日本応用磁気学会誌
Online ISSN : 1880-4004
Print ISSN : 0285-0192
ISSN-L : 0285-0192
28 巻 , 3 号
選択された号の論文の55件中1~50を表示しています
論文
  • 杉田 龍二, 小峰 啓史, 村野井 徹夫, 西川 正一, 安永 正, 長尾 信
    2004 年 28 巻 3 号 p. 231-234
    発行日: 2004年
    公開日: 2006/11/24
    ジャーナル オープンアクセス
    Dependence of magnetic contact duplication properties on magnetic layer thicknesses of master media was studied. We found from experiments that for a master medium with a bit length of 2.5μm, sufficient duplication was attained if the thickness was 1μm, whereas for a bit length of 10μm, a thickness of 1μm or more was necessary to obtain sufficient duplication. We simulated duplication properties for bit lengths of 2.5 and 10μm using the finite element method, in addition to performing the experiments. The simulated results agreed well with the experimental ones. Because of this agreement, simulations were carried out to study shorter bit lengths; these simulations showed that for master media with bit lengths of 0.1 and 0.5μm, duplication properties are unchanged over thicknesses of 0.04 and 0.1μm, respectively.
  • 立花 淳一, 水野 裕, 伊藤 琢哉, 蟻坂 裕一
    2004 年 28 巻 3 号 p. 235-240
    発行日: 2004年
    公開日: 2006/11/24
    ジャーナル オープンアクセス
    We investigated the relationship between the shape of clusters of Co crystallites, obtained by transmission electron microscopy (TEM), and the magnetic anisotropy field of grains (Hkgrain) of Co-CoO obliquely evaporated magnetic tape. Comparison of the former with the latter revealed that the Hkgrain of Co-CoO obliquely evaporated magnetic tape closely correlates with the aspect ratio (N) of clusters of Co crystallites. The magnitude of Hkgrain is defined as that of a magnetic field where the rotational hysteresis loss of the torque curve is zero. We investigated the relationship between the Hkgrain and saturation magnetization Ms, using samples prepared under various conditions. The results showed that Hkgrain becomes asymptotic to the value HkCo + Ms/2, determined by the maximum value of the shape anisotropy Ms/2 in the region of low Ms. The value of Hkgrain calculated by using a value of N obtained from TEM images was found to be close to the value of Hkgrain obtained by magnetic torque measurement, and this tendency was confirmed qualitatively.
  • 奥本 孝明, 松本 光功, 森迫 昭光
    2004 年 28 巻 3 号 p. 241-244
    発行日: 2004年
    公開日: 2006/11/24
    ジャーナル オープンアクセス
    NdFeB thin films with perpendicular c-axis orientation texture have been studied as promising candidates for ultrahigh-density recording media because of their high magneto crystalline anisotropy and large saturation magnetization. NdFeB thin films deposited on W underlayer with composition of Nd18Fe76B6 and a thickness of 15 nm exhibited perpendicular coercivity as high as 6.0 kOe. In our case, NdFeB thin films deposited on W underlayer need substrate temperatures of 440°C to crystallize Nd2Fe14B and to have high magneto crystalline anisotoropy. Reducing substrate temperature is instructive for sputtering process and decreasing grain size. It was found that Cu addition to NdFeB phase could be reduced the substrate temperature from 440°C to 380°C with 2.7 at.% of Cu. The perpendicular coercivity and squareness for NdFeB thin film with the thickness of 15 nm and 2.7 at.% of Cu were 4.7 kOe and 0.95, respectively.
  • 佐藤 公宣, 秦 高梧, 及川 勝成, 岡本 聡, 北上 修, 島田 寛
    2004 年 28 巻 3 号 p. 245-248
    発行日: 2004年
    公開日: 2006/11/24
    ジャーナル オープンアクセス
    Seeking new materials for high-density magnetic recording media, we investigated the magnetic anisotropy and phase separation of Co-Mo and Co-W binary alloy thin films. Both alloys exhibit much larger magnetic anisotropy than does Co-Cr. Thermodynamic calculations on phase equilibria of Co-X (X = Cr, Mo, W) binary systems predict that magnetically induced two-phase separation can occur in these binary alloys as has been experimentally observed in Co-Cr. In fact, their saturation magnetization and Curie temperature are obviously enhanced by annealing or depositing them at high temperatures, suggesting the promotion of two- (ferro/para) phase separation. Microscopic compositional modulation due to the phase separation was confirmed in a Co-Mo film by micro EDX analysis. However, the amplitude of the compositional modulation is much weaker than the thermodynamic calculations, indicating that the miscibility gap is considerably narrowed probably due to large misfit energy at the ferro/para interface or due to very limited diffusion constants of Mo and W.
  • 高井 充, 大川 秀一, 諏訪 孝裕, 中田 勝之, 森谷 誠
    2004 年 28 巻 3 号 p. 249-253
    発行日: 2004年
    公開日: 2006/11/24
    ジャーナル オープンアクセス
    The discrete track technology is promising as the technology that makes high track density. It decreases cross talk from the adjacent track because the track is separated in physically and magnetically by the grooves. However, the magnetic head does not fly stably on the disk with grooves. Therefore, it’s necessary to make smooth surface by refilling the grooves with non-magnetic material. We tried to flatten the discrete track media surface by using the bias sputtering method and the etching back method in dry process.
  • 及川 忠昭, 島津 武仁, 稲葉 祐樹, 佐藤 英夫, 青井 基, 村岡 裕明, 中村 慶久
    2004 年 28 巻 3 号 p. 254-257
    発行日: 2004年
    公開日: 2006/11/24
    ジャーナル オープンアクセス
    The magnetic properties and media noise performance of {(Co100-XCrX)100-YPtY}89-{SiO2}11/Ru media were investigated as functions of the Pt and Cr contents. The magnetic anisotropy energy Ku shows a broad maximum at a Pt content around Y = 20 at%, almost irrespective of the Cr content. The anisotropy energy of the grains, Kug, calculated by taking account of the volume fraction, reaches nearly 8 x 106 erg/cm3 even with a Cr content of X = 10 at%. The ratio of the magnetic anisotropy energy to the thermal energy, KuVact/kT, at this composition maintains a value of more than 100, oven with 10 nm thickness and a grain size of 7.7 nm, indicating a high potential to resist thermal agitation. The high Ku causes a largo remanence coercivity Hr and a loop squareness of 1 in the Pt content region around Y = 20. The activation diameter Dact increases gradually as the Pt content increases, while an increase of the Cr content reduces the Dact. The signal-to-media-noise ratio SNmR improves as the Pt content decreases, which accords well with the reduction in Dact. It is likely that a Pt content of Y = 15 - 20 at% is an optimum composition to attain both low media noise and high thermal stability. There is a trade-off between low noise performance and thermal stability as a function of the Cr content.
  • 鈴木 淑男, 大内 一弘
    2004 年 28 巻 3 号 p. 258-262
    発行日: 2004年
    公開日: 2006/11/24
    ジャーナル オープンアクセス
    Fe-based amorphous soft-magnetic films and Mn-Ir exchange-biasing films were investigated, with the aim of developing a soft-magnetic underlayer for L10-type Fe-Pt perpendicular double-layered media. It was found that a carbon-added Fe78Si9B13 composition film had a smooth surface and excellent structural stability in amorphous state after annealing at 450°C. A Bs value of 13.7 kG and an Hc value of below 1 Oe for the easy axis were obtained. For the exchange-biased films, the compositions and crystal orientations of the Mn-Ir films and the effects of inserting a Co-Fe layer between the Fe-Si-B-C layer and the Mn-Ir layer were investigated. As a result, a large unidirectional anisotropy constant, Jk, of 0.5 erg/cm2 was obtained for a layer configuration of Fe-Si-B-C (50 nm)/Co70Fe30 (5 nm)/Mn85Ir15 (10 nm)/Nb-Permalloy (5 nm)/Ta(20 nm)/glass-substrate. The large exchange-bias field, small coercivity, smooth surface, and excellent structural stability of the film will be suitable for the soft-magnetic underlayer of Fe-Pt media.
  • 吉川 裕紀, 中川 茂樹
    2004 年 28 巻 3 号 p. 263-266
    発行日: 2004年
    公開日: 2006/11/24
    ジャーナル オープンアクセス
    The magnetic properties of Co/Pd multilayers seem to be strongly dependent on the surface and interface morphology of the films. Microstructure of the multilayers can be tailored by controlling the process conditions. Effect of two process conditions: (1) changing number of periods and (2) insertion of Pd underlayer, has been studied. In both conditions we have found a common relationship between surface roughness Ra and α(=4π(dM/dH) @H=Hc). Increase of surface roughness caused large decrease of α due to the decoupling of exchange interaction among the grains. In order to confirm the effects of Co and Pd layer roughness, respectively, [Co/Pd]20 multilayers were deposited at different Ar gas pressures PAr for each layer. The M-H characteristics of the films with Pd layers deposited at low PAr didn’t reveal high coecivity Hc. AFM observation clarified that the deposition of Pd layers at high PAr enhances the surface roughness of the multilayers. It was found that a high PAr condition during Pd deposition is essential for high Hc.
  • 神藤 孝彰, 中 芳夫, 田嶋 大介, 白神 清民, 越本 泰弘
    2004 年 28 巻 3 号 p. 267-270
    発行日: 2004年
    公開日: 2006/11/24
    ジャーナル オープンアクセス
    We studied a two-input, two-output control system for an HDD requires a sensor to measure displacement between a VCM and a second-stage actuator We thus considered a displacement sensor using the optical lever method. To realize the displacement sensor, an LD and a PD were assembled to the head arm The fabricated sensor showed resolution of 15 nm and bandwidth of 30 kHz From these experimental results, we confirmed that it is possible to realize a measurement system that can detect accurately displacements in a hard disk enclosure.
  • 三宮 健, 遠藤 拓, 上坂 保太郎, 仲谷 栄伸, 林 信夫, 福島 宏
    2004 年 28 巻 3 号 p. 271-274
    発行日: 2004年
    公開日: 2006/11/24
    ジャーナル オープンアクセス
    We used computer simulation to examine an measuring method for easy axis distribution of a recording medium. Remanent magnetization Mr with the field applied in-plane showed that in-plane Mr increases with saturation magnetization Ms when the easy axis distribution is not random in plane, though Mr scarcely changes with Ms when the easy axis distribution is random in plane. We found that easy axis distribution perpendicular to the film plane does not affect in-plane Mr with the field applied in plane. We also found that easy axis distribution perpendicular to the film plane can be estimated from distribution of easy axis in plane, tilted direction of easy axis from the film plane, and perpendicular component of Mr with the field applied out of plane. Good agreements were obtained between experimentally derived remanent magnetization of VTR and audio tapes with the field applied out of plane and Mr derived from computer simulation.
  • 田口 香, 高橋 慎吾, 山川 清志, 大内 一弘
    2004 年 28 巻 3 号 p. 275-278
    発行日: 2004年
    公開日: 2006/11/24
    ジャーナル オープンアクセス
    In order to realize high-linear-density recording, transition shifts of recorded bits on a medium should be reduced. In perpendicular magnetic recording combined with a single-pole head and a double-layered medium, a difference in bit length between both polarities was observed, even for periodic recorded bits. It was caused by dc-erased magnetization on both sides of a recording track and an ambient dc-magnetic field. A dc-bias current recording method was able to eliminate the imbalance of the bit length. It was found that a lower NLTS could be obtained by using dc-bias current recording, than by using a conventional write pre-compensation method.
  • 経徳 敏明, 鈴木 淑男, 大内 一弘
    2004 年 28 巻 3 号 p. 279-282
    発行日: 2004年
    公開日: 2006/11/24
    ジャーナル オープンアクセス
    The relationship between the magnetic properties of Co-Cr-Pt film and the film’s surface morphology was investigated in terms of the differences in surface free energy and interatomic distance between the Co and the underlayers. It was found that high perpendicular coercivity was obtained in the film structure where it was flat and smooth and grain separation had begun to occur. Moreover, the surface free energy was found to be one of the factors controlling not only the film surface morphology, but also the crystal orientation.
  • 木谷 貴則, 駒木根 隆士, 本多 直樹, 大内 一弘
    2004 年 28 巻 3 号 p. 283-288
    発行日: 2004年
    公開日: 2006/11/24
    ジャーナル オープンアクセス
    The contribution of the M-H loop slope to the recording properties of double-layered perpendicular magnetic recording media was studied. Experimental results confirmed that the sharpness of the magnetization transition corresponded to the steepness of the M-H loop. The write sensitivity, S/N, and modulation overwrite also increased along with the recording resolution in media with steeper M-H loops. Though the nonlinear transition shift increased in media with an increased loop slope, the shift was dominated by the phase distortion, which could be minimized by phase precompensation.
  • 斉藤 伸, 橋本 篤志, 高橋 研, 迎 展彰
    2004 年 28 巻 3 号 p. 289-294
    発行日: 2004年
    公開日: 2006/11/24
    ジャーナル オープンアクセス
    We propose a noble stacked soft magnetic underlayer (SUL) with the so-called top-type pinning structure, which consists of a soft magnetic layer (SM layer) fabricated by plating and an antiferromagnetic layer (AFM layer) deposited by sputtering, on an Al/NiP disk. Through investigation of the structure and magnetic properties of this stacked SUL, we clarified the following points: (1) the thermal stability of NiFeP plated on an Al/NiP disk is 280°C, which is the crystallization temperature of the amorphous NiP layer; (2) to induce large unidirectial magnetic anisotropy in the SUL, it is necessary to introduce a soft magnetic buffer layer and apply dry etching to the NiFeP surface; (3) a unidirectional magnetic anisotropy field can be induced in an SM layer fabricated by plating as well as in one fabricated by sputtering, which results in the whole disk having a single-domain structure.
  • 斉藤 伸, 板垣 憲和, 高橋 研
    2004 年 28 巻 3 号 p. 295-300
    発行日: 2004年
    公開日: 2006/11/24
    ジャーナル オープンアクセス
    To combine “maintenance of thermal stability” and “magnetic isolation among magnetic grains” for CoCr-based perpendicular media, we focus attention on the post-annealing process. Significant improvement of the magnetic properties is confirmed for the post-annealed media utilizing titanium as both cap- and under-layers. In consequence it was found that a remarkable large coercivity of 9.1 kOe and squareness of 1 are realized for Ti/Co68Cr16Pt16/Ti post-annealed media; a non-ferromagnetic TiCoPt layer with B2 type structure is formed between the Ti and CoCrPt layers by post-annealing; and a remarkable improvement of the magnetic properties is caused by both magnetic isolation among magnetic grains and elimination of the nanocrystalline initial layer, which behaves like a soft magnetic layer.
  • 伊藤 琢哉, 清水 浩一郎, 蟻坂 裕一, 岩崎 洋, 村上 恭和, 進藤 大輔
    2004 年 28 巻 3 号 p. 301-304
    発行日: 2004年
    公開日: 2006/11/24
    ジャーナル オープンアクセス
    The mechanism for the preferred orientation of hcp-Co <001> in Co-CoO evaporated magnetic film promoted by a CoO underlayer was investigated. A preferred orientation relation, CoO <111>//Co <001>, was found in neighboring crystallites at the interface between the CoO underlayer and the magnetic layer. The angle between CoO <111> and Co <001> neighboring at the interface was measured in high-resolution electron microscopy (HREM) images. The mechanism is explained in terms of the preferred orientation relation.
  • 山田 裕基, 林 信夫
    2004 年 28 巻 3 号 p. 305-311
    発行日: 2004年
    公開日: 2006/11/24
    ジャーナル オープンアクセス
    The use of Newton’s method to solve the Landau-Lifshitz-Gilbert (LLG) equation discretized according to the Crank-Nicolson method is examined from the viewpoint of accuracy and computation time. Magnetization reversal and Bloch wall motion in a thin Permalloy film were calculated as an example. Although the convergence speed of Newton’s method is high, the solution of simultaneous algebraic equations requires a computation time of O(N3) in principle, when we denote the numbers of computing cells as N. If we take only the nearest-neighbor magnetostatic interaction into consideration in the implicit treatment, the coefficient matrix for the algebraic equation and the computation time are reduced to tridiagonal and O(N), respectively, in the case of one-dimensional calculation. Newton’s iteration can be repeated several times without increasing the order of computing time since the time required to calculate the demagnetizing field is O(N log N) if we use FFT. On detailed comparison with the Runge-Kutta method, a typical method for ordinary differential equations, the proposed method is found useful from the viewpoint of time-step dependence of numerical error and reliability.
  • 稲垣 明, 恒岡 雅也, 大島 敦, 小林 正, 藤原 裕司, 塩見 繁, 白鳥 力
    2004 年 28 巻 3 号 p. 312-317
    発行日: 2004年
    公開日: 2006/11/24
    ジャーナル オープンアクセス
    This paper reports the magnetic and magneto-optical properties of antiferromagnetic exchange coupled (AFC) RE-TM double layered films prepared by sputter deposition. The sample structure is glass/underlayer Ru/Gd-Fe-Co/(E-layer Fe-Co)/AFC layer Ru/(E-layer Fe-Co)/Gd-Fe-Co/protectivelayer Ru. The exchange coupling energy J was found to depend on Ru thickness of the AFC layer. The first AFC peak was found at an AFC layer thickness of 3.0 Å. Next we inserted a thin Fe-Co layer called the “E-layer,” between the AFC layer and the magnetic layer to improve the J value. In AFC RE-TM double layered films, a complicated Kerr loop was observed when each magnetic layer was thin. Then we compared the calculated result with the experimental result to distinguish the ferromagnetic coupling from the AFC. Next we investigated thermal stability of J. Moreover we calculated the magneto-optical properties with the film structure of DWDD, using AFC RE-TM double layered films for the displacement layer.
  • 塚本 新, 中川 活二, 伊藤 彰義, Kirilyuk Andrei, Rasing Theo, 粟野 博之
    2004 年 28 巻 3 号 p. 318-321
    発行日: 2004年
    公開日: 2006/11/24
    ジャーナル オープンアクセス
    This paper describes results of a time-resolved study of the ultrafast magnetic response of Gd23.1Fe71.9Co5.0 MAMMOS structures under conditions near actual read temperature. An all-optical pump and probe method was used, in which an intense (pump) light beam excited a medium due to ultrafast laser heating and a less intense (probe) beam monitored this photo-excited state through the magnetooptical Kerr effect. Our experiment clearly demonstrates that the photo-excitation effectively excites coherent spin waves in the magnetic material. Precession frequencies of several GHz and relaxation times in the nanosecond range were observed.
  • 齋藤 哲治
    2004 年 28 巻 3 号 p. 322-325
    発行日: 2004年
    公開日: 2006/11/24
    ジャーナル オープンアクセス
    Microstructural studies revealed that a Co-Zr-B alloy ingot had coarse grains of Co23Zr6, Co5Zr, and Co3ZrB2 phases. Melt-spinning of the alloy ingot resulted in the formation of fine equiaxed grains. The resultant melt-spun ribbons consisted of the Co5Zr and Co23Zr6 phases and showed coercivities over 1 kOe. Heat treatment of Co-Zr-B melt-spun ribbons resulted in an increase in coercivity. The coercivity of annealed Co-Zr-B melt-spun ribbons was strongly dependent on the alloy composition. A high coercivity of 5 kOe was achieved in a composition of Co78Zr18B4 and Co80Zr18B2. The Co-Zr-B melt-spun ribbons exhibited a maximum energy product comparable to that of the hard ferrites.
  • 槇田 顕, 川久保 忠通, 中村 英滋, 杉山 英二, 青木 雅昭
    2004 年 28 巻 3 号 p. 326-329
    発行日: 2004年
    公開日: 2006/11/24
    ジャーナル オープンアクセス
    Demagnetization of Nd-Fe-B sintered magnets under proton and neutron irradiation near the beam line of a proton synchrotron was investigated. Magnets with coercivities of less than 1.3 MA/m showed obvious flux loss proportional to the absorbed dose. On the other hand, the flux loss was less than 1% after 4.1 kGy irradiation of magnets with coercivities greater than 2.0 MA/m. Since all of the magnets have the same Curie temperature, the difference in the demagnetization rate can be attributed to the probability of nucleation of a reverse domain in a locally heated region located around a knock-on atom, which is analogous to the thermal demagnetization of the magnets that usually starts below their Curie points.
  • 神木 太朗, 中川 茂樹
    2004 年 28 巻 3 号 p. 330-334
    発行日: 2004年
    公開日: 2006/11/24
    ジャーナル オープンアクセス
    The magnetic characteristics of FePt bilayers annealed in various atmospheres were investigated. The in-plane coercivity of FePt bilayers changed markedly in response to the annealing atmosphere. FePt bilayers annealed in hydrogen atmosphere exhibited coercivities of several kOe above 400°C. However, specimens annealed in nitrogen and argon atmosphere did not exhibit FePt ordered phase. X-ray photoelectron spectroscopy study clarified that the oxygen introduced with Fe formed Fe2O3 and made interdiffusion between the Fe and Pt layers difficult. Suppression of inter-diffusion caused degeneration of ordered FePt phase. Annealing in hydrogen atmosphere was found to be effective for removing the oxygen, and led to the formation of FePt ordered phase during the annealing. Moreover, specimens annealed in a high-pressure hydrogen atmosphere showed higher in-plane coercivity than specimens annealed under low pressure. High-pressure annealing also decreased the ordering temperature from 400°C to 350°C.
  • 野田 朋樹, 神島 謙二, 柿崎 浩一, 平塚 信之
    2004 年 28 巻 3 号 p. 335-338
    発行日: 2004年
    公開日: 2006/11/24
    ジャーナル オープンアクセス
    Pyrolysis of triethylamine in reduced pressure yielded carbon-based magnetic materials. A sample pyrolized at 1198 K for 30 min. showed ferromagnetic behavior at 300 K. The saturation magnetization of this sample was 0.53 emu/g at 300 K, and its Curie temperature was above 800 K. After annealing at 800 K in a magnetic field of 1 T, the magnetization of this sample increased from 0.49 to 0.62 emu/g at 1 T. In the ESR spectra, the sample’s spin density decreased after annealing in a magnetic field. These results suggest that annealing in a magnetic field causes rearrangement of the radical spin.
  • 関口 康爾, 清水 正義, 齊藤 英治, 宮島 英紀
    2004 年 28 巻 3 号 p. 339-342
    発行日: 2004年
    公開日: 2006/11/24
    ジャーナル オープンアクセス
    We have investigated the current-voltage characteristics of ferromagnetic Ni nanowires, using break-junction method. At liquid-helium temperature, nanowires were sustainable typically for a few minutes. The measured current-voltage curves for ferromagnetic Ni show a nonlinear property, which is in contrast to the case of diamagnetic Cu. This indicates that magnetic properties such as the local magnetic structure play an important role in the electronic transport of nanowires.
  • 山口 明啓, 谷川 博信, 小野 輝男, 那須 三郎, 三宅 耕作, 壬生 攻, 新庄 輝也
    2004 年 28 巻 3 号 p. 343-346
    発行日: 2004年
    公開日: 2006/11/24
    ジャーナル オープンアクセス
    We report direct observation of current-driven domain wall (DW) motion by using a well-defined single DW in a micro-fabricated magnetic wire. Magnetic force microscopy was used to visualize the current-driven DW motion. We measured the depinning field of the DW and the critical electric current density for the current-driven DW motion at several pinning sites.
  • 神原 陽一, 竹下 之典, 的場 正憲, 京免 徹, 伊藤 満
    2004 年 28 巻 3 号 p. 347-350
    発行日: 2004年
    公開日: 2006/11/24
    ジャーナル オープンアクセス
    We report the Mn doping effect in FeCr2S4, which does not possess heterovalency, or static Jahn-Teller distortion, but exhibits large magnetoresistance. In order to see the effects of substituting Fe2+ for Mn2+ on the conduction, magnetism, and magnetoresistance, we carried out an experimental study of the electrical and magnetic properties of Fe0.5Mn0.5Cr2S4. FeCr2S4 has a spin-glass phase below 60 K ( = Tg) and a ferrimagnetic phase in the temperature range 60-170 K (Tc = about 170 K). In Fe0.5Mn0.5Cr2S4, both the spin-glass and ferrimagnetic transitions are observed in lower temperature regions (Tg = 45 K, Tc = 140 K). FeCr2S4 is a semiconductor, but exhibits metallic-like behavior in the temperature range 150-170 K. Fe0.5Mn0.5Cr2S4 does not exhibit such metallic behavior, but anomalous transition of the temperature dependence of resistivity is observed in the temperature range 100-180 K. Fe0.5Mn0.5Cr2S4 exhibits a larger maximum negative magnetoresistance (MR) than FeCr2S4. Thses experimental data can be well explained on the basis of the polaron model.
  • 園田 大樹, 乾 成里, 大平 膺一, 古関 隆章
    2004 年 28 巻 3 号 p. 351-355
    発行日: 2004年
    公開日: 2006/11/24
    ジャーナル オープンアクセス
    We studied a magnetic levitation system for an X-Y linear synchronous motor (X-Y LSM) combining a four-pole yoke hybrid electromagnet with the X-Y LSM armature This system makes possible a noncontact two-dimensional drive. A four-pole yoke hybrid electromagnet can control three degrees of freedom by itself. In a steady state this system is suspended using only permanent magnet forces, and the control current converges to zero. In this paper, we describe an observer using only the gap length sensor. A gap length controller and zero power controller were designed based on the observer.
  • 神吉 輝夫, 田中 秀和, 川合 知二
    2004 年 28 巻 3 号 p. 356-359
    発行日: 2004年
    公開日: 2006/11/24
    ジャーナル オープンアクセス
    We fabricated ferromagnetic La0.8Ba0.2MnO3 thin films and systematically investigated the Curie temperature (Tc) for film thickness dependence. Tc was defined as a maximum peak of a dM/dT. We found that the Tc gradually increased with decreasing film thickness from Tc of the bulk (270 K). The 20-nm-thick film showed a maximum peak of Tc (= 310 K) against the thickness and a Tc decreased blow 20-nm-thick film. However, even the ultra thin film with 5 nm thickness had a Tc of 290 K, near room temperature. In order to apply this result to an application working at room temperature, we constructed field-effect transistor structures using the ferromagnetic (La,Ba)MnO3 ultra thin film with the aim of controlling the metal-insulator transition at room temperature by applying an electric field. Investigations revealed that the transition temperature changed from 237.0 K to 242.0 K for the La0.90Ba0.10MnO3 channel layer by ferroelectric remnant polarity (±50 μC/cm2) and from 280.5 K to 283.0 K (±26 μC/cm2) for the La0.85Ba0.15MnO3 channel layer. These shifts, which were linearly proportional to the magnitude of ferroelectric remnant polarization, are induced by the accumulative charge due to the electric field.
  • 佐藤 哲也, 角田 匡清, 張 其武, ジャヤデワン バラチャンドラン, 高橋 研
    2004 年 28 巻 3 号 p. 360-363
    発行日: 2004年
    公開日: 2006/11/24
    ジャーナル オープンアクセス
    The powder magnetoresistance (PMR) effect of cold-pressed (Cr-M)O2 mechanical-alloyed-powder was investigated. As additives, M, vanadium and iron were selected. The PMR ratio measured at 77 K increases from 2% to 6% with increasing iron content up to 5%, while the PMR ratio of (Cr-V)O2 powder monotonically decreases with increasing vanadium content. Through measurement at 4.2 K, it was concluded that the changes in the PMR ratio are not due to changes in the Curie temperature of (Cr-M)O2. The PMR effect of cold-pressed CrO2 powder is stable up to 360°C.
  • 武井 重人, 上水 孝徳, 森迫 昭光, 松本 光功
    2004 年 28 巻 3 号 p. 364-367
    発行日: 2004年
    公開日: 2006/11/24
    ジャーナル オープンアクセス
    In order to prepare Sm-Co films with perpendicular magnetic anisotropy, effects of the substrate temperatures during the preparations of both the Cu underlayer and the Sm-Co layer were studied. The Cu underlayer was varied from (111) preferred- oriented structure to (200) structure due to the substrate temperature. When the Sm-Co layer was prepared at 300°C onto the Cu underlayer with (111) preferred-oriented structure, the X-ray diffraction line from SmCo5 (002) plane was observed and the magnetic easy axis was in the perpendicular direction. The coercivity in the perpendicular direction was about 9.6 kOe and the coercivity in the in-plane direction was about 1.4 kOe.
  • 今北 健一, 角田 匡清, 高橋 研
    2004 年 28 巻 3 号 p. 368-371
    発行日: 2004年
    公開日: 2006/11/24
    ジャーナル オープンアクセス
    The effect of thermal annealing under ultra-high vacuum on the metallurgical microstructure of (111) -textured face-centered cubic (FCC) metal thin films was investigated. The surface morphology of 500-Å-thick metal films drastically changes with increasing annealing temperature. Regardless of the kind of metal, the morphological changes can be classified into four stages, when the annealing temperature, TIR, is normalized by the respective melting point of the metals, TM. In stage I , 0.15 ≤ TIR/TM < 0.3, the surface roughness, Ra, of metal films decreases to ∼ 3 Å. In stage II, 0.3 ≤ TIR/TM ≤ 0.35, remarkable grain growth occurs, and the lateral grain diameter exceeds 1000 Å. Small (∼ 200 Å) crystals appear on the large grains in the stage II’, 0.35 < TIR/TM ≤ 0.45, and they grow large and coarsen the Ra in stage III, 0.45 < TIR/TM. We conclude that ultra-high vacuum annealing in stage II is effective in realizing large lateral grain size with small surface roughness in FCC metal films.
  • 児玉 宏喜, 百瀬 悟, 渦巻 拓也, 田中 厚志
    2004 年 28 巻 3 号 p. 372-375
    発行日: 2004年
    公開日: 2006/11/24
    ジャーナル オープンアクセス
    We have investigated magnetic properties and crystal structures of chemically synthesized FePt nanoparticle media. The average grain diameter estimated as 4.4 nm and σ/D 13 % from TEM bservation. We found that each anoparticle is not coalesced after annealing for 750°C-30 min. We were confirmed L10 structure of FePt nanoparticles form the electron diffraction patterns. Diffraction rings for (001) and (110) are confirmed clearly. Hk and Ku V values were estimated from the temperature dependence of Hc. Ku V/kT value was 41 at room temperature.
  • 藤 慶彦, 宮崎 孝道, 岡本 聡, 北上 修, 島田 寛, 小池 淳一
    2004 年 28 巻 3 号 p. 376-379
    発行日: 2004年
    公開日: 2006/11/24
    ジャーナル オープンアクセス
    We studied the c-axis direction and ordering process of L10-FePt thin films during thermal annealing. For the thinner (5 and 10 nm) samples, rapid annealing clearly promoted (001) orientation with higher L10 ordering. However, for the thicker (50 nm) samples, (111) orientation was dominant independent of the annealing conditions. We suggest that stress direction and its relaxation during thermal annealing strongly relate to these remarkable changes of orientation and L10-ordering.
  • 岩坪 聡
    2004 年 28 巻 3 号 p. 380-383
    発行日: 2004年
    公開日: 2006/11/24
    ジャーナル オープンアクセス
    Three kinds of Fe films, without Ar bombardment [BNON], with Ar bombardment after deposition [BAFT], and with Ar bombardment during deposition [BDUR], were prepared by dual ion-beam sputtering. The relationship between the morphology and the magnetic characteristics of the Fe films was investigated as a function of the film thickness tF in the wide range between 0.5 and 600 nm. The sputtering voltage and current were fixed at 1200 V and 50 mA, respectively. The Ar bombardments for BAFT and BDUR were carried out at an ion acceleration voltage of 200 V. The features of the film growth were very different according to the type of bombardment. The BNON films changed from an island structure to a layer structure at tF between 8.0 and 16 nm. The BAFT and BDUR films were revealed smoother surfaces than BNON and echibited a layer structure at tF above 1.0 nm. However, the saturation magnetization 4πMS of BDUR abruptly decreased at tF below 8.0 nm, since the Ar bombardment knocked Fe atoms into the surface region of the glass substrate during the initial growth stage. On the other hand, 4πMS of BNON and BAFT took an almost constant value of 21.5 kG with a fluctuation of about 5%. The coercivity Hc of BAFT had lowest value all the films at tF below 4.0 nm. These results indicate that Ar bombardment after deposition is useful for preparing ultrathin Fe films with excellent soft magnetic properties.
  • 竹澤 昌晃, 森 智礼, 山崎 二郎
    2004 年 28 巻 3 号 p. 384-387
    発行日: 2004年
    公開日: 2006/11/24
    ジャーナル オープンアクセス
    Micron-scale rectangular and round-edged Ni80Fe20 ferromagnetic dots were studied by Kerr microscopy. Samples of ferromagnetic dots were prepared by means of electron-beam lithography and RF sputtering. The magnetization reversal process in rectangular dots with a large aspect ratio included rapid magnetization switching, which is convenient for memory and sensor applications. Moreover, the residual magnetization of round-edged dots was larger than that of rectangular dots, because the nucleation of reversal domains around the edges of dots can be eliminated by the shape effect. It is concluded that the most preferable magnetization reversal process for memory applications was obtained by using round-edged dots.
  • 尾藤 輝夫, 牧野 彰宏, 井上 明久, 増本 健
    2004 年 28 巻 3 号 p. 388-392
    発行日: 2004年
    公開日: 2006/11/24
    ジャーナル オープンアクセス
    The effects of the structural inhomogeneity, volume fraction (va), and Curie temperature (Tcam) of an inter-granular amorphous phase on the soft magnetic properties of nanocrystalline Fe-Nb-B(-P-Cu) alloys were investigated. The Fe85Nb6B9 alloy has a mixed as-quenched structure composed of an amorphous phase and α-Fe grains, and an inhomogeneous nanostructure including coarse α-Fe grains with a diameter of about 40 nm after crystallization. The simultaneous replacement of B by 1 at% P and Fe by 0.1 at% Cu in the alloy decreases the α-Fe grain size to the nano-scale in an as-quenched state and leads to a homogeneous nanostructure, small va, and high Tcam after crystallization. Analysis based on the random anisotropy model shows that a homogeneous nanostructure with small va and high Tcam provides good soft magnetic properties.
  • 三島 史人, 山崎 貞郎, 吉田 和悦, 中根 央, 武田 真一, 泉 佳伸, 西嶋 茂宏
    2004 年 28 巻 3 号 p. 393-396
    発行日: 2004年
    公開日: 2006/11/24
    ジャーナル オープンアクセス
    Feasibility study of magnetic separation of sample powders with small difference in their specific gravity, which was ineffective, was carried out by magnetic separation by focusing on the difference in their magnetic properties. An apparatus to separate the ferromagnetic particles from the mixed powder with small difference in its specific gravity was made. To investigate the relation between the sizes of the particles and separation efficiency, systematical examination of the separation ratio was done while changing the sizes of the ferromagnetic and paramagnetic particles. Successful separation of dry powders with small difference in their gravities was achieved in a magnetic field by using this apparatus. With a sample composed of a mixture of Cu-Zn ferrite and Al2O3 with the grain size of 45 μm, the separation efficiency of the Al2O3 was close to 100%. As the size of particles of the mixed powers became smaller, its separation efficiency decreased, which could be attributed to the aggregation/flocculation of each particle.
  • 林 直人, 宮本 泰敬, 町田 賢司, 玉城 孝彦
    2004 年 28 巻 3 号 p. 397-400
    発行日: 2004年
    公開日: 2006/11/24
    ジャーナル オープンアクセス
    A remarkable reduction in coercivity Hc was found in sputtered (Fe70Co30)99(Al2O3)1 films on Ni-Fe and Cu underlayers. A decrease in Hc from 80 to 4∼6 Oe was observed for Ni-Fe and Cu underlayers as thin as 2 nm, but the decrease was less for Ta. No significant difference in soft magnetic properties was observed with the thickness of a Ni-Fe layer in the range 0.5∼10 nm, that with of a Cu layer in the range 0.2∼10 nm, or with that of an Fe-Co-Al-O layer in the range 50∼480 nm. The optimized film has a saturation magnetization of 23.5 kG; the real part of the permeability shows frequencies up to 1.3 GHz of 1200∼2520, and the imaginary permeability peaks at beyond 2 GHz, corresponding to the ferromagnetic resonance frequency. All underlayers induced a bcc-(110) preferred grain orientation in Fe-Co, and this orientation was strongest with Ta. Transmission electron microscopy of cross-sections showed that clear columnar grains were visible with all underlayers, with an average grain size of around 50 nm with Ta, dropping to 7-10 nm for Ni-Fe and Cu. This allows us to explain qualitatively the reduction in Hc using Hoffmann’s ripple theory.
  • 伊藤 哲夫, 吉田 栄吉, 岡本 聡, 北上 修, 島田 寛
    2004 年 28 巻 3 号 p. 401-404
    発行日: 2004年
    公開日: 2006/11/24
    ジャーナル オープンアクセス
    It has been verified that high permeability granular films work as RF electromagnetic noise absorbers when they are placed in the vicinity of electronic devices radiating RF noise. However their limited resistivity induces eddy current that re-radiates RF noise back to the source. In this paper it is reported that thin films produced by co-evaporation of Ni80Fe20 and B2O3 have a very thin columnar structure that leads to a very high resistivity. The nano-structure is an assembly of thin columns that have a perpendicular anisotropy with the hard axis in the in-plane direction. The films exhibit a remarkable feature as RF noise absorbers that are equivalent to the conventional noise absorbing sheets that are 50 times thicker than the films.
  • 福田 祐三, チョムスワン コムクリット, 山田 外史, 岩原 正吉, 脇若 弘之, 庄司 茂
    2004 年 28 巻 3 号 p. 405-408
    発行日: 2004年
    公開日: 2006/11/24
    ジャーナル オープンアクセス
    The eddy-current testing technique is an interesting method for detecting defects on bare printed circuit boards. This technique detects various defects without mechanical stress to PCB patterns. Usually various pickup coils are used in an ECT probe as a magnetic sensor. Pickup coil sensors, however, do not show enough S/N ratio to detect defects in high-density PCBs, whose conductors are less than 100μm. We propose a new ECT probe with a spin-valve giant magnetoresistive (SV-GMR) sensor for inspection of PCBs. SV-GMR sensors show high sensitivity to a small magnetic field in one direction. This sensor senses a magnetic field as varying its resistance unlike inductive sensors such as a pickup coil.
    In this paper, we investigated the sensing properties of a SV-GMR sensor with changing axes, frequencies, and magnetic field amplitudes, and discussed problems that could occur in replacing a pickup coil with SV-GMR.
  • 鎌田 康寛, 中野 朋和, 高橋 正氣, 荒 克之, 菊池 弘昭, 越後谷 淳一, 八重樫 光
    2004 年 28 巻 3 号 p. 409-412
    発行日: 2004年
    公開日: 2006/11/24
    ジャーナル オープンアクセス
    A Charpy impact test and magnetic hysteresis measurement were performed on Fe-0.15wt%C steels with different cold-rolling ratios. As the cold-rolling ratio was increased, the ductile-brittle transition temperature (DBTT) and coercive field increased simultaneously. This correlation originated from an increase in the dislocation density induced by plastic deformation. This study shows the possibility of applying magnetic methods to pressure vessel surveillance at nuclear power plants.
  • 森 啓士郎, 渡邊 浩二, 柳瀬 俊次, 岡崎 靖雄, 枦 修一郎
    2004 年 28 巻 3 号 p. 413-416
    発行日: 2004年
    公開日: 2006/11/24
    ジャーナル オープンアクセス
    We examined a method for measuring the magnetic properties of ring-shaped electrical steel sheets. The magnetic properties measured in ring-shaped samples depend on the orientation of stacked sheets, in spite of non-oriented sheet samples. We also measured the two-dimensional magnetic properties of non-oriented samples. Magnetic properties that are dependent on the stacking orientation appear to differ due to magnetic flux passing between the sheets.
  • 才田 大輔, 高橋 琢二
    2004 年 28 巻 3 号 p. 417-420
    発行日: 2004年
    公開日: 2006/11/24
    ジャーナル オープンアクセス
    For a purpose of measuring local transport properties in fine structures, a novel current detection method through magnetic force microscopy was proposed and demonstrated. Around an 8μm wide GaAs/AlGaAs mesa stripe, the magnetic fields induced by AC currents were observed by MFM simultaneously with topographies. Since a direction of the magnetic field gradients is perpendicular to the mesa stripe, the obtained magnetic field images strongly depended on the measuring configurations, in which the cantilever beam and the mesa stripe were in parallel or in perpendicular. As we expected, the amplitude was under the noise level in the perpendicular configurations, while we clearly observed the enhancement of amplitude and the phase inversion at the both sides of the mesa stripe in the parallel configuration. These results agreed very well with the numerical simulation which showed the existence of the large magnetic field gradients at the both sides of the mesa stripe. Linear relationship between the peak amplitude values and the AC current was also confirmed.
  • 竹内 輝明, 柴崎 利成, 深尾 隆三, 若林 康一郎
    2004 年 28 巻 3 号 p. 421-424
    発行日: 2004年
    公開日: 2006/11/24
    ジャーナル オープンアクセス
    We formed optical switches in which a mirror is driven by a magnetostrictive cantilever, and measured their properties. The cantilever has a cross-sectional structure of Al (10 nm)/SmFe (6μm)/Al (10 nm)/Cr (1.2μm)/glass (20μm) and the dimensions are 12 mm ×0.8 mm. A cantilever with a gold mirror on the surface is installed in the gap of a magnetic circuit. The gap field is 1.5 kOe for an electric current of 200 mA. At this current the deflection of a cantilever is 230μm. These components are combined with optical fibers with a lens and a 1 × 2 optical switch is formed. The insertion loss and the crosstalk are 0.23 dB and −64.4 dB, respectively. The power consumption is 120 mW, which is expected to be decreased by improving the magnetostrictve properties. The switching time is 15 ms, which is determined by a vibration of the cantilever. Damping techniques for the vibration can reduce the switching time.
  • 早川 秀一, 中村 健二, 赤塚 重昭, 葵木 智之, 川上 峰夫, 大日向 敬, 皆澤 和男, 一ノ倉 理
    2004 年 28 巻 3 号 p. 425-428
    発行日: 2004年
    公開日: 2006/11/24
    ジャーナル オープンアクセス
    Since an EIE-core variable inductor is constructed from cores and windings, it has good features for an electric power apparatus, such as simple construction and high reliability. The variable inductor does not need any gaps for harmonic current reduction and has a suitable structure for a larger capacity. For optimum design, a quantitative analysis method for the variable inductor is important. In a previous paper, we derived a two-dimensional nonlinear magnetic circuit model of the EIE-core and found operating characteristics of the variable inductor. Although the calculation value and actual measurement showed good coincidence, in the large domain of the control current, a tendency was shown to expand quantitive error, and further improvement in calculation accuracy became a subject. In this paper, we present a three-dimensional magnetic circuit to improve analysis accuracy, and compared calculated results with actual measurements.
  • 鶴本 勝夫, 熊坂 諭恭
    2004 年 28 巻 3 号 p. 429-432
    発行日: 2004年
    公開日: 2006/11/24
    ジャーナル オープンアクセス
    We studied a magnetic gear which is noiseless, oilless, and maintenance-fee, intend for use in a wind-power generator. Generally, industrial machines such as cams need not only a constant speed, but also a variable speed ratio and displacement. Cams can be replaced by eccentric gear or non-circular gear. In the latter case, it is reasonable to use a magnetic gear, because it has a flexible center distance and can be expected to act as a shock absorber in meshing.
    In this report, the operation principle of non-circular magnetic gear is explained and a method of designing such gears for practical use is discussed. The operation principle is demonstrated by reference to a trial model and the results of a static test of performance characteristics are examined.
  • 干葉 淳, 仙道 雅彦, 石山 和志, 須田 祐司, 荒井 賢一, 小丸 達也, 白土 邦男
    2004 年 28 巻 3 号 p. 433-436
    発行日: 2004年
    公開日: 2006/11/24
    ジャーナル オープンアクセス
    A magnetic actuator for colon endoscope navigation was fabricated. We conducted motion tests of the actuator in the small intestine of a pig and the large intestine of a living dog. The actuator is composed of a permanent magnet and a spiral structure, and is attached to the pointed end of an imitation endoscope. When a rotational magnetic field is applied, the actuator rotates and moves in the intestine. It was able to draw the imitation endoscope forward without injuring and changing the shape of the intestine. This result shows that the actuator has the potential to be use for colon endoscope navigation.
  • 柿川 真紀子, 細野 隆次, 橋本 松進, 岩原 正吉, 山田 外史
    2004 年 28 巻 3 号 p. 437-440
    発行日: 2004年
    公開日: 2006/11/24
    ジャーナル オープンアクセス
    In this study, we investigated whether extremely low frequency magnetic fields (ELFMF) induce DNA damage or physiological abnormality in the bacterial cell using bacteriophage λ. By exposure to magnetic fields for about 8 hours, the bacteriophages shifted to lytic growth 2 times as often as control. The mitomycin C, mutagenic reagent, was shifted the bacteriophages from lysogenic to lytic growth 46-times as often as control. These results suggested that ELF magnetic field (60 Hz, 45 mT) did not induce DNA damage in the bacterial cell as mitomycin C. But ELF magnetic field (60 Hz, 45 mT) might induce physiological damage in the bacterial cells.
  • 相馬 宗尚, 仙道 雅彦, 石山 和志, 荒井 賢一
    2004 年 28 巻 3 号 p. 441-444
    発行日: 2004年
    公開日: 2006/11/24
    ジャーナル オープンアクセス
    A magnetic micromachine capable of moving in a liver was fabricated. It consisted of a stainless steel tip, a permanent magnet, and a spiral shape made with a tungsten wire. The magnet was magnetized in the direction of its diameter. The diameter of the machine was 0.9 mm, small enough for it to be inserted by means of a medical injector. When a rotational magnetic field was applied, the machine rotated and moved in a liver. According to our experimental results, the strongest force could be exerted by using two spirals, each with an angle of 60°. The micromachine was able to move a distance of 40 mm in a pig’s liver. It thus has great potential for medical applications.
  • 鹿野 元樹, 野元 崇, 佐藤 文博, 松木 英敏, 佐藤 忠邦
    2004 年 28 巻 3 号 p. 445-448
    発行日: 2004年
    公開日: 2006/11/24
    ジャーナル オープンアクセス
    The motor function lost by traffic accidents etc. can be rebuilt or assisted by applying appropriate electric stimulation from the outside. This treatment method is called “Functional Electrical Stimulation (FES).” We plan to create a completely implantable FES system for the next generation of FESs. This is a contactless power and signal transmission method using electromagnetic coupling between a primary coil located outside the body and a secondary coil implanted inside. In this research, we designed an implantable stimulator which could receive both power and signal at the same time. This stimulator has a microminiature shape of about 10 mm in length and consists of two types of coils, one for power receiving and the other for signal receiving. The signal receiving coil has a structure which can reduce the influence of the magnetic field on the power supply without using a filter. This time, we examined the shape of a stimulator that can receive higher power and higher signal voltage experimentally.
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