In this study amorphous aluminum oxide (α-AlO) was used as an underlayer to crystallize c-axis oriented Ba-ferrite (BaM) film. But coercivity of these films was going to decrease sharply below 20 nm. A small amount of Al is added with BaM film with α-AlO underlayer. The substrate temperature (Ts) was kept at 550°C. Al content was varied from 0-4.5 atomic percent. Perfect c-axis orientation of BaM thin film is possible with a small addition of Al, even for the film of 10 nm with a δθ50 of 2.5°-2.8°. On the other hand, it was difficult to crystallize BaM/α-AlO film thinner than 25 nm. Coercivity of Al-BaM/α-AlO films in perpendicular direction was higher than that of BaM/α-AlO films, even for the thickness below 20 nm.

抄録全体を表示

A hot-upsetting process was applied to rapidly quenched starting ribbon powders having Nd₁₀Fe₈0Co₅B₅ alloy composition of the α-Fe/Nd₂Fe₁₄B system, with the aim of obtaining anisotropic exchange-spring magnets. Specimens fabricated at upsetting temperatures up to 950°C displayed isotropic magnetic properties, but anisotropic magnetic properties were manifested at 1000°C or higher. Specimens that exhibited anisotropy showed magnetic properties on the order of B_r = 0.3 T and H_cJ= 30 kA/m and consisted of a soft α-Fe magnetic phase and a hard Nd₂Fe₁₄B magnetic phase. Hard-phase crystals showed equiaxial morphology and reached a grain size of approximately 1μm. We observed from XRD patterns that the easy-magnetization axis of the hard-phase crystals tended to be oriented parallel to the direction of applied upsetting pressure.

抄録全体を表示

The repulsive-type magnetic bearing (RTMB) using permanent magnets for levitation and radial control enable system applications to be developed cheaply and simplify the control scheme. A balance system for mass measurement using RTMB was designed and fabricated in our laboratory. This system has some problems which generate an error in the measurement. It was found that the value of the error is large, and as a result, the system is less sensitive when it is used for measuring micro-masses. In this paper, the design of the previous system is modified to decrease the measurement error and increase the system's sensitivity to enable it to measure micromasses precisely. The configuration and operating characteristics of both the previous system and the modified one are explained. The experimental results confirm that the modified system can measure micromasses more precisely than the previous one.

抄録全体を表示

A small circulator with a coplanar waveguide structure was confirmed to have nonreciprocal transmission characteristics by a high-frequency electromagnetic simulation based on a three-dimensional finite element method. The circulator consists of a hexagonal YIG ferrite substrate and a Y-junction with coplanar waveguide transmission lines. Operating at 7 GH_z, the circulator has an insertion loss|S₂₁|of 0.69 dB, isolation |S₃₁| of 32.7 dB, retum loss |S₁₁| of 32.2 dB, and bandwidth of 77 MH_z. The nonreciprocal operation of the circulator is attributed to the wavy nonuniform distribution of the electric field in the YIG ferrite substrate.

抄録全体を表示

The transmission characteristics of a low-height circulator that we designed were simulated, using highfrequency electromagnetic analysis based on the finite element method. To reduce the height of the circulator, we dramatically reduced the thickness of the iron yoke and the ferrite magnet while maintaining the required magnetic bias field strength. The circulator has a hexagonal platelet shape with a diagonal line length of 7.5 mm and a height of 0.85 mm. It is composed of a 0.2-mm-thick ferrite magnet, a 0.3-mm-thick YIG ferrite platelet, a 0.17-mm-thick iron yoke, and a microstrip Y-junction. The simulation results exhibited acceptable nonreciprocal transmission characteristics with an insertion loss of 0.67 dB, and a return loss and an isolation both greater than 20 dB.

抄録全体を表示

With the goal of developing an artificial heart, a linear motion magnetic actuator has been produced and applied to a pump. The actuator is composed of two ring-shaped Nd-Fe-B magnets that face each other, the outer and inner diameters and thickness of which are 63mm, 17mm and 3mm, respectively. Rotating one of the magnets circumferentially via a motor produces reciprocating forces on the other magnet. The pumping motion is performed using the power of the reciprocating magnet. Because the actuator uses no windings, no copper loss, which causes heat generation in the body, is generated. The output powers of the actuator and the pump reached 1.03W and 0.65W, respectively.

抄録全体を表示