Journal of the Magnetics Society of Japan
Online ISSN : 1882-2932
Print ISSN : 1882-2924
ISSN-L : 1882-2924
Current issue
Displaying 1-3 of 3 articles from this issue
Magnetic Recording
  • T. Kobayashi, I. Tagawa
    2024 Volume 48 Issue 3 Pages 40-46
    Published: May 01, 2024
    Released on J-STAGE: May 01, 2024
    Advance online publication: April 09, 2024
    JOURNAL OPEN ACCESS

      We discuss the influence of design parameters on adjacent track interference (ATI) in 4 Tbpsi heated-dot magnetic recording where the parameters are the mean Curie temperature, Curie temperature variation, anisotropy constant ratio, dot size variation, Gilbert damping constant, writing field magnitude, and writing field angle. We calculate the dot height to achieve a bit error rate of 10-3 after adjacent track writing as a function of the design parameters. The dot height must be increased when we choose a lower mean Curie temperature, since the thermal gradient decreases simultaneously. The adjacent track temperature is related to the Curie temperature variation via the writing temperature. ATI is strongly affected by the anisotropy constant ratio. The dot height must be increased as the dot size variation increases, since the probability of a small dot appearing increases. The Gilbert damping constant has an effect on ATI. Since a writing field magnitude of 10 kOe is relatively small against the anisotropy field, the increase in the dot height is relatively small when the writing field magnitude increases from 10 to 15 kOe or the writing field angle changes from 180 to 135 deg.

    Download PDF (757K)
Biomagnetism / Medical Applications
  • M. Washino, K. Nomura, T. Matsuda, S. Seino, T. Nakagawa, T. Kiwa, A. ...
    2024 Volume 48 Issue 3 Pages 47-52
    Published: May 01, 2024
    Released on J-STAGE: May 01, 2024
    Advance online publication: April 09, 2024
    JOURNAL OPEN ACCESS

      Increased fluid viscosity in vivo is associated with diseases such as hypertension, atherosclerosis, and cancer. Fortunately, viscosity distribution enables pathological diagnosis. Magnetic-particle imaging (MPI), which detects the high-frequency magnetic field response of magnetic nanoparticles (MNPs) for obtaining highly sensitive images, can be applied to viscosity mapping to obtain a solvent viscosity distribution based on the relaxation time of MNPs. In this study, we assessed the relaxation time differences of MNPs in media with varying viscosities, detected as phase differences in the signal using an MPI system. The differences, which increases with more viscosity, differ depending on the particle size and the magnetic properties of the magnetic nanoparticles.

    Download PDF (852K)
  • M. Takahashi, M. Fushimi, S. Yabukami, M. Sekino, A. Kuwahata
    2024 Volume 48 Issue 3 Pages 53-59
    Published: May 01, 2024
    Released on J-STAGE: May 01, 2024
    Advance online publication: April 09, 2024
    JOURNAL OPEN ACCESS

      Magnetic resonance imaging (MRI) is a noninvasive medical imaging technology with a high spatial resolution. We aim to design a single-channel radiofrequency receive coil with an optimized signal-to-noise ratio (SNR) for various field intensities in MRI. We propose a method that maximizes the SNR through surface current optimization using the target field method. The proposed method can design a dedicated coil shape by solving an objective function with terms related to the signal, coil resistance noise and sample resistance noise. We found coil shapes for a rat kidney model in the case of static magnetic field intensity |B0| = 7 T, 0.3 T and 6.5 mT as an example. Our method will enable the design of single channel receive coil for preclinical applications of small animals.

    Download PDF (1382K)
feedback
Top