Yoshiharu Kanegae

Stability of π-Phase in Atomic-Scale Superconductor/Magnet Multilayered System

Atomic-scale superconductor/ferromagnet (S/F) and superconductor/antiferromagnet (S/AF) multilayered systems are investigated in order to clarify the stability of the π-phase where the phase differ...

Nuclear Magnetic Resonance in Atomic-Scale Superconductor/Magnet Multilayered Systems

We investigate the nuclear spin–lattice relaxation rate ( T 1 T ) -1 in atomic-scale superconductor/magnet multilayered systems and discuss the discrepancy between two recent ( T 1 T ) -1 experiments on Ru in RuSr 2 YCu 2 O 8 . When the magnetic layers are in the antiferromagnetic state, ( T 1 T ) -1 in the magnetic layers is shown to decrease with decreasing temperature due to the excitation gap associated with the magnetic ordering. The proximity effect of superconductivity on ( T 1 T ) -1 in the magnetic layer is negligibly small. Our result indicates that the temperature dependence of ( T 1 T ) -1 on Ru in RuSr 2 YCu 2 O 8 likely originates from the antiferromagnetism in the RuO 2 layers, but not from the superconductivity in the CuO 2 layers.

Strain Optimization to Reduce Gate Leakage Current in MOS Transistors with Silicon Oxynitride Gate Dielectrics by Use of First-Principles Calculations

We developed a method for optimizing strain to reduce gate leakage current in metal-oxide-semiconductor (MOS) transistors by using first-principles calculations. This method was used to investigate the possibility of decreasing gate leakage current by controlling the strain on gate dielectric materials. We found that compressive strain decreases drastically the leakage current through silicon oxynitride (SiON) gate dielectrics. This change retlects strain-induced change in the band gap of the material. Using finite element analysis to estimate the strain in MOS transistors, we showed the usability of SiON in terms of gate leakage currents and the importance of controlling the strain on the gate dielectric materials.

Monte Carlo Study on the Nuclear Magnetic Ordering in Scandium Crystal: Possibility of a Ferrimagnetic State

Nuclear magnetic ordering is investigated in scandium crystal by the Monte Carlo simulation. We determine the phase diagram in the ground state with respect to interactions between the nuclear spins. In this phase diagram, we find a ferrimagnetic state with the total magnetization being smaller than the complete ferromagnetism by 1/3: This state changes into the ferromagnetism at a finite external magnetic field, which leads to a threefold jump in the magnetization as was observed by the experiment. Thus, this state is a strong candidate for the nuclear magnetic ordering in scandium below \(T\lesssim 2[\mu{\rm K}]\).