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We report on current-induced magnetization switching in a nanomagnet with perpendicular anisotropy, and investigate the effects of the damping constant (α) on the switching current (Isw) by varying the nanosecond-scale pulse current duration (tp), the saturation magnetization (Ms), and the magnetocrystalline anisotropy (Ku). The results show that reduction of α below a certain threshold (αc) is ineffective in reducing Isw for short tp. When tp is short, it is necessary to reduce both α and Ms simultaneously until αc is reached to reduce Isw. The results presented here offer a promising route for the design of ultrafast information storage and logic devices using current-induced magnetization switching.

We study spontaneous emission control in a buried-heterostructure (BH) photonic crystal (PhC) cavity in which InGaAsP quantum wells (QWs) are embedded in an InP PhC. Spontaneous emission from QW-PhC cavities have been extensively investigated, but they suffer from poor carrier confinement and surface non-radiative recombination. Therefore, the clear spontaneous emission control has been only observed in quantum dots PhC cavities. The present study shows that the BH-QW-PhC cavities can exhibit distinctive spontaneous emission control in QW-PhCs. We observed large emission-rate ratio between the on- and off-resonant conditions of 30:1. This is the highest ratio reported for QW-PhCs.

A single vortex-core switching induced by current injection into a ferromagnetic disk is detected in real time using a three-terminal device with the tunneling magnetoresistance junction. The real time observation reveals that the electrical core switching is completed within a few 100 ps. It is also found that the core switching takes place at the specific positions inside the disk.

A single vortex-core switching in a ferromagnetic disk is detected in real time by using a three-terminal device with the tunneling magnetoresistance junction. We show that the device works as a vortex core memory cell, where reading and writing can be done in an all-electrical way: binary data corresponding to the core direction can be read out electrically as the amplitude of the output, while the data can be written electrically by applying a pulsed current.