In this paper, we focus on an evaluation of core losses in permanent magnet synchronous motors (PMSMs) made of nanocrystalline magnetic materials under inverter and sinusoidal excitations. To discuss the core loss properties of a nanocrystalline motor, comparison with PMSMs made of amorphous magnetic materials and non-oriented (NO) silicon steel sheets is also performed. Under sinusoidal excitation, the core losses of the nanocrystalline motor were about 0.7 and 0.5 times smaller than those of the amorphous and NO motors, respectively. In particular, we found that the nanocrystalline motor reduced the core loss on the basis of time harmonic components in comparison with not only the NO motor but also the amorphous motor. On the basis of our results, the nanocrystalline motor is expected to be suitable for use in high-speed and high-frequency regions.

  We experimentally and numerically examined the magnetic properties of magnetic materials under room- and high-temperature inverter excitations. We show that the iron loss and hysteresis properties of magnetic materials under pulse width modulation (PWM) inverter excitation depend strongly on the temperature dependence of semiconductor characteristics. The iron loss under PWM inverter excitation decreased as the temperatures of semiconductors (Si-insulated gate bipolar transistors and Si-diodes) increased. In addition, it was found that the rate of change of iron loss based on the temperature dependence of semiconductor characteristics at a high carrier frequency was larger than that at a low carrier frequency.

  Fe_100–xCo_x (x = 0, 30, 50 at. %) alloy thin films are prepared on MgO substrates of (001), (110), and (111) orientations by ultra-high vacuum magnetron sputtering. The influences of film orientation and composition on the magnetic anisotropy and the magnetostriction are investigated. Fe_100–xCo_x(001) single-crystal and (211) bi-crystal films are respectively obtained on MgO(001) and (110) substrates. Fe_100–xCo_x(110) films are epitaxially grown on MgO(111) substrates with two types of variants with the crystallographic orientation relationships similar to Nishiyama-Wasserman and Kurdjumov-Sachs. The (001) single-crystal and the (211) bi-crystal films, respectively, show four- and two-fold symmetric in-plane magnetic anisotropies, which are reflecting the magnetocrystalline anisotropy of Fe_100–xCo_x crystal with the easy magnetization axes parallel to <100> or <111>. On the contrary, isotropic in-plane magnetization properties are observed for the (110) films due to an influence of the variant structure. The magnetostriction is measured under rotating magnetic field by using a cantilever method. As the Co content increases from 0 to 50 at. %, the magnetostriction coefficients, λ₁₀₀ and λ₁₁₁, respectively increase from +10^–5 to +10^–4 and from –10^–5 to +10^–5 for both Fe_100–xCo_x(001) single-crystal and (211) bi-crystal films. Large λ₁₀₀ values are also indicated for the Fe_100–xCo_x(110) epitaxial films (x = 30, 50). The present study shows that it is possible to obtain large magnetostriction of 10^–4 by control of the film orientation and composition.

  SiO₂CuFe₂O₄ nanoparticles encapsulated by different amounts of amorphous SiO₂ were prepared by a wet chemical method. These nanoparticles were characterized by X-ray diffraction and X-ray absorption fine structure analysis and found to have either a tetragonal or a cubic structure depending on the amount of SiO₂. Magnetization measurements were performed for all samples using a SQUID magnetometer. The tetragonal nanoparticles showed a smaller maximum magnetization (M_S) and a larger coercive force (H_C) than the cubic nanoparticles.

  In this paper, the development of a CMOS switch buck DC-DC converter fabricated in an organic interposer with an embedded power inductor is described. The power inductor is fabricated by using a magnetic core made of an Fe-based amorphous alloy powder-filler/epoxy composite sheet to form a fully closed magnetic circuit and is embedded in the organic interposer in a lamination process. The fabricated power inductor is located under a CMOS control chip and has a of 3.5-mm-square footprint. The CMOS switch buck DC-DC converter runs at 20 MHz, and the fabricated power inductor has an inductance of 150 nH and Q-factor of 38 at around 20 MHz. Furthermore, the influence of magnetic flux leakage from the embedded power inductor to a copper wiring pattern on the surface was analyzed in a simulation that utilized three-dimensional electromagnetic field analysis software (ANSYS; HFSS). Based on the simulation result, the conduction losses of the inductor were calculated under the assumption of use in a synchronous buck converter operating with a 5-V input and 3.3-V 0.8-A output.