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Volume 51, Issue 3
Displaying 1-12 of 12 articles from this issue
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Tsuneo Akashi2004 Volume 51 Issue 3 Pages 123-132
Published: March 15, 2004
Released on J-STAGE: May 22, 2009
JOURNAL FREE ACCESSDownload PDF (4419K) -
[in Japanese]2004 Volume 51 Issue 3 Pages 134
Published: March 15, 2004
Released on J-STAGE: May 22, 2009
JOURNAL FREE ACCESSDownload PDF (82K) -
Kiyotaka Yamauchi, Yoshijhito Yoshizawa2004 Volume 51 Issue 3 Pages 135-142
Published: March 15, 2004
Released on J-STAGE: May 22, 2009
JOURNAL FREE ACCESSRecently, soft magnetic alloys are used for many kinds of applications such as power electrical equipments and electronic appliances. Several ten years ago, only polycrystalline soft magnetic alloys were used for industrial usage. However, around 30 years ago, amorphous soft magnetic alloys produced by the rapid quenching technique were invented and have been developed. Around 15 years ago, nano-crystalline soft magnetic alloys were invented by the authors. This paper reports Fe-Si-Al alloys for the magnetic recording heads, Co-based amorphous alloys for switched mode power supplies, and nano-crystalline soft magnetic alloys with particular emphasis.View full abstractDownload PDF (5674K) -
Satoshi Hirosawa, Hirokazu Kanekiyo, Yasutaka Shigemoto, Toshio Miyosh ...2004 Volume 51 Issue 3 Pages 143-148
Published: March 15, 2004
Released on J-STAGE: May 22, 2009
JOURNAL FREE ACCESSThe continuous cooling curves during melt-spinning process of typical Fe3B/Nd2Fe14B-type nancomposite permanent magnet alloys Nd4Fe77.5-xTxB18.5 where T is Cr or Cu were measured using the infrared imaging technique and a continuous cooling transformation (CCT) diagram was constructed. The CCT diagram suggested that the effect of T was kinetic and phase selective. Effects of Ti and C additions on phase selection during rapid solidification were investigated in a Nd-poor and B-rich concentration region where the unfavorable Nd2Fe23B3 metastable phase becomes prevailing. The Ti-C addition was found to promote crystallization of Nd2Fe14B and prevents formation of γ-Fe. Utilizing this knowledge, a series of high coercivity Fe-B/Nd2Fe14B-type nanocomposite permanent magnets were developed on the basis of Nd-Fe-B-Ti-C system.View full abstractDownload PDF (2037K) -
Ken-ichi Machida, Takashi Horikawa, Masahiro Itoh2004 Volume 51 Issue 3 Pages 149-156
Published: March 15, 2004
Released on J-STAGE: May 22, 2009
JOURNAL FREE ACCESSFine ground powders of Nd-Fe-B sintered magnets (particle size = 46-125 μm in diameter) were coated and alloyed with Zn, Mg or Yb metal by sorbing them. For the sorption of Zn or Mg metal vapor, any effective recovery of magnetic properties of the ground powders was not observed. On the contrary, a significant recovery of the decreased magnetic properties of the ground powders was observed when the Yb metal was used as a sorbing material. The sorbing temperature and time for Yb metal vapor were optimized and after heating at 800°C for 90 min and annealing subsequently at 610°C for 60 min, the remanence (Br), coercivity (HcJ) and maximum energy product ((BH)max) values were increased to be 0.98T, 712kA/m and 173kJ/m3, respectively. From the microstructural characterizations of resulting samples, it was found that the sorbed Yb metal uniformly covered the surface and diffused to the grain boundary of fine powders forming a (Nd, Yb)Fe2 Phase. The Yb metal repairs the surface defects produced by grinding and oxidation. In addition, the surface of ground powders becomes smooth through the Yb metal sorption, so that the Hk/Hc value was improved.View full abstractDownload PDF (2326K) -
Tooru Obata, Futoshi Kuniyoshi, Yuji Kaneko2004 Volume 51 Issue 3 Pages 157-159
Published: March 15, 2004
Released on J-STAGE: May 22, 2009
JOURNAL FREE ACCESSIt is well known that the coercivity of Nd-Fe-B sintered magnets is easily influenced by varieties of grain boundary phases and the coherency between the Nd2Fe14B (T1) grains and grain boundaries. Moreover, the heat treatment after sintering is much effective to improve the coercivity. Therefore, it is important to elucidate the reaction between Nd2Fe14B grains and those grain boundary phases. In this paper, we tried to analyze the reaction of the Nd2Fe14B grains and grain boundary phases through a measurement of thermal expansion behavior of Nd-Fe-B sintered magnets, in which the addition of Co, Cu and Al are discussed to the ternary Nd-Fe-B sintered magnets. From our observations, it seems that the thermal expansion behavior shows the solid solubility of additives to Nd2Fe14B grains and also the melting reaction of grain boundary phases.View full abstractDownload PDF (1718K) -
Ken-ichi Machida, Masahiro Itoh, Masahiro Masuda, Seiji Kojima2004 Volume 51 Issue 3 Pages 160-164
Published: March 15, 2004
Released on J-STAGE: May 22, 2009
JOURNAL FREE ACCESSSome nickel coated Nd-Fe-B sintered magnet scraps were recycled as the starting materials for isotropic bonded magnets by using the melt-spinning method. Good magnetic properties (Br=-0.74T, Hcj=-0.94MA/m, and (BH)max=-86.5 kJ/m3) were obtained when the amorphous-like samples prepared at the roll surface velocity of 25 m/s were annealed at 973 K for 3 min in Ar. The magnetic properties were still improved by adding iron metal to the starting material scraps due to the further increase in the intrinsic magnetization of recycled samples. The magnetic properties of bonded magnets prepared from the above powders at 1 GPa were Br=-0.69T, Hcj=-0.81 MA/m, and (BH)max=-73.8 kJ/m3, which were nearly similar to those of the bonded magnet prepared from the commercially available powder with the magnetic properties of Br=-0.73T, Hcj=-0.79 MA/m, and (BH)max=-85.9 kJ/m3. Moreover, the nano-composite powders were prepared by hydrogenation disproportionation and subsequent oxidation of the slugs, which were generated during the recycling process by the melt-spinning. The resultant composite materials showed good absorption properties for the electromagnetic waves in 5-5 GHz range.View full abstractDownload PDF (386K) -
Shunro Nagata, Yoshihito Tachi, Mitsuyoshi Mastusita, Sigenori Matusak ...2004 Volume 51 Issue 3 Pages 165-171
Published: March 15, 2004
Released on J-STAGE: May 22, 2009
JOURNAL FREE ACCESSKawatetsu Mining Company Ltd. has developed large sized Mn-Zn ferrite single crystals mainly usea as me magnetic heads of the Video Tape Recorder, by innovating the structure of the 3 heater zone vertical Bridgman furnace and by optimizing the growth conditions. The weight of the single crystal is 28 kg, which is 110 mm in diameter and 630 mm in length, approximately 7 times as heavy as those conventionally supplied.
Distinctive features of the developed Mn-Zn ferrite single crystal are the uniformity of the composition within +/-0.5 mol%, lower included platinum particles in the crystal and elimination of cracks along with almost the full length of the crystal. In this report, the control of the variation of the composition along with the growth direction, the restriction of the dissolution of the platinum in melt and the suppression of the cracks, which had been main problems to be overcome during the development, are described.View full abstractDownload PDF (4870K) -
Hidenobu Umeda, Taku Murase, Takeshi Nomura2004 Volume 51 Issue 3 Pages 172-177
Published: March 15, 2004
Released on J-STAGE: May 22, 2009
JOURNAL FREE ACCESSLow-temperature sintering Y-type hexagonal femtes were made by the ceramics method. The temperature obtaining a single phase shifted lower with the CuO content. In Ba2Co1.0Cu1.0Fe12O22, a single phase was obtained at 950°C calcination. At the same time, the shrinkage curve shifts to the low temperature, and the firing temperature that is able to get over 95% of the theoretical density has lowered from 1200°C to 1000°C by the CuO substitution. Further more, Bi2O3 addition shifted the shrinkage curve to the low temperature. Exact sintered body with 900°C sintering was obtained by 5 wt% addition. The permeability and resonance frequency were 2.3 and 5.7 GHz respectively. The permeability was improved by divalent metal substitution, Ba2Me1.0Cu1.0Fe12O22 (Me: Ni, Mg, Zn), and the highest permeability was achieved by Zn substitution. The permeability and resonance frequency were 9.7 and 1.0 GHz respectively. It is found that Ba2ZnxCu2-xFe12O22 with Bi2O3 addition show high performance as magnetic material for chip inductors.View full abstractDownload PDF (2117K) -
Keisuke Matsuno, Keisuke Mizuno, Shigeki Nakagawa2004 Volume 51 Issue 3 Pages 178-183
Published: March 15, 2004
Released on J-STAGE: May 22, 2009
JOURNAL FREE ACCESSThin films of various kinds of hexagonal Magneto-plumbite type (M-type) ferrites as magnetic layer with Pt underlayer were prepared using flash annealing process. M-type strontium ferrite with substitution of Sr2+ and Fe3+ by La3+ and Co2+ thin films (LaCo-SrM) and M-type barium ferrite thin films (BaM) on Pt underlayer were prepared by the Facing-Targets Sputtering system. Since the grain size became huge enough because the high substrate temperature, e.g. around 500°C, is maintained particles by excess heating during the deposition. Flash-annealing technique means to anneal the specimen at high temperature above 900°C for a few moments after the deposition of the films at low temperature of 250°C enough for preventing crystallization. Annealing at 900°C for 3 minutes was an appropriate processing condition as a flash-annealing process to attain high perpendicular coercivity Hc⊥ and perpendicular squareness S⊥ ratio in case of BaM with maintaining the grain size as low as several tens nanometers. 30 nm-thick LaCo-SrM films prepared by flash-annealing at 900°C and for 5 minutes exhibited very smooth surface and small particle size about 22 nm. The film revealed large Hc and squareness of 4.5 kOe and 0.75, respectively. Flash-annealing is very useful for preparing the superior magnetic recording media.View full abstractDownload PDF (2568K) -
Setsuo Yamamoto, Kazuhiro Harada, Shinji Yamamoto, Hiroki Kurisu, Mits ...2004 Volume 51 Issue 3 Pages 184-189
Published: March 15, 2004
Released on J-STAGE: December 04, 2009
JOURNAL FREE ACCESSInductors with a Ni-Zn ferrite thin-film prepared by reactive ECR sputtering as a lower magnetic core and a Ni-Zn-Cu ferrite over coat layer as a upper magnetic core was designed using high frequency electromagnetic simulation based on FEM and fabricated in trial. The fabricated inductor with upper and lower magnetic cores showed higher inductance by about 25% than the inductor without magnetic core as predicted by simulation. High inductance value of the inductor with upper and lower magnetic cores was maintained up to high frequency of 1 GHz showing the effectiveness of the ferrite layers.View full abstractDownload PDF (2146K) -
Setsuo Yamamoto, Hirofumi Kuniki, Hiroki Kurisu, Mitsuru Matsuura, Pyu ...2004 Volume 51 Issue 3 Pages 190-194
Published: March 15, 2004
Released on J-STAGE: May 22, 2009
JOURNAL FREE ACCESSAmorphous Y-Fe-O thin films with a thickness of 2.6-2.8μm were deposited on GGG (111) substrates at 400°C using reactive RF magnetron sputtering method with Y2.84Fe5.16O12 ferrite sintered target. After that, the thin films were post-annealed in air at temperatures higher than 650 degrees Celsius for various hours to crystallize. In the XRD experiment, diffraction peaks from (888) plane were observed in the post-annealed samples. This showed that the films have been grown in hetero-epitaxial manner on GGG (111) substrate. The YIG ferrite thin films have low coercivity of less than 3 Oe and small ΔH of around 70 Oe. The YIG thin films are promising to be used in ultra thin isolators.View full abstractDownload PDF (371K)
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