnets. We estimate coercive force of perfectly aligned magnets from isotropic magnet and obtained 1/√2 (0.70) of isotropic magnet's coercive force which is agrees well to our experimental result.View full abstractDownload PDF (284K) -
Ryoji Nakayama, Muneaki Watanabe, Gakuji Uozumi, Kazunori Igarashi, Ko ...2006 Volume 53 Issue 3 Pages 285-289
Published: 2006
Released on J-STAGE: August 18, 2006
JOURNAL OPEN ACCESSTo decrease the hysteresis losses of soft magnetic composite (SMC) cores, it is effective that the coercivity of cores is reduced by the high temperature stress relieving annealing to the green compacts. It is reported about magnetic properties of SMC, which MgO system evaporation insulation coating on the surface of iron powders had greater heat-resistance than the conventional phosphate insulation coating. We found that it can be obtained new SMC core with lower iron loss made from iron powders with evaporated MgO insulation coating. The iron loss of them at 50 Hz for Bm = 1.5 T was lower 30% of the conventional SMC core and was almost the same with the laminated steel (50H600) core. It became clear that typical MgO insulating films had microcrystallines have the thickness of about 50 nm and enough heat resistance.View full abstractDownload PDF (932K) -
Shin Tajima, Mikio Kondoh, Takeshi Hattori, Hidefumi Kishimoto, Masaki ...2006 Volume 53 Issue 3 Pages 290-296
Published: 2006
Released on J-STAGE: August 18, 2006
JOURNAL OPEN ACCESSWe have developed new powder magnetic cores with high densities from iron particles coated with new type of phosphate glass insulator of Sr-B-P-O system, which was named HDMC (High Density Magnetic Composite). They exhibit high magnetic flux density, high mechanical strength and high resistivity. To improve the properties of the HDMC, effects of addition of organic compounds to Sr-B-P-O insulator were investigated. Additon of benzotoriazole and 1, 10 phenantroline was found to increase resistivity of the HDMC. The HDMC with addition of 0.05mass% benzotriazole, which was made by compaction at 1176MPa and heat treatment at 773 K, showed following properties; density of 7.70 Mg/m3, magnetic flux densities of 1.18 T at 2 kA/m and 1.70 T at 10 kA/m, Hc of 300 A/m, resistivity of 200 μΩm, radial crushing strength of 110 MPa, and iron loss (at Bmax = 1 T, f = 400 Hz) of 400 kW/m3.View full abstractDownload PDF (742K) -
Masateru Ueta, Satoshi Uenosono, Naomichi Nakamura, Junichi Asami2006 Volume 53 Issue 3 Pages 297-303
Published: 2006
Released on J-STAGE: August 18, 2006
JOURNAL OPEN ACCESSThree types of rotors were made and installed into a commercial brush DC motor. Motor performances were measured to know the effects of magnetic properties of rotor materials. The materials used as a rotor were two types of iron powder cores with flux densities of 1.60T or 1.70T at 10 kA/m and a lamination steel (SPCC) core with a flux density of 1.82T, respectively. The efficiencies of the iron powder motors were 68% or 70% and that of the lamination steel motor was 64%, therefore the motor efficiency was improved by about 6%. Two types of iron powder motors and the lamination steel motor gave almost the same output torques at the speeds of 4,250 to 5,350 rpm, although the flux densities of the iron powder cores were smaller than that of the lamination steel core. These results indicated that the iron powder cores enhanced the performances of the brush DC motor.View full abstractDownload PDF (1573K)
Errata
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2006 Volume 53 Issue 3 Pages 845-850
Published: 2006
Released on J-STAGE: November 10, 2006
JOURNAL OPEN ACCESSWrong:in the 10th line and the 20th line
Right:in the 10th line and the 20th lineView full abstractDownload PDF (21K)
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