Transactions of the Magnetics Society of Japan
Online ISSN : 1884-6726
Print ISSN : 1346-7948
ISSN-L : 1346-7948
Volume 5 , Issue 1
Showing 1-9 articles out of 9 articles from the selected issue
  • W-X. Xia, T. Yamada, K. Tani, J. Numazawa, H. Aoi, H. Muraoka, Y. Naka ...
    2005 Volume 5 Issue 1 Pages 1-4
    Published: February 01, 2005
    Released: May 18, 2010
    JOURNAL FREE ACCESS
    The media magnetization, which was based on magnetic particle models, was introduced into the 3 dimensional finite element method using the commercial software JMAG-Studio. The head-medium interaction was accurately taken into account for the single pole head and double layer media perpendicular magnetic recording system. In order to deal with the medium movement, a regular mesh partition was realized. The effect of the single pole head structure on the recording resolution was investigated by using the newly developed program. It was found that a trailing-side return path structure in the down-track direction and a side-shield structure in the cross-track direction could significantly decrease the transition width and the track width, respectively.
    Download PDF (752K)
  • Y. Kimishima, T. Sasaki, M. Uehara, Y. Satoh
    2005 Volume 5 Issue 1 Pages 5-8
    Published: February 01, 2005
    Released: May 18, 2010
    JOURNAL FREE ACCESS
    Magneto-resistance (MR) ratios were measured for (Fe3O4) 1-χ (CrO2) χ, granular systems between 77 K and 300K, where x is the volume fraction of CrO2 in the measured sample. Since the spin polarization of conduction electrons is -100% in Fe3O4 and 100% in CrO2, the present granular junctions were expected to show inverse tunneling magnet -resistance (TMR) effects. In the range 0 ≤χ≤ 1, MR behaviors were characterized by low-resistive CrO2/I/CrO2 junctions, where “I” denotes some insulating barrier. For χ≤ 0.2, the magnetic conduction behaviors were dominated by the presence of high-resistive Fe3O4/I/Fe3O4 junctions. The inverse TMR effect only appeared at χ = 0.3 near the percolation threshold χc of CrO2/I/CrO2 paths, where the number of CrO2 grains completely enclosed by Fe3O4 grains became maximum. An averaging effect on the coercive force Hc caused by randomly magnetic anisotropy was also observed for the present granular system.
    Download PDF (950K)
  • C. C. Yu, Y. D. Yao, S. C. Chou, Y. Liou
    2005 Volume 5 Issue 1 Pages 9-12
    Published: February 01, 2005
    Released: May 18, 2010
    JOURNAL FREE ACCESS
    In this study, we present a method for fabricating magnetic dots array through nanosphere lithography and reactive-ion etching. Through this technique, one can control the magnetic dot size by tuning the etchingtime of nanospheres. As a demonstration, [Co (3Å)/Pt (10Å)] 15 films and dots were fabricated on Al2O3 (0001) with Pt (111) buffer layers at 100°C. The measurement of polar magneto-optical Kerr effect showed a perpendicular magnetic anisotropy in both cases and a low squareness in Co/Pt nanodots system. The investigation of magnetic force microscopy showed that Co/Pt nanodots displayed a single domain behavior.
    Download PDF (974K)
  • G. Kimura, T. Ohsawa, H. Itoh, J. Inoue
    2005 Volume 5 Issue 1 Pages 13-17
    Published: February 01, 2005
    Released: May 18, 2010
    JOURNAL FREE ACCESS
    The tunnel magnetoresistance (TMR) of ferromagnetic junctions including twisted magnetization near the insulator barrier has been theoretically studied using linear response theory and a single orbital tight-binding model. The region of the twisted magnetization has been found to have a large effect on TMR only when the twisted magnetization region is several atomic layers. This agrees with experimental results.
    Download PDF (791K)
  • Qingyu Xu, Yasuyuki Kageyama, Takao Suzuki
    2005 Volume 5 Issue 1 Pages 18-21
    Published: February 01, 2005
    Released: May 18, 2010
    JOURNAL FREE ACCESS
    FePt and CoPt particles were successfully fabricated by ion beam induced chemical vapor deposition (IBICVD) with a focused ion beam (FIB) system. The as-deposited FePt particles are amorphous, while the CoPt particles are crystallized in fcc structure. After annealed at 600°C for 1 hour in high vacuum chamber, the FePt particles are crystallized in fcc structure, and the crystallization structure of CoPt particles is improved. Magnetic force microscopy (MFM) was used to study the magnetic domain patterns of FePt and CoPt particles. Concentric domain pattern was observed in the as-deposited and annealed FePt particles. For the as-deposited CoPt particles, no magnetic domain pattern was observed. For the annealed CoPt particles, after applying 20 kOe magnetic field perpendicular to the substrate plane, the particles also show the concentric magnetic domains. It is suggested that the in-plane component of the magnetization will follow the circular boundary of the particles, which results in a circular domain structure. The observed concentric domain pattern is due to the alternately up and down, out-of-plane components.
    Download PDF (1806K)
  • K. Shintaku, S. Watanabe
    2005 Volume 5 Issue 1 Pages 22-34
    Published: February 01, 2005
    Released: May 18, 2010
    JOURNAL FREE ACCESS
    A variety of additives and underlayers were examined to obtain good soft magnetic properties for Fe-Co system films with a high saturation magnetic flux density (Bs) of the 2.4 T class. It was found that Al2O3 is an excellent material for use as an additive. The continuous columnar structure of the film is formed by Al2O3 segregated in the grain boundaries from the initial growth layer up to the top layer. The lattice spacing of Fe-Co films was expanded by Al2O3 addition. The small grains in the initial growth and the random crystal orientation due to the presence of an underlayer are also important factors in obtaining good soft magnetic properties for Fe-Co system films. An Hch (Hc in the hard axis direction) value of less than 1 Oe was obtained only by using a combination of Al2O3 addition and an fcc structure underlayer film in a wide range of film thicknesses. The mechanism whereby soft magnetic properties are obtained in Fe-Co system films seems to be partially explained by the combination of Hoffman's ripple theory and the exchange-induced ripple reduction process.
    Download PDF (3695K)
  • T. Liu, H. Kikuchi, K. Ara, Y. Kamada, S. Takahashi
    2005 Volume 5 Issue 1 Pages 35-38
    Published: February 01, 2005
    Released: May 18, 2010
    JOURNAL FREE ACCESS
    A magnetic probe containing a Hall sensor and pickup coil was developed, and its accuracy was confirmed by comparison with standard ring sample results under zero stress. The magnetic minor hysteresis loops of a lowcarbon steel plate sample were measured by using this probe under uniaxial tensile stresses. It was found that both the coercivity Hc and hysteresis loss WF can be measured accurately by means of a magnetic probe. In the perfectly elastic region, from 0 to 90 MPa, Hc and WF decrease with increasing external stresses due to domain re-orientation, and they start to increase a little in the micro-plastic range. In the plastic stage, Hc and WF increase almost linearly with external stresses as a result of dislocation pinning effects. This clear relationship between magnetic properties and external stresses is also valid for NDE applications.
    Download PDF (671K)
  • H. Tian, S. Yamada, M. Iwahara, H. Tooyama, K. Miya
    2005 Volume 5 Issue 1 Pages 39-42
    Published: February 01, 2005
    Released: May 18, 2010
    JOURNAL FREE ACCESS
    Eddy-current testing (ECT) has been widely applied in manufacturing to the inspection of defects inside conducting materials. It, however, is still difficult to obtain accurate depth information on deep cracks and to detect cracks on the reverse sides of thick structures by using the technique. We conducted a theoretical analysis based on 3-D solutions of Maxwell equations to determine the optimum exciting frequencies and suitable positions of a sensor for both depth detection and reverse-side detection. An ECT probe consisting of a single-direction exciting coil with a spin-valve-type giant magnetoresistive (SV-GMR) sensor was employed in experimental inspection of 12-mm-and 22-mm-thick stainless steel (SUS) plates with 67% deep and 77% deep cracks, respectively. The experimental results show good agreement with our theoretical analysis. Thus it is confirmed that both the ECT probe and the theoretical analysis proposed in this paper are capable of detecting defects in a thick SUS plate.
    Download PDF (757K)
  • H. Yaguchi, S. Sasaki
    2005 Volume 5 Issue 1 Pages 43-48
    Published: February 01, 2005
    Released: May 18, 2010
    JOURNAL FREE ACCESS
    We previously proposed a novel micro-actuator that provides propulsion using the mechanical resonance energy of a system excited by an electromagnetic force, allowing relatively high speeds. Long-distance movement proved difficult, however, because of the need for a power supply cable. In this paper, we propose a new cable-free actuator with a mechanical dc-ac micro-inverter that can move a long distance. The mechanical dc-ac inverter incorporates a double cantilever beam that switches under an electromagnetic force. The prototype actuator is capable of moving inside a very small pipe 10 mm in diameter. Experimental results show that the actuator can move upwards at a speed of 5.1cm/s. This cable-free actuator has many possible applications, including small pipe inspection and maintenance.
    Download PDF (997K)
feedback
Top