The effect of spacing between master and slave media on printing characteristics was investigated in this study by using micromagnetic simulation. The results indicated that the printing characteristics were improved as the spacing decreased. At the optimal printing magnetic field, the effect of the spacing for checker pattern was larger than that for L/S pattern. Decreased in the spacing expanded the tolerance region in which superior printing characteristics were obtained. Moreover, decreased in the spacing also expanded the overlap region between tolerance regions for two patterns.

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  Statistical investigations into off-track errors for shingled and conventional writing were carried out to reveal error behavior at high track densities. The residual data width in shingled writing tended to be wider than that in conventional writing for the same average track pitch. A comparison of the distributions of the calculated residual data width revealed that for conventional writing erroneous tracks were generated when the track was squeezed by both neighboring tracks, i.e., double squeezing. Shingled writing has an advantage in that this double squeezing does not occur and therefore a higher track density can be achieved.

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  Controlling metal magnet with electric field opens up a new pathway to fabricate metallic nonvolatile magnetic data-storage devices. Such magnetoelectric coupling has been studied mainly for insulators, e.g. complex multiferroic oxides. Although electric field applying to the bulk metals cannot go inside due to the screening by the conducting electrons, we found that magnetic phase of nano-scale iron metal magnets is able to be controlled by electric field pulses. All experiments were performed by scanning tunneling microscopy (STM) setup in ultra-high vacuum at 4K. Statistic switching of the magnetic phase between ferromagnetic bcc phase and layer-wise antiferromagnetic fcc phase as well as time response of the phase switching by a fast pulse were studied.

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  A flat-patterning method that exploits ferromagnetic (FM)-antiferromagnetic (AF) transition in [001]-oriented L1₀ FePt_1-xRh_x films was investigated. FM-AF patterns with several dot diameters (D) were fabricated by locally diffusing a small percentage of FePt atoms onto the FePt_1-xRh_x film. The geometric and magnetic properties of the patterns were analyzed in detail. Only areas whose composition crossed the FM-AF threshold underwent a magnetic phase change to the FM phase. FM dots with single-domain structures were observed by magnetic force microscopy in the AF matrix in a range of D ≤ 100 nm.

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  Magnetic force microscope (MFM) tips were prepared by coating Si tips of 5 nm radius with 3d ferromagnetic transition metals (Ni, NiFe, Fe, and Co). The effects of coated-film thickness and coating material on the MFM signal sensitivity and resolution were investigated. As the film thickness increases, the sensitivity increases due to the increase of magnetic volume of tip. Higher sensitivity is observed for the same film thickness in the order of tip coated with material with higher remanent magnetization, Ni < NiFe < Fe < Co. Resolutions of 14.0, 13.4, 10.6, and 9.1 nm are obtained with tips coated with 40-nm-thick Ni, 40-nm-thick NiFe, 20-nm-thick Fe, and 20-nm-thick Co films, respectively. As the film thickness further increases, the resolution decreases due to the increase of tip radius. The MFM resolution is influenced by both the remanent magnetization of coating material and the tip radius. Bit lengths of around 28 nm of an HDD medium with 528 Gb/in² area density are clearly observed by employing the tips coated with 20-nm-thick Fe and 20-nm-thick Co films. A positioning technique of MFM observation of a same area for high-density magnetic recording media is also proposed.

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  We developed a frequency-controlled inverter power supply for spot welding machines. The welding currents reached 10 kA or higher, while impedance at the weld was extremely small, at 1 mΩ or less. These conditions demanded welding power supplies capable of providing low voltage at high current. To develop such a power supply, we investigated how to control the welding current using an inverter power supply by installing an internal transformer with a large winding ratio. However, due to issues concerning the global environment and energy conservation, inverter power supplies require increasingly higher efficiency. One method of improving efficiency is to match the impedance between the inverter power supply and the load. The leakage impedance of the inverter transformer, however, is dependent on frequency and current. In addition, the extremely low load (1 mΩ or less) makes such impedance matching difficult to implement. This paper presents the results of an investigation into high-efficiency power control between an inverter power supply with an internal transformer (with a large winding ratio) and a load of no more than 1 mΩ. The results confirmed that inverter output power that maximized frequency and matching were possible.

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  Magnetic gears can transmit torque without mechanical contact. They therefore have low vibration and acoustic noise, and are low maintenance in comparison with conventional mechanical gears. Various types of magnetic gears have been introduced. A planetary type magnetic gear has attracted interest recently because of its higher transmission torque compared to other types, and it is expected to be put into practical use. However, it is necessary to reduce the eddy current loss caused by harmonic fluxes in the air gap. This paper presents a magnetic gear using polar anisotropic Nd-Fe-B bonded magnets in which the eddy current is rarely induced.

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  A reluctance network analysis (RNA) model of a permanent magnet (PM) motor was presented in a previous paper and the iron loss of the stator core of the PM motor was accurately calculated by using this model. However, loss of eddy current in permanent magnets caused by carrier harmonics and slot harmonics was not discussed. This paper presents a method of calculating eddy current loss based on RNA by taking into consideration the magnetic reaction field caused by the eddy current. First, an electric network model for calculating eddy current is described. Next, the RNA model is presented by taking into account the magnetic reaction field by using magnetic inductance is presented. The validity of the proposed model is proved by comparing it with the finite element method (FEM) and an experiment.

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  Mobile devices are not sufficiently convenient yet because they need to be charged frequently. It is especially inconvenient when their battery power has slightly discharged. We have researched a contactless power transmission system (CLPS) for a station-type charger in mobile devices. This system can be installed in many types of mobile devices. We tested the transmission system of the station-type charger using a coil within a mobile device and confirmed that the system was effective and provided steady transmission of electrical power.

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  The iron losses and acoustic noises of a model transformer core made of grain-oriented electrical steel sheets were investigated under DC biased magnetization while altering the amplitude of magnetic flux density, B_m, and the DC biased magnetic field, H_DC, applied by the third windings. The iron loss increased as H_DC increased up to100 A/m, while over 100 A/m, the increment of iron loss by DC biased field rapidly decreased. The increase in iron loss at the same H_DC was largest at B_m:1.1−1.5 T. Meanwhile, the acoustic noise increased monotonically as H_DC increased. The acoustic noise of odd-order harmonics was drastically increased under DC biased magnetization, and this is the primary cause of the increase in acoustic noise.

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