Artificial Periodic Magnetic Structures for Photonic and High Frequency Micro-magnetic Devices (original) (raw)
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Funtai oyobi fummatsu yakin, 2022
It has been empirically known that the coercivity of rare-earth permanent magnets depend on the size and shape of fine particles of the main phase in the system. Also, recent experimental observations have suggested that the atomic scale structures around the grain-boundaries of the fine particles play a crucial role to determine their switching fields. In this article, we review a theoretical attempt to describe the finite temperature magnetic properties and to evaluate the reduction of the switching fields of fine particles of several rare-earth permanent magnet materials based on an atomistic spin model that is constructed using first-principles calculations. It is shown that, over a wide temperature range, the spin model gives a good description of the magnetization curves of rare-earth intermetallic compounds such as R 2 Fe 14 B (R = Dy, Ho, Pr, Nd, Sm) and SmFe 12 . The atomistic spin model approach is also used to describe the local magnetic anisotropy around the surfaces of the fine particles, and predicts that the rare-earth ions may exhibit planar magnetic anisotropy when they are on the crystallinestructure surfaces of the particles. The dynamical simulation of the atomistic spin model and the corresponding micromagnetic simulation show that the planar surface magnetic anisotropy causes a reduction in the switching field of fine particles by approximately 20-30%, which may be relevant to the atomic scale surface effects found in the experimental studies.
Magnetic Materials and Semiconductors. A Concentrator Si Solar Cell Made by Low-cost Process
DENKI-SEIKO[ELECTRIC FURNACE STEEL], 2000
Obviously, concentrator solar cells reduce the total area of cells required, which provides lower system costs. For nonconcentrator solar panels, the solar cells represent 80% of the system cost. The use of concentrator cells provides a cost reduction for cells inversely proportional to the concentration ratio. However conventional Si concentrator cells normally require more complex photolithography which increases the cost of manufacture. In this novel approach a single step photolithography process is described which includes superfine random pyramid texture, with the electrode directly defined onto the textured surface. Additionally, improved electrode design was applied, allowing for operation under non-uniform surface voltage and current density, experienced during high concentrator conditions. This has lead to energy conversion efficiencies in excess of 19%. Experimental results on the conversion efficiency are in good agreement with the results calculated by the proposed equations taking into account of the distributed diode effect at high concentration ratio.
JSME Construction Standard for Superconducting Magnets of Fusion Facilities
Journal of High Temperature Society, 2009
The present paper describes the general view of the construction standard, which the Japan Society of Mechanical Engineers (JSME) has recently set up and published, for superconducting magnet structures to be used in nuclear fusion facilities. The present target of the standard is tokamak-type fusion energy facilities, especially the International Thermonuclear Experimental Reactor called ITER for short. The standard contains rules for structural materials including cryogenic materials, structural design considering magnetic forces, manufacture including welding and installation, nondestructive testing, pressure proof tests and leak tests of toroidal field magnet structures. The standard covers requirements for structural integrity, deformation control, and leak tightness of all the components of the superconducting magnets and their supports except for superconducting strands and electrical insulators. The standard does not cover deterioration which may occur in service as a result of corrosion, radiation effects, or instability of material. The standard consists of seven articles and twelve mandatory and non-mandatory appendices to the articles; i.e., (1) Scope, roles and responsibilities, (2) Materials, (3) Structural design, (4) Fabrication and installation, (5) Non-destructive examination, (6), Pressure and leak testing, and (7) Terms used in general requirements.
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Electronics and Communications in Japan (Part II: Electronics), 2003
We have developed high power SiC-MESFETs for high-freqeuncy applications. We obtained a cutoff freqeuncy of 9.3 GHz and a maximum oscillation frequency of 34.2 GHz from a 0.5 µm gate MESFET. We measured pulsed output power characteristics of 54.1 W at 1.0 GHz and 11.2 W at 9.4 GHz from a 39.2mm-gate-MESFET and a 9.6mm-gate-width MESFET, respectivly.
Thermomechanical Behavior of Self-recoverable Composite Bonded Magnets and their Magnetic Properties
Journal of the Magnetics Society of Japan, 2010
We previously reported that an advanced preparation method was applied to the synthesis of a radially anisotropic composite bonded magnet with a continuously controlled direction of anisotropy for inner and outer rotor magnets. The preformed magnets were extruded and compressed into ring-shaped magnets by using self-recoverability based on the incomplete three-dimensional (3-D) network molecular structure at an elevated temperature. In this study, an investigation of the thermomechanical behavior of the self-recoverability of the magnets together with their magnetic properties was carried out in order to apply them to small motors as various specific shapes. As a result, the (BH)max of a magnet attained a typical value of 165 kJ/m 3 , and no deterioration of magnetic properties was detected throughout the preparation process even if the magnets were miniaturized at weights ranging from 38 to 400 mg. The reduction in size is attributed to the optimized incomplete 3-D network molecular structure.
Journal of the Japan Society of Applied Electromagnetics and Mechanics, 2021
The purpose of this study is the application of bistable magnetic device (BMD) to magnetic energy harvesting (MEH). This paper presents the new large-diameter BMD for the application to energy harvesting. To improve the BMD output characteristics, multiple twists were applied to the FeCoV wire with a diameter of 1 mm. As a result, it was confirmed that the applying twists reduced the pulse-induced magnetic field and increased the output peak voltage. In addition, the prototype MEH-device using this BMD was able to generate approximately 5 mW of DC power in the magnetic field of 10 mT.