arXiv subjects

Seiji Sakai

Publications and source records attributed to Seiji Sakai.

3 recordsLinked to original sources

arXiv2025

X-ray detected ferromagnetic resonance spectrometer with an out-of-vacuum photodetector

X-ray detected ferromagnetic resonance (XFMR) spectroscopy is an experimental technique for element-specific spin dynamics in the GHz regime and has been utilized to study spintronic materials. The XFMR signal is usually obtained by detecting X-ray excited optical luminescence (XEOL) emitted from a sample substrate. Here, we report the development of an XFMR spectrometer that is designed to place a photodetector for XEOL detection outside an ultra-high-vacuum chamber. This configuration allows for the easy replacement of detectors, such as photodiodes, CCD cameras, and spectrometers, depending on the experimental requirements. We demonstrated the measurement of XEOL spectra from MgO using a visible light spectrometer as well as the detection of XFMR signals originating from the spin precession of a permalloy (Ni80Fe20) thin film using a photodiode detector. The XFMR spectrometer with an out-of-vacuum photodetector expands possibilities for advanced measurements such as XFMR microscopy.

cond-mat.mtrl-sci↗

arXiv2021

Perpendicular magnetic anisotropy at Fe/Au(111) interface studied by Mössbauer, x-ray absorption, and photoemission spectroscopies

The origin of the interfacial perpendicular magnetic anisotropy (PMA) induced in the ultrathin Fe layer on the Au(111) surface was examined using synchrotron-radiation-based Mössbauer spectroscopy (MS), X-ray magnetic circular dichroism (XMCD), and angle-resolved photoemission spectroscopy (ARPES). To probe the detailed interfacial electronic structure of orbital hybridization between the Fe 3$d$ and Au 6$p$ bands, we detected the interfacial proximity effect, which modulates the valence-band electronic structure of Fe, resulting in PMA. MS and XMCD measurements were used to detect the interfacial magnetic structure and anisotropy in orbital magnetic moments, respectively. $In$-$situ$ ARPES also confirms the initial growth of Fe on large spin-orbit coupled surface Shockley states under Au(111) modulated electronic states in the vicinity of the Fermi level. This suggests that PMA in the Fe/Au(111) interface originates from the cooperation effects among the spin, orbital magnetic moments in Fe, and large spin-orbit coupling in Au. These findings pave the way to develop interfacial PMA using $p$-$d$ hybridization with a large spin-orbit interaction.

cond-mat.mtrl-sci↗

arXiv2013

The high hydrogen adsorption rate material based on graphane decorated with alkali metals

The graphane with chemically bonded alkali metals (Li, Na, K) was considered as potential material for hydrogen storage. The ab initio calculations show that such material can adsorb as many as 4 hydrogen molecules per Li, Na and K metal atoms. These values correspond to 12.20 wt%, 10.33 wt% and 8.56 wt% of hydrogen, respectively and exceed the DOE requirements. The thermodynamic analysis shows that Li-graphane complex is the most promising for hydrogen storage with ability to adsorb 3 hydrogen molecules per metal atom at 300 K and pressure in the range from 5 to 250 atm.

cond-mat.mes-hall↗