The effective write-track widths of three different thin-film heads, a high-B_s head and two permalloy heads with different gap-depths, were studied by using a Co-Cr-Ta-sputtered disk. The off-track performances of the output amplitude and media noise were investigated. The effective write-track width of the permalloy head with a small gap-depth was found to be the smallest because of the magnetic saturation on both sides of the head-pole-tip edges. Furthermore, by observing the Bitter patterns, it was found that the transition width at the edges of the magnetic transition region in the disk is wider than that at the center. This phenomenon is caused by the wider distribution of the write field at the head-pole-tip edges. This tendency becomes more marked with increasing recording density. However, the high-B_s head allows a large effective write-track width, because it prevents head-pole-tip saturation. Therefore, the high-B_s head has the potential for magnetic recording with higher TPI.

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  The temperature dependence of the anisotropy field and anisotropy constants of Sm₂Fe₁₇N₃ was evaluated from the calculated magnetization curves, using crystal field parameters obtained in a previous study. The anisotropy field of Sm₂Fe₁₇N₃ at 0 K was estimated to be 750 kOe; this estimate was confirmed by pulsed-field magnetization measurements up to 1100 kOe. The coercivity of Sm₂Fe₁₇N₃ magnets was found to be strongly influenced by the maximum applied field. This fact indicates that the coercivity of Sm₂Fe₁₇N₃ magnets is nucleation-controlled. The coercivity of Sm₂Fe₁₇N₃ magnets increased monotonically with decreasing temperature, except in the case of a zinc-bonded magnet (30 wt% Zn). The relationship between the coercivity and the magnetocrystalline anisotropy of Sm₂Fe₁₇N₃ is discussed.

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  This paper presents a push-pull variable inductor for lagging reactive power control. The inductor is constructed with a pair of orthogonal-cores, and the output current is almost sinusoidal over a wide control region. Application of the inductor in a three-phase system is discussed. The experimental and analytical results show good agreement.

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  The structure and magnetic properties of Fe-M-B (M=Ta, Hf, Ti, Nb, Zr) alloy films produced by rf sputtering were investigated. A mostly single bcc phase with a nanoscale grain size of about 10 nm was found to be formed by annealing these sputtered amorphous films. The good soft magnetic properties seem to result from the decrease in the apparent magnetic anisotropy caused by the formation of a nanocrystalline bcc structure and by the reduction in the magnetostriction due to dissolution of M and B into the bcc phase. The Fe content of the composition to obtain an excellent soft magnetic property in the alloy film with a large atomic radius of M element rises and the value of B_s obtained as a result grows. A high permeability (μ) of 1350 to 3460 at 1 MHz combined with a high saturation magnetization (B_s) of 1.42 to 1.64 T was obtained for Fe_76.8Ta_6.6B_16.6, Fe_87.9Hf_9.8B_2.3, Fe_78.5Nb_8.3B_13.2, and Fe_89.6Zr_7.7B_2.7 by annealing the amorphous films for 3.6 ks at 873 K or 923 K.

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  The soft magnetic properties of a nanocrystalline bcc Fe₉₀Zr₇B₃ alloy with a Co substitution obtained by annealing a melt-spun amorphous phase were investigated. The addition of Co to the nanocrystalline Fe-Zr-B alloy causes an increase in permeability. This is presumed to be due to an increase in the exchange coupling between individual bcc grains resulting from an increase in the Curie temperature of the residual amorphous phase as well as a reduction of magnetostriction. The influence of the residual stress, which is caused by molding the samples in epoxy resin, on the magnetic core properties was examined for the nanocrystalline Fe-Co-Zr-B alloys. A low core loss of 66.6 W /kg at 100 kHz and 0.2 T was confirmed for a zero magnetostrictive (Fe_0.985-Co_0.015)₉₀Zr₇B₃ sample with a saturation magnetization of 1.64 T under a residual stress of －1.4 × 10⁸ Pa.

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  Noise filter characteristics of a common-mode choke coil fabricated from a nanocrystalline Fe₈₄Nb₇B₉ alloy were investigated with the aim of clarifying its potential for application as a core material. The impulse attenuation characteristics of the choke coil with the nanocrystalline alloy core were found to be superior to those of one with an Mn-Zn ferrite core. The choke coils made from the nanocrystalline alloy and the amorphous alloy cores showed higher attenuation in the frequency f range above 1 MHz. The common-mode attenuation of the choke coil with the nanocrystalline alloy core exhibited attenuation values higher than those of the ones with the other two cores in the frequency f range above 4 MHz. The conducted radio noise characteristics of the choke coil with the nanocrystalline alloy core were confirmed to be superior to those of the one with the amorphous alloy core. The attenuation of the former was 5 dB higher than that of the latter.

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  The domain-refining effect of linear grooves introduced into the surface of grain-oriented silicon steel was analyzed on a basis of a 180° domain wall scheme. The stable domain wall spacing was calculated by minimizing the sum of the domain wall energy and the magnetostatic energy arising from the free magnetic charges occurring along the groove edges. The results of the calculation showed that the wall spacing depends heavily on the depth, pitch and angle of the grooves but only negligibly on the groove width in the range of the present consideration. The eddy-current loss calculated using the Pry and Bean theory was compared with the experimental results, and it was found that the loss was in qualitative agreement with the results; the numerical discrepancy can be attributed to uneven magnetization around the grooves.

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  The structure and magnetoresistance (MR) of granular Fe/Ag alloy films produced by an ion-cluster-beam technique have been observed. Small-angle X-ray scattering and transmission electron micro-scope measurements show chemical fluctuation in the range of 15 nm and small Fe clusters about 5 nm in diameter. At 4.2 K, an MR effect is very large between 10 and 40 at%Fe, with the maximum MR value at around 20-30 at%Fe. When the Fe concentration increases from the Ag-rich side, the electrical resistivity rapidly increases at around 50 at%Fe. These features are ascribable to the geometrical and magnetic percolations of the Fe clusters. The field dependence of the MR is composed of saturation-type and non-saturation-type contributions, even at 140 kOe, indicating the contributions of large Fe clusters, small Fe atoms and molecules in the Ag-rich matrix, and Fe atoms located at the interfaces between Fe clusters and Ag matrix.

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