Transactions of the Magnetics Society of Japan
Online ISSN : 1884-6726
Print ISSN : 1346-7948
ISSN-L : 1346-7948
Volume 4 , Issue 1
Showing 1-9 articles out of 9 articles from the selected issue
  • A. Kikitsu, Y. Kamata, H. Hieda, M. Sakurai, K. Asakawa, K. Naito
    2004 Volume 4 Issue 1 Pages 1-8
    Published: February 01, 2004
    Released: May 18, 2010
    JOURNAL FREE ACCESS
    A new method for fabricating a patterned magnetic recording medium is presented. This method uses the self-assembling phenomenon of the diblock copolymer. A tetragonal array of ordered polymer dots is aligned by a circumferential groove pattern on a disk substrate. The groove pattern is transferred from a Ni master plate by a nanoimprinting process. CoCrPt patterned media with a dot pattern were fabricated using this method (artificially aligned self-assembling (AASA) method). The dot size was about 40 nm in diameter. Magnetic estimations showed the single-domain CoCrPt dots with good magnetic isolation. The patterned medium showed a perpendicular magnetic orientation induced by the crystalline anisotropy. TEM observation revealed little physical damage in CoCrPt dots though an ion milling process was employed for etching the magnetic layer. Degradation in the magnetic anisotropy energy was also found to be slight by the estimation with a micromagnetic simulation. A master plate with the AASA pattern has been developed. This removes the annealing process from the fabrication process and improves the throughput. Pattern transfer of the AASA master into the photopolymer layer was successful.
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  • M. Arita, K. Hamada, T. Ono, A. Okada
    2004 Volume 4 Issue 1 Pages 9-12
    Published: February 01, 2004
    Released: May 18, 2010
    JOURNAL FREE ACCESS
    Magnetic microstructure and magnetoresistance (MR) were simultaneously investigated for an Ni0.8 Fe0.2 film with dimensions of 2mm× 100μ m× 35nm. An in-situ experiment in a magnetic field was carried out by simply tilting the film inside a transmission electron microscope. Using the ripple contrast of Lorentz images as a guide, the inhomogeneous distribution of the magnetization was investigated. Comparing the result obtained by Lorentz microscopy with the magnetoresistance of the film, we quantitatively investigated the distribution of the MR-curve within the film. The influence of the film edge on the MR-curve extended to 20μ m from the edge. The feasibility of simultaneous in-situ experiments involving Lorentz microscopy and magnetoresistance measurements was confirmed.
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  • C. Mitsumata
    2004 Volume 4 Issue 1 Pages 13-16
    Published: February 01, 2004
    Released: May 18, 2010
    JOURNAL FREE ACCESS
    Thermal fluctuation of fine magnetic particles with L10 -type structure is investigated within the framework of Monte Carlo calculations. The thermal fluctuation of spins is strongly influenced by the demagnetizing field at higher temperatures, that is, the reduction of the magnetic anisotropy energy becomes larger at higher temperatures.
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  • Y. Kimishima, M. Uehara, Y. Satoh, T. Sasaki
    2004 Volume 4 Issue 1 Pages 17-20
    Published: February 01, 2004
    Released: May 18, 2010
    JOURNAL FREE ACCESS
    Magneto-resistances (MR) were measured at 77 K and 300 K for spin-polarized half-metallic ferromagnet CrO2 nano-granular samples. They were prepared from the precursor of CrO3 in a micro-reactor at temperatures between 598K and 723K under oxygen gas pressures of 0.5 and 10 MPa. Room temperature MR ratios of -0.13 to -0.45% and 77 K MR ratios of -2.3 to -3.4% were observed for CrO2 with Cr2O5 and/or Cr2O3 impurities. The results showed that the Cr205 forms well tunnel barriers between CrO2 nano-grains, probably due to the weak magnetic property at 300K.
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  • Y. Kageyama, T. Suzuki
    2004 Volume 4 Issue 1 Pages 21-23
    Published: February 01, 2004
    Released: May 18, 2010
    JOURNAL FREE ACCESS
    Co particles were fabricated by means of a focused ion beam (FIB) system with dicobalt octacarbonyl precursor. Precursor vapor was introduced into the specimen chamber and irradiated with a Ga+ ion beam having a diameter of several tens of nanometers through vector scan rastering. An attempt was made to confirm the effect of a single beam incidence on the Co dot size.
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  • H. Sakuma, H. Nishio, Y. Kitamoto, Y. Yamazaki, H. Yamamoto
    2004 Volume 4 Issue 1 Pages 24-27
    Published: February 01, 2004
    Released: May 18, 2010
    JOURNAL FREE ACCESS
    Two methods using torque measurement in magnetic fields of up to 90 kOe were applied to evaluating the magnetocrystalline anisotropy of FePt nanoparticle samples with various order parameters. The maximum anisotropy field in the samples was obtained from the rotational hysteresis loss measurement. It was shown that the maximum anisotropy field monotonically increases with the order parameter. The magnetic anisotropy constant corresponding to the maximum anisotropy field of the sample with an order parameter of 0.96 is 4.4×107erg/cm3. The anisotropy field distribution was also obtained by using Flanders and Shtrikman's method. Thermal relaxation of magnetization was, however, superimposed on the anisotropy field distribution at 300 K.
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  • M.B.A. Jalill, C.W. Kim, Y. Takemura, J. Shirakashi
    2004 Volume 4 Issue 1 Pages 28-33
    Published: February 01, 2004
    Released: May 18, 2010
    JOURNAL FREE ACCESS
    We model the combined effects of Coulomb blockade (CB) and spin-dependent tunneling in a nanoscale planar-type Ni/NiO double-junction, based on the geometry of a proposed experimental structure. Rectangular and disk-shaped island electrodes, of a size range of w =10 to 50 nm are considered. Precise determination of the circuit capacitances is performed using finite-element (FE) methods. The calculated capacitance values differ significantly from those obtained using analytical formulae. For instance, the island self-capacitance Cs values are about five times larger, which means that the operational temperature for the CB device is seriously over-estimated by the analytical formulae. The capacitance calculations also show that an extended gate covering both the island and the contact electrodes, can improve the gate sensitivity by 95% with only a minimal increase (0.3%) of the selfcapacitance Cs. This avoids the need for an ultrasmall gate lithographed exactly below the island in the double junction device. The tunneling current is then obtained using the calculated capacitance values, and incorporates both single tunneling and cotunneling. Finally, we present the temperature dependence of the I-V and I-Vg characteristics and TMR values which, being based on actual fabricated dimensions, will be significant for comparison with experimental results.
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  • E. Suzuki, S. Arakawa, H. Ota, K-I. Arai, R. Sato
    2004 Volume 4 Issue 1 Pages 34-38
    Published: February 01, 2004
    Released: August 04, 2010
    JOURNAL FREE ACCESS
    We propose a new type of optical probe designed to detect magnetic near-fields with high accuracy up to the gigahertz range. The probe consists of a loop antenna element and a bulk electro-optic crystal. It requires no metallic cable or balun. We examined probe characteristics for magnetic field detection up to 10 GHz. We confirmed that the probe can measure a magnetic field distribution near a microstrip line with high accuracy in gigahertz range.
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  • K. Chomsuwan, Y. Fukuda, S. Yamada, M. Iwahara, H. Wakiwaka, S. Shoji
    2004 Volume 4 Issue 1 Pages 39-42
    Published: February 01, 2004
    Released: May 18, 2010
    JOURNAL FREE ACCESS
    This paper proposes the utilization of a GMR sensor as a magnetic sensor of an eddy-current testing probe for the detection of defects in printed circuit boards. The proposed probe consists of a meander coil functioning as an exciting coil and a GMR sensor functioning as a magnetic sensor. The GMR sensor has the advantages of high sensitivity to low magnetic fields over a broad range of frequency and very small size, and is therefore very useful for detecting very small cracks in printed circuit boards by means of the eddy-current testing technique. This paper describes the structure of the proposed probe, the inspection principles, and the experimental results achieved with an eddy-current testing probe using a GMR sensor in comparison with one using a solenoid coil senso
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