We have investigated the synthesis conditions and magnetic properties of Fe substituted hibonite with initial compositions of CaAl_12-xFe_xO₁₉ (0≤x≤12) and CaAl_10-xFe_xO_19-δ (0≤x≤10). The Fe doped hibonite can be synthesized at a sintering temperature of 1300˚C. The X-ray diffraction patterns of Fe substituted hibonite samples are in good agreement with the pattern of hibonite. The lattice parameter increased due to the difference between the radius of Al³⁺ and that of Fe³⁺. The magnetization and Curie temperature of the best sample (CaAl₂Fe₈O_19-δ) are 31 emu/g and 290˚C, respectively.

  A highly sensitive probe based on the skin effect was developed to measure thin film permeability. A new microstrip-line-type probe on a flexible substrate was fabricated and placed in contact with a magnetic thin film. The probe enhanced the signal-to-noise ratio and broadband measurement. The permeability of amorphous CoNbZr film (25 mm × 25 mm, 5 nm thick) and that of CoFeB film (45 mm × 25 mm, 0.5 μm thick) were optimized. The measured values were in rough agreement with theoretical values based on the Landau–Lifshitz–Gilbert equation and eddy current generation up to 40 GHz.

  We propose a magneto-optical (MO) color imaging technique that enables magnetic field distributions to be quantitatively observed in real-time. Values of magnetic fields are displayed as colors. MO imaging plates have been developed using highly bismuth-substituted neodymium iron garnet films, for use in MO color imaging. The films were prepared by the metal-organic decomposition method. The MO imaging plates were characterized using the MO figure of merit for MO imaging plates, which is defined in this study. The magnetic fields were expressed by colors, using light-emitting diodes (LEDs) as light sources. The colors varied from blue to yellow, from green to yellow, and from blue to red, for sources corresponding to a white LED, combined green and yellow LEDs, and combined blue and yellow LEDs, respectively. The MO color imaging of spherical magnets is demonstrated.

  A fast magnetization reversal accompanied by a large Barkhausen jump in a magnetic wire is utilized in speed sensors, rotation sensors, and other applications. This magnetization reversal induces a pulse voltage in a pick-up coil, which can also be applied for electricity generation as an energy-harvesting element. Dependence of the output voltage on the position of the pick-up coil indicated a fast magnetization reversal by a domain wall propagation. An excitation method for a vibration-type electricity-generating element using a single magnet was optimized by changing the magnet size. The output voltage obtained from the FeCoV wire depended on the amplitude of vibration of an excitation magnet. In order to minimize the vibration amplitude of an excitation magnet required for generating the output voltage, a field distribution from magnets of various sizes was calculated. It was found that just a 0.6 mm-movement of an NdFeB magnet was sufficient to generate the output voltage.

  Magnetocardiogram (MCG) measurement systems require noise reduction, because MCG signals are extremely small compared to environmental magnetic noise. We investigate the efficacy of a novel noise-reduction method, based on an independent component analysis (ICA). The proposed noise reduction method requires a component selection process to distinguish signal from noise. A major challenge in applying ICA-based noise reduction method is the selection of suitable parameters, which in practice is often performed manually with rather subjective parameter choices. To address this issue, we proposed a component selection method that can be performed quantitatively and automatically. The proposed method is based on the peak values of the autocorrelation function and helps distinguish the independent components of the MCG signals from the noise using an appropriate threshold. By using the proposed method, we obtain output signal-to-noise ratios (SNRs) of 33.98 dB, 19.17 dB, and 13.56 dB, corresponding to input SNRs for the simulated data at respectively 0 dB, -10 dB, and -20 dB, after noise reduction. The results show that the proposed method exhibits remarkable promise in extracting a noise-mitigated MCG signal for a wide range of SNRs.