Recently, wide-bandgap (WBG) power semiconductors made of silicon carbide (SiC) and gallium nitride (GaN) have been widely developed as high-speed switching devises. Many researchers have studied novel magnetic materials, such as nanocrystalline magnetic materials (NMMs), for low-loss electric motors and transformers. This study experimentally examines the hysteresis (B–H) curve and iron loss properties of the NMM core excited using a pulse width modulation (PWM) inverter at high carrier frequencies on the order of MHz with and without the dead time. For comparison, the magnetic properties of amorphous magnetic materials (AMMs) core are also evaluated. Particularly at high carrier frequencies (approximately 1 MHz), the iron loss of NMM and AMM cores significantly depends on the dead time. Compared with the case of the AMM core, the NMM core suppresses the increasing rate of iron losses caused by the dead time because the area of minor loops in NMM becomes small, particularly in high-frequency regions.

  We numerically investigated the refraction property of spin waves (SWs) at thickness step in films with out-of-plane magnetization, in which the SWs propagate isotropically in the film plane. It was confirmed the isotropic SWs were refracted at a thickness step by following the Snell's law. We also found that the refraction angle of SWs of the dipole-exchange mode depends on the resonant frequency, indicating that the chromatic aberration effect should be taken into account in designing magnonic devices.

  The giant spin Hall effect (SHE) in topological insulators (TIs) is very attractive for applications to various spintronic devices, notably spin-orbit torque magnetoresistive random-access memory (SOT-MRAM). In this paper, we review the recent progress on the giant SHE in TIs, with emphasis on the role of topological surface states. We discuss current challenges and future prospects for TIs as a realistic material in SOT-MRAM.