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= 
one-dimensional Ising-like antiferromagnet BaCo
VO
木村 尚次郎*; 大西 弘明; 奥谷 顕*; 赤木 暢*; 鳴海 康雄*; 萩原 政幸*; 奥西 巧一*; 金道 浩一*; He, Z.*; 谷山 智康*; et al.
Physical Review B, 105(1), p.014417_1 - 014417_9, 2022/01
被引用回数：3 パーセンタイル：45.85(Materials Science, Multidisciplinary)In this study, we clarify the selection rules of optical transitions from the ground state to the magnetic excited states in the quasi-one-dimensional quantum Ising-like antiferromagnet BaCoVO with spin = using the high-field electron spin resonance measurement with illuminating polarized electromagnetic waves. We demonstrate that the unconventional magnetic excitation via the pair creation of quasipaticles at wave numbers 
and 
in the field-induced quantum critical state can couple with both oscillating magnetic and electric fields. Our density matrix renormalization group calculations indicate that the observed selection rules can be explained by two- and four-fold periodical spin interactions, originating from the screw chain structure in BaCoVO, in addition to the magnetoelectric coupling between spins and electric dipoles.
友田 陽*; Wang, Y.*; 大村 孝仁*; 関戸 信彰*; Harjo, S.; 川崎 卓郎; Gong, W.*; 谷山 明*
鉄と鋼, 106(5), p.262 - 271, 2020/05
被引用回数：0 パーセンタイル：0(Metallurgy & Metallurgical Engineering)The phase transformation behavior from austenite upon cooling in a 1.5Mn-1.5Si-0.2C steel was 
monitored using dilatometry, X-ray and neutron diffractions. The starting temperature of ferrite transformation was in good agreement between dilatometry and neutron diffraction, whereas much higher in X-ray diffraction. Such a discrepancy in transformation temperature is attributed to the change in chemical composition near the surface of a specimen heated to elevated temperatures in a helium gas atmosphere for X-ray diffraction. 
neutron diffraction enables us to investigate the changes in lattice constants of ferrite and austenite, which are affected by not only thermal contraction but also transformation strains, thermal misfit strains and carbon enrichment in austenite. Pearlite transformation started after carbon enrichment in austenite reached approximately 0.7 mass% and contributed to diffraction line broadening.
友田 陽*; 関戸 信彰*; 徐 平光; 川崎 卓郎; Harjo, S.; 田中 雅彦*; 篠原 武尚; Su, Y. H.; 谷山 明*
鉄と鋼, 103(10), p.570 - 578, 2017/10
被引用回数：13 パーセンタイル：50.55(Metallurgy & Metallurgical Engineering)Various methods were employed to measure the austenite volume fraction in a 1.5Mn-1.5Si-0.2C steel. It has been confirmed that the volume fractions determined by transmission electron microscopy, scanning electron microscopy/electron back scatter diffraction, X-ray diffraction and neutron diffraction exhibit a general trend to become larger in this order, although the values obtained by X-ray and neutron diffraction are similar in the present steel because austenite is relatively stable. The austenite volume fractions determined by diffraction methods have been found to be affected by the measuring specimen direction, i.e., texture, even by applying the conventional correcting procedure. To avoid this influence, it is recommended to measure both of volume fraction and texture simultaneously using neutron diffraction. Although synchrotron X-ray shows higher angle resolution, its small incident beam size brings poor statistic reliability. The influence of texture cannot be avoided for transmission Bragg edge measurement, either, which must be overcome to realize 2D or 3D volume fraction mapping.
