Flux Crystal Growth of Ruddlesden–Popper Titanium Oxysulfides LiLnTiO3S (Ln = La–Gd): Lithium-Ion Mobility in Li1–xNd(Ti1–xNbx)O3S (x = 0–0.25) Hongbo Yuan, Kaori Sugii, Gen Hasegawa, Yu Meng, Yoshitaka Matsushita, Hirofumi Akamatsu, Naoaki Kuwata, Kazunari Yamaura, Yoshihiro Tsujimoto Chemistry of Materials, 2026 We report the flux crystal growth of n = 1 Ruddlesden–Popper type titanium oxysulfides, LiLnTiO3S (Ln = La, Ce, Pr, Nd, Sm, Eu, Gd), using alkali metal halide molten salts. The transparent platelet LiLnTiO3S single crystals were pale yellow or orange, except for dark purple LiCeTiO3S. All LiLnTiO3S members are stable in air, particularly up to 600 °C for Ln = Nd. Single crystal structure analysis revealed that LiLnTiO3S adopted a centrosymmetric tetragonal cell in the space group P4/nmm (no. 129) for Ln = La to Gd, which is in contrast to the corresponding oxide LiLnTiO4, which exhibits a structural symmetry lowering to P-421m for Ln = Sm–Dy via inversion symmetry breaking. The structure of LiLnTiO3S consists of single perovskite layers composed of corner-sharing TiO5S octahedra, with (LiO)2 antifluorite layers and (LnS)2 rock-salt layers stacked above and below along the c-axis. The lithium-ion conductivity of sintered polycrystalline LiNdTiO3S was significantly enhanced by the substitution of Nb5+ for Ti4+, which induced lithium vacancies. When x = 0.20, the bulk ionic conductivity increased from 3.00 × 10–7 S cm–1 at 25 °C to 1.46 × 10–2 S cm–1 at 500 °C, and the activation energy was 0.495 eV, which is lower than those of any other Ruddlesden–Popper type oxide-based solid electrolytes. Anion-directed material design using both oxide and sulfide ions provides opportunities for creating distinct classes of lithium-ion solid electrolytes.
High-pressure synthesis of quantum magnet M-YbTaO4 with a stretched diamond lattice Nicola D. Kelly, Xuan Liang, Siân E. Dutton, Kazunari Yamaura, Yoshihiro Tsujimoto Physical Review Materials, 2026 We report bulk magnetic properties of ytterbium tantalate in its monoclinic fergusonite modification, M − YbTaO 4 . The spin- 1 2 Yb 3 + ions in this phase are arranged on a geometrically frustrated “stretched diamond” lattice. M − YbTaO 4 cannot be prepared at ambient pressure and was instead prepared in a belt-type apparatus at 6 GPa and 1800 ∘ C . Susceptibility and specific heat data show no long-range ordering down to 1.8 K and are consistent with a J eff = 1 2 Kramers doublet which splits in an applied field. Furthermore, under high-pressure synthesis the entire solid solution YbNb x Ta 1 − x O 4 ( 0 ≤ x ≤ 1 ) can be stabilized in the M phase, in contrast to ambient-pressure synthesis which favors the competing M ′ phase for Ta-rich compositions. Subsequent annealing of the Nb-Ta mixed samples resulted in color changes, suggesting oxygen deficiency in some of the as-prepared high pressure samples. There was little variation in the bulk magnetic properties upon varying either the Nb/Ta ratio or the annealing conditions.
Doping-induced variation of anomalous Hall effect in the magnetic Weyl-Kondo metal candidate CeCo1−xFexGe3 Tomomi Furuhashi, Keisuke Hozawa, Yusuke Kozuka, Yoshihiro Tsujimoto, Kazunari Yamaura, Jun Fujioka Physical Review B, 2025 We have investigated the doping-induced variation of magnetic and charge transport properties of single crystalline $\mathrm{Ce}{\mathrm{Co}}_{1\ensuremath{-}x}{\mathrm{Fe}}_{x}{\mathrm{Ge}}_{3}$ with a noncentrosymmetric tetragonal $\mathrm{Ba}\mathrm{Ni}{\mathrm{Sn}}_{3}$-type structure. The magnetization measurements revealed that, with increasing doping level $x$, the antiferromagnetic phase for $x=0$ turns into a ferromagnetic one at $x=0.15$, a cluster-glass-like phase at $x=0.46$, and eventually evolves into a paramagnetic phase above $x=0.67$. For $0\ensuremath{\le}x<0.46$ wherein the electrical resistivity shows the Fermi liquid behavior, the coefficient of the ${T}^{2}$-term of resistivity is small for $0\ensuremath{\le}x\ensuremath{\le}0.33$ but increases sharply at around $x\ensuremath{\sim}0.42$, indicating the enhancement of density of state near the Fermi energy. Hall resistivity measurements indicate that, at 2 K in the ferromagnetic phase, the anomalous Hall conductivity remains nearly constant over the range $0.15\ensuremath{\le}x\ensuremath{\le}0.42$ but markedly decreases with increasing $x$ beyond 0.42. Notably, an anomalous Hall component that is not proportional to magnetization is observed for $x\ensuremath{\ge}0.42$. It is anticipated that the Berry curvature in momentum space significantly changes across the transition from the ferromagnetic phase to cluster-glass-like phase, driven by a change in the Kondo hybridization in the present materials.
Spin fluctuation induced anomalous Hall effect in the distorted kagome antiferromagnet DyAgGe Tomomi Furuhashi, Keita Nagasawa, Yuichi Yamasaki, Hironori Nakao, Yusuke Kozuka, Yoshihiro Tsujimoto, Kazunari Yamaura, Jun Fujioka Physical Review B, 2025 We investigate the magnetic property and charge-transport property for the kagome-frustrated antiferromagnet DyAgGe with the ZrNiAl-type crystal structure by measurements of magnetization, resistivity, and resonant x-ray scattering. The magnetization curve shows the 1/9, 1/3, 5/9, and 7/9 plateaus of saturated magnetization under the magnetic field along the $c$-axis before entering the forced ferromagnetic phase at 7.3 T and 2 K. Magnetic superlattice x-ray reflections with the modulation vector (1/3, 1/3, 0), resonantly enhanced at the Dy ${L}_{3}$ edge, are observed in these plateau phases. All of these phases, except for the 1/9-plateau phase, evolve into the paramagnetic phase around 12 to 15 K with strong competition among them in the field range of 4 to 6 T. Furthermore, we find the large negative magnetoresistivity and anomalous Hall resistivity not proportional to magnetic field or magnetization near and above the magnetic transition temperature around 3-7 T. For comparison, we also investigated the charge-transport for the isostructural magnet DyPtIn, which does not exhibit the field-induced multiple phase transitions. In contrast with the behavior of DyAgGe, DyPtIn does not show remarkable magnetoresistivity and anomalous Hall resistivity near and above the magnetic transition temperature. The anomalous Hall effect persisting above the magnetic transition temperature is likely caused by spin fluctuations enhanced by the competing multiple magnetic phases through the scalar spin chirality mechanism in DyAgGe.
Operando Studies Redirect Spatiotemporal Restructuration of Model Coordinated Oxides in Electrochemical Oxidation Daqin Guan, Hengyue Xu, Yu‐Cheng Huang, Chao Jing, Yoshihiro Tsujimoto, Xiaomin Xu, Zezhou Lin, Jiayi Tang, Zehua Wang, Xiao Sun, Leqi Zhao, Hanwen Liu, Shangheng Liu, Chien‐Te Chen, Chih‐Wen Pao, Meng Ni, Zhiwei Hu, Zongping Shao Advanced Materials, 2025 Tetrahedral, pyramidal, and octahedral metal‐oxygen coordinated ligands are fundamental components in all metal‐oxide structures. Understanding the impacts of their spatiotemporal behaviors during electrochemical oxidation is crucial for diverse applications, yet remains unsolved due to challenges in designing model oxides and conducting operando characterizations. Herein, combining a suite of advanced operando characterizations and systematic computations, a link between oxygen‐evolving performance and operational structural properties is established on model oxides. Compared with tetrahedral and octahedral structures, pyramidal structure is more susceptible to OH− attack due to its pristine unsaturated and asymmetric features and constant single‐electron occupancy on the active z2 orbital during reaction, leading to surface‐to‐bulk restructuration into active amorphous high‐valence CoOOHx with edge‐sharing configurations. This is accompanied by ion leaching to create nanoscale space, following a leaching tendency of Sr2+ > Ba2+ > La3+ > Y3+. Operando soft X‐ray absorption spectroscopy demonstrates a harder non‐uniform dehydrogenation process over time (Co3+OOH → Co3+/4+OOHx → Co4+OO) because of the enhanced CoO covalency with higher energy barriers. Lattice oxygen participates in active CoOOHx formation but sacrifices stability. To address this activity‐stability trade‐off, an ion‐tuning strategy is proposed to simultaneously enhance both activity and stability in electrode and device.
Large anomalous Hall effect in spin fluctuating devil’s staircase Naoki Abe, Yuya Hano, Hiroaki Ishizuka, Yusuke Kozuka, Terumasa Tadano, Yoshihiro Tsujimoto, Kazunari Yamaura, Shintaro Ishiwata, Jun Fujioka Npj Quantum Materials, 2024 Electrons in metals can show a giant anomalous Hall effect (AHE) when interacting with characteristic spin texture. The AHE has been discussed in terms of scalar-spin-chirality (SSC) in long-range-ordered noncollinear spin textures typified by Skyrmion. The SSC becomes effective even in the paramagnetic state with thermal fluctuations, but the resultant AHE has been limited to be very small. Here, we report the observation of large AHE caused by the spin fluctuation near the devil’s staircase transition in a collinear antiferromagnetic metal SrCo6O11. The AHE is prominent near and above the transition temperature at moderate magnetic fields, where the anomalous Hall angle becomes the highest level among known oxide collinear ferromagnets/antiferromagnets (>2%). Furthermore, the anomalous Hall conductivity is quadratically scaled to the conductivity. These results imply that the thermally induced solitonic spin defects inherent to the devil’s staircase transition promote SSC-induced skew scattering.
Magnetically induced metal-insulator transition in Pb2CaOsO6 Henrik Jacobsen, Hai L. Feng, Andrew J. Princep, Marein C. Rahn, Yanfeng Guo, Jie Chen, Yoshitaka Matsushita, Yoshihiro Tsujimoto, Masahiro Nagao, Dmitry Khalyavin, Pascal Manuel, Claire A. Murray, Christian Donnerer, James G. Vale, Marco Moretti Sala, Kazunari Yamaura, Andrew T. Boothroyd Physical Review B, 2020
Enhanced magnetization of the highest- TC ferrimagnetic oxide Sr2CrOs O6 Jie Chen, Xiao Wang, Zhiwei Hu, Liu Hao Tjeng, Stefano Agrestini, Manuel Valvidares, Kai Chen, Lucie Nataf, Francois Baudelet, Masahiro Nagao, Yoshiyuki Inaguma, Alexei A. Belik, Yoshihiro Tsujimoto, Yoshitaka Matsushita, Taras Kolodiazhnyi, Raimundas Sereika, Masahiko Tanaka, Kazunari Yamaura Physical Review B, 2020
Strongly gapped spin-wave excitation in the insulating phase of NaOsO3 S. Calder, J. G. Vale, N. Bogdanov, C. Donnerer, D. Pincini, M. Moretti Sala, X. Liu, M. H. Upton, D. Casa, Y. G. Shi, Y. Tsujimoto, K. Yamaura, J. P. Hill, J. van den Brink, D. F. McMorrow, A. D. Christianson Physical Review B, 2017
Enhanced spin-phonon-electronic coupling in a 5d oxide S. Calder, J. H. Lee, M. B. Stone, M. D. Lumsden, J. C. Lang, M. Feygenson, Z. Zhao, J.-Q. Yan, Y. G. Shi, Y. S. Sun, Y. Tsujimoto, K. Yamaura, A. D. Christianson Nature Communications, 2015
High-pressure synthesis, crystal structure and magnetic properties of TlCrO3 perovskite Wei Yi, Yoshitaka Matsushita, Yoshio Katsuya, Kazunari Yamaura, Yoshihiro Tsujimoto, Igor A. Presniakov, Alexey V. Sobolev, Yana S. Glazkova, Yuliya O. Lekina, Naohito Tsujii, Shigeki Nimori, Kanji Takehana, Yasutaka Imanaka, Alexei A. Belik Dalton Transactions, 2015
Magnetically driven metal-insulator transition in NaOsO 3 S. Calder, V. O. Garlea, D. F. McMorrow, M. D. Lumsden, M. B. Stone, J. C. Lang, J.-W. Kim, J. A. Schlueter, Y. G. Shi, K. Yamaura, Y. S. Sun, Y. Tsujimoto, A. D. Christianson Physical Review Letters, 2012
Quadruple-layered perovskite (CuCl)Ca 2NaNb 4O 13 A. Kitada, Y. Tsujimoto, T. Yamamoto, Y. Kobayashi, Y. Narumi, K. Kindo, A.A. Aczel, G.M. Luke, Y.J. Uemura, Y. Kiuchi, Y. Ueda, K. Yoshimura, Y. Ajiro, H. Kageyama Journal of Solid State Chemistry, 2012
Magnetic excitations in infinite-layer antiferromagnetic insulator Keisuke Tomiyasu, Hiroshi Kageyama, Changhoon Lee, Mike H. Whangbo, Yoshihiro Tsujimoto, Kazuyoshi Yoshimura, Jon W. Taylor, Anna Llobet, Frans Trouw, Kazuhisa Kakurai, Kazuyoshi Yamada Journal of the Physical Society of Japan, 2010
Quantum phase transition in (CuCl) la (Nb1-x Tax) 2 O7 A. Kitada, Y. Tsujimoto, H. Kageyama, Y. Ajiro, M. Nishi, Y. Narumi, K. Kindo, M. Ichihara, Y. Ueda, Y. J. Uemura, K. Yoshimura Physical Review B Condensed Matter and Materials Physics, 2009
Spin transition in a four-coordinate iron oxide T. Kawakami, Y. Tsujimoto, H. Kageyama, Xing-Qiu Chen, C. L. Fu, C. Tassel, A. Kitada, S. Suto, K. Hirama, Y. Sekiya, Y. Makino, T. Okada, T. Yagi, N. Hayashi, K. Yoshimura, S. Nasu, R. Podloucky, M. Takano Nature Chemistry, 2009
CaFeO2: A new type of layered structure with iron in a distorted square planar coordination Cédric Tassel, José Miguel Pruneda, Naoaki Hayashi, Takashi Watanabe, Atsushi Kitada, Yoshihiro Tsujimoto, Hiroshi Kageyama, Kazuyoshi Yoshimura, Mikio Takano, Masakazu Nishi, Kenji Ohoyama, Masaichiro Mizumaki, Naomi Kawamura, Jorge Íñiguez, Enric Canadell Journal of the American Chemical Society, 2009
