Non-metallic materials, such as inorganic/organic semiconductors and topological quantum materials are now collecting significant attention in modern spintronics. The progress of the research field using the materials is quite rapid and tremendous amounts of significant studies have been published. In this review article, some important milestone works are introduced to enhance further acceleration of the research fields.
Ferrite thin film magnetic core integrated radio frequency inductors (RFIs) were investigated in order to realize RFIs with a smaller size, higher driving frequency, and higher quality factor (Q). The ferrite thin films were fabricated by low-temperature spin-spray deposition assuming adaptation to the photolithography process for inductor fabrication with two different compositions: Ni0.16Zn0.20Fe2.64O4+δ (NZFO) and Co0.11Fe2.89O4+δ (CFO). The RFI with CFO had a 34% higher inductance and 43% Q improvement compared with the air core RFI at a frequency of 1 GHz. It was confirmed that the complex permeability of the films was correlated with the frequency characteristics of the RFIs with the ferrite thin films. The results suggest that integrating ferrite thin film in RFIs is effective for future mobile device applications.
It is essential to establish a simple and practical method for quantitatively estimating the iron loss considering the dynamic hysteresis behavior to further improve the efficiency of electric machines. In a previous study, a novel simple magnetic circuit model representing the dynamic hysteresis characteristics was presented by incorporating a play model, one of the phenomenological dc hysteresis models, and a Cauer circuit, which can consider the skin effect. It was demonstrated that this magnetic circuit model could accurately calculate the hysteresis loops and iron loss even under PMW excitation for magnetic reactors made of several types of core materials in a short time. However, this method can only be used for an object with a simple shape, such as a ring core. Hence, this paper describes that the previously proposed magnetic circuit model is extended to a reluctance network analysis (RNA) to expand the application range. Furthermore, the proposed method was experimentally validated using an interior permanent magnet (IPM) synchronous motor driven by a PWM converter as the examination target.
Magnetic Moment Method (MMM) is well known for its ”lightweight” and simplicity of implementation; however, meshing must be carefully treated to obtain accurate results. In this paper, the MMM with the idea of the Magnetic Surface Charge method is proposed that is free from the meshing problem. Accelerator magnets; a C-shaped dipole and a quadrupole magnet, are analyzed, and it is shown that the proposed method outperforms currently available finite-element packages with respect to the CPU time and accuracy of the magnetic field.