Since the pulse width of ultra-short terahertz pulsed light is as short as picoseconds (1/1 trillion seconds), when a ferromagnet is irradiated, the magnetization responds to the pulse waveform with little effect of magnetic friction. It is known that it is modulated at high speed.By applying this, it is expected that the magnetization can be reversed at a very high speed at the picosecond level, and a memory device with an operating speed about 1000 times faster than the current one can be realized. In the study, the magnitude of the magnetization modulation was less than about 1% of the saturation magnetization.

　In previous research, the research group revealed that using a special semiconductor-based ferromagnetic material, not only the magnetic field component of light but also the electric field component can greatly contribute to magnetization modulation.From here, we decided to use a sample in which ferromagnetic nanoparticles are embedded in a semiconductor, and when we observed the change in magnetization when the sample was irradiated with ultra-short terahertz pulse light, the amount of magnetization modulation was 20% of the saturation magnetization. In addition, it is said that a large magnetization modulation that is more than 20 times that of the conventional research has been realized.

　Memory devices in today's highly information-oriented society are composed of semiconductors, but most of them are volatile, so data is lost when the power is turned off.On the other hand, since the magnetization of a ferromagnet is non-volatile, it is possible to realize a memory device in which data is not erased even when the power is turned off by storing information using the direction of magnetization.

　This result is expected to lead to the realization of an ultrafast non-volatile memory that utilizes magnetization reversal in picoseconds.

Paper information:[Applied Physics Letters] Large terahertz magnetization response in ferromagnets nanoparticles