Gyro-spintronic material science using vorticity gradient in solids

Nozaki, Yukio*; Sukegawa, Hiroaki*; Watanabe, Shinichi*; Yunoki, Seiji*; Horaguchi, Taisuke*; Nakayama, Hayato*; Yamanoi, Kazuto*; Wen, Z.*; He, C.*; Song, J.*; et al.

Science and Technology of Advanced Materials, 26(1), p.2428153_1 - 2428153_39, 2025/02

https://doi.org/10.1080/14686996.2024.2428153

Highly accurate evaluation of spin-torque efficiency by measuring in-plane angular dependence of spin-torque ferromagnetic resonance

Horaguchi, Taisuke*; Matsuo, Mamoru; Nozaki, Yukio*

Journal of Magnetism and Magnetic Materials, 505, p.166727_1 - 166727_5, 2020/07

https://doi.org/10.1016/j.jmmm.2020.166727

Chemical misfit origin of solute strengthening in iron alloys

Wakeda, Masato*; Tsuru, Tomohito; Koyama, Masanori*; Ozaki, Taisuke*; Sawada, Hideaki*; Itakura, Mitsuhiro; Ogata, Shigenobu*

Acta Materialia, 131, p.445 - 456, 2017/06

https://doi.org/10.1016/j.actamat.2017.04.017

Most of the solute species show a significant interaction with the dislocation core, while only several solute species among them, such as Si, P, and Cu, significantly lower the Peierls potential of the screw dislocation motion. A first-principles interaction energy with the "Easy-core" structure excellently correlates with the change in the -surface caused by solute atoms (i.e., chemical misfit). We show the availability of the interaction energy to predict the effect of each species on macroscopic critical resolved shear stress (CRSS) of the dilute Fe alloy. The CRSS at low and high temperature for various alloys basically agree with experiment CRSS. These results provide a novel understanding of the interaction between a screw dislocation and solute species from the first-principles.

Progress in R&D efforts on the energy recovery linac in Japan

Sakanaka, Shogo*; Ago, Tomonori*; Enomoto, Atsushi*; Fukuda, Shigeki*; Furukawa, Kazuro*; Furuya, Takaaki*; Haga, Kaiichi*; Harada, Kentaro*; Hiramatsu, Shigenori*; Honda, Toru*; et al.

Proceedings of 11th European Particle Accelerator Conference (EPAC '08) (CD-ROM), p.205 - 207, 2008/06

Future synchrotron light sources based on the energy-recovery linacs (ERLs) are expected to be capable of producing super-brilliant and/or ultra-short pulses of synchrotron radiation. Our Japanese collaboration team is making efforts for realizing an ERL-based hard X-ray source. We report recent progress in our R&D efforts.

GPU acceleration of first-principles electronic structure calculation software OpenMX and its application to modified-DNA

Kawai, Hiroyuki*; Sekikawa, Takuya; Ozaki, Taisuke*; Furuya, Shinnosuke*; Ono, Yoshiaki*

no journal, , 

First-principles electronic structure calculation software OpenMX is a calculation code based on density functional theory, and is mainly used to obtain the most stable structures and electronic states of materials. In this study, we attempted to develop a method to accelerate OpenMX calculations using a GPU (Graphics Processing Unit), which is usually used for image processing, and succeeded in reducing the calculation time to about one-half of that using the same number of CPUs in a benchmark calculation on DNA. The benchmark calculation on DNA succeeded in reducing the calculation time by about one-half compared to the same number of CPUs. We then applied the method developed in this study to modified-DNA (DNA in which some of the atoms constituting a base pair are replaced with transition metals or organic molecules), which has been investigated using OpenMX, and verified the degree of speed-up. Details of the obtained modified-DNA, including its electronic state, will be presented on the day.

Development and accuracy evaluation of core-excited pseudopotentials using large-scale data

Kawai, Hiroyuki*; An, S.*; Ozaki, Taisuke*; Sekikawa, Takuya; Ono, Yoshiaki*

no journal, , 

X-ray photoemission spectroscopy (XPS) is one of the most widely used techniques to study the chemical composition and electronic structure of materials near the surface. The physical quantity measured by XPS is essentially the energy value of the core electrons. On the other hand, theoretical calculations of the core-electron energy require the pseudopotential, which is the interaction energy between the excited core electrons and the surrounding nuclei and other electrons (core-excitation pseudopotential). In this study, we optimized many parameters necessary to obtain the core-excitation pseudopotential for Se using a Monte Carlo method, and produced a high-precision core-excitation pseudopotential for Se. Using this core-excitation pseudopotential, we calculated core-electron energy values for four Se compounds and found that they reproduced XPS measurements with high accuracy. The results of this study are expected to become a standard for theoretical calculations of XPS measurements in the future.