Transactions of the Magnetics Society of Japan
Online ISSN : 1884-6726
Print ISSN : 1346-7948
ISSN-L : 1346-7948
Volume 2 , Issue 2
Showing 1-19 articles out of 19 articles from the selected issue
  • Masanori Fukushima, Kaneo Mohri, Takuji Kataoka, Mippo Matsumoto
    2002 Volume 2 Issue 2 Pages 15-18
    Published: May 01, 2002
    Released: August 25, 2010
    JOURNAL FREE ACCESS
    We examined the effects of milli Gauss pursed magnetic field on phosphate buffeted saline solution (PBS) and pure water. Milli Gauss pursed magnetic field was generated by a Helmholz coil using a functional generator. A pursed magnetic field was applied on PBS in glass bottle 12 hrs prior to the assay of neutrophil phagocytic activity or the measurement of intracellular Ca2+ level. PBS exposed to the pursed magnetic field was found to markedly enhance the phagocytic activity of neutrophils. The intracellular Ca2+ level of neutrophils elevated immediately after exposure to the magnetized PBS. Here we show that milli Gauss level pursed magnetic field applied tonic water solution such as PBS alter its physico-chemical properties and the magnetized PBS exerts extraordinary biological effects.
    Download PDF (5173K)
  • Sarbanoo Das, Shigeki Nakagawa
    2002 Volume 2 Issue 2 Pages 19-22
    Published: May 01, 2002
    Released: August 25, 2010
    JOURNAL FREE ACCESS
    Magnetic interaction as well as magnetization process in the Co-Cr-Ta media and Co/Pt multilayered media under the canted magnetic field have been investigated by using the Anomalous Hall effect measurement. ΔM plot has been calculated from the initial curve and the hysteresis curve of the samples to evaluate the interaction among the magnetic particles. Magnetic field was applied in the direction from the normal to in-plane direction. Co-Cr-Ta thin film exhibited the magnetic interaction depending on field direction while the magnetic interaction in the Co/Pt multilayered thin film remained unchanged though the magnetic field direction was changed.
    Download PDF (820K)
  • Hiroyasu Kawano, Takeshi Morikawa, Koji Matsumoto, Keiji Shone
    2002 Volume 2 Issue 2 Pages 23-27
    Published: May 01, 2002
    Released: August 25, 2010
    JOURNAL FREE ACCESS
    The relationships among magnetic properties, film structures, and noise characteristics of FeC films were examined with particular emphasis on soft magnetic backlayers of double-layered perpendicular magneti recording media. FeC films were fabricated on glass disks using DC magnetron sputtering by a conventional cosputtering method with Fe and C targets. The films were deposited at room temperature without application of magnetic fields. No heat processes were applied after deposition. The Fe and C contents in the films were varied by individually controlling the electrical power for the Fe and C targets. Nana-scale downsizing for both the film structures and the magnetic domains and the formation of radial magnetic anisotropy in an as-deposited state produce soft magnetic FeC films with both low media noise and high saturation magnetization of around 19 kGauss. A coercive force in the magnetic easy axis of less than 1 Oe reduces media noise in the FeC film. An anisotropy field of over 20 Oe suppresses spike noise in the FeC film. A high electrical resistivity of about 120 μΩcm and a high permeability of around 900 that remains constant up to 1 GHz in FeC films suggest future applications for high density recording media.
    Download PDF (1329K)
  • Mitsunori Mochida, Takao Suzuki
    2002 Volume 2 Issue 2 Pages 28-31
    Published: May 01, 2002
    Released: August 25, 2010
    JOURNAL FREE ACCESS
    Thermal stability of TM-rich Tbx (Fe90Co10) 100-x (x=13.5, 17.2) disks (KuV/kBT) is estimated by a reverse DC-erase noise method and the Sharrock's equation. The method involves a spinstand for hard disks, and hard disk glass substrates with TbFeCo deposited as a magnetic layer of perpendicular anisotropy were used. As the result, the high stability was shown for a high coercivity disk. This indicates that the pinning effect, which is related to coercivity, is one of the important factors for thermal stability.
    Download PDF (556K)
  • F. Yamashita, K. Takasugi, H. Yamamoto, H. Fukunaga
    2002 Volume 2 Issue 2 Pages 32-35
    Published: May 01, 2002
    Released: August 25, 2010
    JOURNAL FREE ACCESS
    The miniaturization of electric motors such as small stepping motors has progressed rapidly, and has been accompanied by a drastic decrease in the mechanical output of the motors relative to the reduction in size. One of the causes of this decrease is insufficient magnetization in the magnets used in motors because of a decrease in the pole-pitch. Since so-called nanocomposite flakes are easily magnetized in comparison with conventional Nd2Fe14B melt-spun flakes, we used bonded-magnet rotors prepared from α-Fe/R2Fe14B nanocomposite melt-spun flakes with high remanence in small stepping motors, and studied the effects of the coercivity and remanence of the flakes on the magnetic stability of the magnets and the characteristics of the motors. As a result, when the nanocomposite flakes had a coercivity of 600-700 kA/m and a remancence higher than 950 mT, the motors exhibited adequate magnetic stability atoperating temperature as well as a higher mechanical output than that obtained using a conventional Nd2Fe14B bonded magnet.
    Download PDF (881K)
  • H. Mamiya, I. Nakatani, T. Furubayashi, M. Ohnuma
    2002 Volume 2 Issue 2 Pages 36-48
    Published: May 01, 2002
    Released: August 25, 2010
    JOURNAL FREE ACCESS
    Approaches suitable for analyses of superparamagnetism are studied for a well-isolated ferromagnetic nanoparticle assembly. In order to reduce the effects of the particle size distribution, we prepared iron-nitride particles with a narrow size distribution. In the case of static behavior, it is clarified that the conventional approach based on the Langevin function gives spurious information on the distribution of magnetic moments below the temperature that is several times as high as its blocking temperature. The valid approach for analyzing the magnetization curves requires taking into account the anisotropy of each particle in the temperature range. In the case of dynamic behavior, the conventional approach has used the temperature Tmax at which the susceptibility shows a maximum when the temperature is scanned. If the relaxation time in finite fields is estimated using Tmax, we obtain the spurious result that the relaxation slows down with the applied field. The numerical calculations show that this spurious result is affected by the variation of static behavior. Hence, this study proposes an original approach whose results are independent of such effects. The obtained relaxation time in finite fields is quantitatively consistent with the predictions of a classical theory of superparamagnetism.
    Download PDF (2749K)
  • Takashi Kimura, Yoshio Itagaki, Fujio Wakaya, Kenji Gamo
    2002 Volume 2 Issue 2 Pages 49-52
    Published: May 01, 2002
    Released: August 25, 2010
    JOURNAL FREE ACCESS
    The influences of the stray field from one ferromagnetic layer on the other ferromagnetic layer in 500-nm-wide magnetic wires consisting of NiFe/Cu/NiFe/CoO spin-valve structures, in which the easy axis of the pinned layer could be aligned to any desired direction, were investigated. It is shown that the stray field can be negligible by using the pointed end with the condition that the exchange anisotropy is parallel to the wire axis. A quantitative analysis of the stray field was also discussed.
    Download PDF (891K)
  • Shiori Kaji, Gendo Oomi, Fuminori Honda, Seiji Mitani, Koki Takanashi
    2002 Volume 2 Issue 2 Pages 53-55
    Published: May 01, 2002
    Released: August 25, 2010
    JOURNAL FREE ACCESS
    We have studied electrical resistivity of Co43Al24O33 insulating granular films under high pressure. This material consists of nanometer-sized Co granules embedded in an Al-oxide matrix. in which electron tunneling between Co granules and electrical charging effect (Coulomb blockade) of Co granules plays an important role for the electrical conduction. The tunneling conductivity is enhanced by applying pressure. and the enhancement is more significant at low temperatures. The characteristic temperature dependence represented by logρ∝T-1/2 is observed at high pressure up to 3.1 GPa. The proportional coefficient of logρ∝T-1/2 relationship shows a clear tendency to decrease with increasing pressure. This behavior can be mainly interpreted by the suppression of charging effect. assuming that the Al-oxide matrix is more compressible than Co granules.
    Download PDF (535K)
  • Toshikazu Tanaka
    2002 Volume 2 Issue 2 Pages 56-58
    Published: May 01, 2002
    Released: August 25, 2010
    JOURNAL FREE ACCESS
    Crystallographic and magnetic properties caused by nonequilibrium in sputter deposited Mn ferrite thin films and their relaxation by heat treatment are examined. A compressive stress is present in as-deposited films, although they are crystalline and have a spinet structure. The magnetization of the as-deposited films does not saturate even at 15 kOe. Compared with the bulk sample, the as-deposited films have high field susceptibility and high Curie temperatures. Heat treatment in an N2 atmosphere at 800°C relaxes these properties. These properties in the as-deposited films are considered to be attributed to vacancies, dislocations, voids, and a nonequilibrium ion configuration produced at deposition.
    Download PDF (546K)
  • Takashi Hamaya, Junji Oikawa, Masaaki Doi, Hidefumi Asano
    2002 Volume 2 Issue 2 Pages 59-62
    Published: May 01, 2002
    Released: August 25, 2010
    JOURNAL FREE ACCESS
    The magnetic properties of Fe-C thin film prepared by the ion-beam sputtering method (IBS) using a composite target were investigated. A single-phase Fe3C thin film was obtained from as-deposited amorphous Fe-C thin films after heated up to 400°C. From magnetization measurement and X-ray diffraction, it was confirmed that the Fe3C film is single-phase without any impurity phase. Hyperfine parameters were estimated from the results of conversion electron Mössbauer spectroscopy (CEMS) measurement. The central values of the hyperfine field (Bhf = 205 kOe), isomer shift (IS = 0.20 mm/s), and quadrupole shift (QS = 0.03 mm/s) for the film are consistent with those for bulk Fe3C.
    Download PDF (695K)
  • Makoto Sawamura, Hirotaka Hosoi, Michiya Kimura, Guido Eilers, Agus Su ...
    2002 Volume 2 Issue 2 Pages 63-68
    Published: May 01, 2002
    Released: August 25, 2010
    JOURNAL FREE ACCESS
    The geometries and spin electronic states of single atomic strands consisting of Fe atoms were studied in comparison with similar strands of Au, Pt, Cu, Na, Mg, Al, Si, and Xe atoms, using first principles molecular orbital methods. Finite cluster models comprising six atoms were constructed. The optimized geometry of the wire was obtained for each element as the wire was elongated. Abnormally long atomic distances were observed in the cases of Fe, Au, Pt, Cu, Na, Mg, and Xe wires, which have shallow and broad s-orbitals in their valence shells. On the other hand, the wires formed from Al and of Siatoms collapsed while growing to lengths in excess of the bulk atomic distances. These atoms have σ-bonds with their neighboring atoms in the wires. Their electronic states create steep and deep potential energy wells, which prohibit long atomic distances.
    Download PDF (6658K)
  • Yasuhiro Kamada, Akihiro Itoh, Daisuke Takama, Masahiko Yamamoto
    2002 Volume 2 Issue 2 Pages 69-75
    Published: May 01, 2002
    Released: August 25, 2010
    JOURNAL FREE ACCESS
    The effects of hydrogenation on the structure, transport, and magnetic properties of TM/RE (TM = Fe, Co; RE = La, Y, Gd) multilayers were investigated. The following effects were found to be common to all TM/RE multilayers: (a) transition of RE layers from metal to semiconductor, (b) expansion of RE layers, and (c) enhancement of saturation magnetization. The hydrogenation technique is practicable for changing the interface state and producing a semiconductor layer inside the multilayer, and thus shows potential for producing new functional magnetic multilayers.
    Download PDF (1317K)
  • Gyorgy Safran, Saori Watanabe, Toshio Suzuki, Jun Ariake, Naoki Honda, ...
    2002 Volume 2 Issue 2 Pages 76-81
    Published: May 01, 2002
    Released: August 25, 2010
    JOURNAL FREE ACCESS
    The effects of Ti, Pt and Ti/Pt stacked intermediate layers were studied on the microstructure of Co-Cr-Nb-Pt double layer perpendicular magnetic recording media by transmission electron microscopy (TEM). The media without intermediate layer exhibited hcp (0001) texture formed by heteroepitaxy on the 20-40nm diameter fcc (111) columns of the permalloy back layer. The applied Ti intermediate layer was amorphised due to a chemical reaction with the permalloy. The subsequent Co-Cr-Nb-Pt layer was grown by new nucleation. It exhibited reduced grain size to 10-13nm, an initial growth layer and no remarkable preferred orientation. Pt intermediate layer provided (0001) texture of Co-Cr-Nb-Pt and 20-40nm grain size by heteroepitaxial growth. TEM study revealed high stress field at the permalloy/Pt/Co-Cr-Nb-Pt interfaces. In case of Ti/Pt stacked intermediate layer the Ti (5nm) interrupted heteroepitaxy. It provided high nucleation density and reduced grain size of the Pt (10nm) intermediate layer of preferred (111) orientation. These conditions favoured (0001) orientation and 10-16nm grain size of the heteroepitaxially grown Co-Cr-Nb-Pt recording layer. The increased coercivity of the Co-Cr-Nb-Pt layer on the Pt intermediate is attributed to stress induced anisotropy.
    Download PDF (3252K)
  • J. Olszewski, H. Fukunaga, Y. Yamashiro, J. Zbroszczyk, M. Hasiak, W. ...
    2002 Volume 2 Issue 2 Pages 82-85
    Published: May 01, 2002
    Released: August 25, 2010
    JOURNAL FREE ACCESS
    The phase composition, magnetic susceptibility and its disaccommodation of the amorphous and nanocrystalline Fe85. 4-xCoxZr5. 8Nb1B6. 8Cu1 (x = 0 or 42. 7) alloys were studied. We have found that in the nanocrystalline Fe42. 7Co42. 7Zr5. 8Nb1B6. 8Cu1 alloy the ordered α-FeCo phase is present. Moreover, that alloy exhibits the higher susceptibility at elevated temperatures than the Fe85. 4-xCoxZr5. 8Nb1B6. 8Cu1 one. The disaccommodation phenomenon in both investigated alloys is connected with relaxation processes occurring in the amorphous matrix.
    Download PDF (642K)
  • J. Zbroszczyk, Y. Yamashiro, J. Olszewski, H. Fukunaga, M. Hasiak, W. ...
    2002 Volume 2 Issue 2 Pages 86-89
    Published: May 01, 2002
    Released: August 25, 2010
    JOURNAL FREE ACCESS
    The microstructure, saturation magnetization, magnetic susceptibility and coercivity of the amorphous and nanocrystalline Fe83-xCoxNb3B13Cu1 (x=0 or 41.5) alloys were investigated. It was stated that the replacement of 41.5% of Fe atoms by Co atoms in the Fe83Nb3B13Cu1 alloy enhances the saturation magnetization. Moreover, the presence of α-FeCo phase and amorphous matrix with the high Curie temperatures in the nanocrystalline Fe41.5Co41.5Nb3B13Cu1 alloy improves high temperature magnetic properties. From Mou82ssbauer spectroscopy investigations we have found that α-FeCo phase in that alloy is atomically ordered.
    Download PDF (932K)
  • M Ohashi, G Oomi, S Koiwai, Y Uwatoko
    2002 Volume 2 Issue 2 Pages 90-92
    Published: May 01, 2002
    Released: August 25, 2010
    JOURNAL FREE ACCESS
    The magnetoresistance (MR) of single crystalline CeRh2Si2 has been measured at high pressure up to 2.3 GPa and at 4.2 K. At ambient pressure, the large MR has been observed. It is found that in a magnetic field dependence of MR, it shows a crossover near the critical pressure PC2=0.6 GPa, from H to a H2 dependence. The magnitude of MR, ΔR (P, H= 9 T) /R (P), shows a sudden decrease near PC2, where the magnetic structure changes. These results are discussed on the basis of pressure induced quantum phase transition.
    Download PDF (515K)
  • L.K.E.B Serrona, A Sugimura, R Fujisaki, T Okuda, N Adachi, H Ohsato, ...
    2002 Volume 2 Issue 2 Pages 93-97
    Published: May 01, 2002
    Released: August 25, 2010
    JOURNAL FREE ACCESS
    NdFeB thin films possessing high coercivity and perpendicular anisotropy were prepared with high reproducibility by means of RF sputtering deposition on Mo substrates with subsequent annealing treatment. The use of glass thermal insulation between the substrates and substrate holder during deposition made it possible to produce films with improved magnetic properties. The development of the magnetic properties were then found to have some dependence on the thickness of glass insulation making such films a realization of thin film permanent magnets with magnetic field strength comparable to bulk processed magnets. The magnetic properties dependence on the thickness (t) of glass insulation has revealed the following data: Film prepared without insulation produced a randomly oriented film with coercivity (iHc) around 480 kA/m, remanence value (Mr) around 0.67 T, MrMs=0.48 and (BH) max around 73 kJ/m3. While on the other hand, the films on substrates with insulation thickness of t=0.1, 0.2, 0.3, 0.6, 0.8 and 1.3 mm, magnetic properties of 4πMr= 0.67-0.93 T, iHc=1082-1290 kA/m, Mr/Ms=0.52-0.96 and a (BH) max=80-167 kJ/m3, were found.
    Download PDF (879K)
  • T. Kato, K. Sugihara, H. Ito, A. Kobayashi, Y. Fujiwara, S. Iwata, S. ...
    2002 Volume 2 Issue 2 Pages 98-103
    Published: May 01, 2002
    Released: August 25, 2010
    JOURNAL FREE ACCESS
    Magnetic circular dichroism (MCD) spectra were measured for sputter-deposited Mn1-xCrxPt3 and MBE-grow CrPt3 films. Applying the magneto-optical sum rules, it was found that the moment ratio <Lz> / 2 <Sz> of Cr is very large compared with that of Mn. The moment ratios for Cr and Mn are almost independent of the composition x. In the CrPt3 filmgrown epitaxially on MgO (111) substrate, the orbital moment was found to be small compared to that of the polycrystalline films. A close relationship was foundbetween the perpendicular magnetic anisotrop and the orbital moment.
    Download PDF (822K)
  • G Lauhoff, T Suzuki, R Sbiaa
    2002 Volume 2 Issue 2 Pages 104-109
    Published: May 01, 2002
    Released: August 25, 2010
    JOURNAL FREE ACCESS
    The field dependence of activation volume (Va) is determined by four different methods for longitudinal recording media. For two methods using the irreversible magnetization, Va increases with reversing fields up to the coercivity (Hc). The Va determined from the time dependence of the total magnetization, which includes the reversible magnetization, yields the opposite behavior. The Va is much larger at lower fields and decreases with reversing fields up to Hc. This difference is attributed to a difference between the total and irreversible magnetization, which is particularly significant for small reversing fields. Around Hc, the different methods yield comparable results. Furthermore, Va is found to strongly depend on time.
    Download PDF (1124K)
feedback
Top