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.
Operando Studies Redirect Spatiotemporal Restructuration of Model Coordinated Oxides in Electrochemical Oxidation Daqin Guan, Hengyue Xu, Yu‐Cheng Huang, Chao Jing, Yoshihiro Tsujimoto, et al. 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, et al. 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.
