Graduate School of Engineering
Department of Materials Science

Nano-materials Science
Materials Quantum Science (Prof. Nitta)

Research Topics

Semiconductor Spintronics

Semiconductor and ferromagnetic materials are indispensable for present electronics technologies. Ferromagnetic metals show a magnetization hysteresis loop in which the cooperative motion of large number of electron spins plays a role. In semiconductor electronics, electron charge playas the key role while electron spin plays no role at all. Electronics based on the spin degrees of freedom of the electron represents a new paradigm, which will require a way of controlling electron spins in semiconductor channels by using the gate voltage.

We have experimentally confirmed that the spin-orbit interaction in a semiconductor two-dimensional electron gas channel can be controlled by gate electric fields. To realize spin functional devices, we are studying on spin injection into semiconductor channel and electrical manipulation of spins in semiconductors.

Magnetic refrigerants for magnetic refrigeration

By changing magnetic filed, magnetic materials exhibit caloric changes such as heat absorption and decrease of temperature. These phenomena are called the magnetocaloric effects (MCEs), being related to the magnetic entropy change. Magnetic refrigerations have no relation with chlorofluorocarbon (CFC). In addition, their efficiency is higher than that of the vapor compression refrigeration of CFC.

Recently, we have demonstrated that La(FexSi1-x)13 compounds exhibit large MCEs around the Curie temperature due to the field-induced first-order transition from the paramagnetic to the ferromagnetic state, that is, itinerant-electron metamagnetic transition. We are focusing on the research and developments for applications of the MCEs in La(FexSi1-x)13-based compounds for applications to high performance magnetic refrigerants working in a wide temperature range covering room temperature.