The sensitivity of magnetoresistance (MR) change was strongly influenced by the number of layers used in [NiFe (6 nm)/Cu (2.4 nm)/Co (6.0 nm)]_n. Experimentally obtained MR-H curves and M-H loops indicate that a sharp decrease in resistivity was mainly caused by 90°C coupling between magnetic layers, and the exchange coupling changed from 90°C coupling to bilinear coupling with an increase in the number of layers.

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The characteristics of magnetic contact duplication (MCD) in ultra-high-density magnetic recording were studied by extrapolation on experimental MCD data and by the use of magnetic transfer theory. Both the experimental data and the theoretical estimation show that the spacing between the mother and copy media can be estimated by summation of the surface roughnesses of both media in a condition of tight contact. The required spacing of both media was less than 1/20 of the recording wave-length. A non-oriented Ba ferrite medium (with susceptibility χ_x=χ_y=8), oriented Ba ferrite (χ_x=270, χ_y=1.5), and an evaporated metal (ME) medium χ_x=30, χ_y=20) showed respective gains of 1.5 [dB], 4 [dB], and 3 [dB] in magnetic transfer efficiency, compared with a conventional longitudinally oriented Co-γFe₂O₃ medium (χ_x=17, χ_y=1.5). One advantage of MCD was the symmetry of the reproduced wave form in digital recording, compared with that of head-recorded media. With related optimization of media, bias heads (using the transfer method), and the wavelength distribution, MCD in ultra-high-density recording will become practical.

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The orientation of acicular Fe particles in magnetic coating media was investigated by the use of a polarized light reflection technique. The particle volume fraction, φ_P, of the magnetic coatings was changed from 30.5 to 53.7 vol%. The reflection ratio was compared with the squareness of the hysteresis for the coatings, measured by VSM, indicating the maximum value when plotted as a function of φ_P. The reflection intensity was strongly influenced by the surface roughness of the magnetic coatings. At a value of φ_P=45.1 vol%, the particles were well dispersed in the media, with the result that the coating surface became very smooth. The orientation of particles in a magnetic paint was also expressed as a function of the angle between the electric vector of the polarized light and the direction of the applied magnetic field. However, the reflection ratio as a function of another volume fraction, φ_PL, of the magnetic paints decreased with an increase in the apparent viscosity of the magnetic dispersion.

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We observed the recorded bit structures (in the 10-300 kFCI range) and the magnetization distribution in the remanent state of Co-CoO obliquely evaporated films by using a spin-polarized scanning electron microscope. Uniformly distributed fine island domains (80-90 nm in diameter)were evident in the recorded bit region, but there were only a few island domains (about 130 nm wide) on the bit boundary. Similar island domains observed in the remanent state decrease the magnetostatic energy of the film.This leads to the creation of island domains in the recorded its in the same way as in the remanent state.

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