Suppression of a Structural Phase Transition by an Orientational Disorder of Counteranions in an Organic Conductor, β″-β″-(BEDT-TTF)ClCHSO.

In 2022, we reported that the β″-(BEDT-TTF)ClCHSO salt () has a phase transition at 210 K on cooling and 260 K on heating, which was suggested as a nondoped-to-doped transition. During the synthesis of , a second salt was coproduced, the structure and properties of which are reported here. The new salt β″-β″-(BEDT-TTF)ClCHSO () has the same composition and is isomorphous to , the low-temperature phase of .

High-temperature magnetic anomaly via suppression of antisite disorder through synthesis route modification in a Kitaev candidate CuIrO.

By incorporating inert KCl into the NaIrO+ 2CuCl → CuIrO+ 2NaCl topochemical reaction, we significantly reduced the synthesis temperature of CuIrOfrom the 350 °C reported in previous studies to 170 °C. This adjustment decreased the Cu/Ir antisite disorder concentration in CuIrOfrom ∼19% to ∼5%. Furthermore, magnetic susceptibility measurements of the present CuIrOsample revealed a weak ferromagnetic-like anomaly with hysteresis at a magnetic transition temperature of ∼70 K.

J_{eff}=1/2 Hyperoctagon Lattice in Cobalt Oxalate Metal-Organic Framework.

We report the magnetic properties of a cobalt oxalate metal-organic framework featuring the hyperoctagon lattice. Our thermodynamic measurements reveal the J_{eff}=1/2 state of the high-spin Co^{2+} (3d^{7}) ion and the two successive magnetic transitions at zero field with two-stage entropy release. ^{13}C-NMR measurements reveal the absence of an internal magnetic field in the intermediate temperature phase.

Quantum Liquid States of Spin Solitons in a Ferroelectric Spin-Peierls State.

In this study, we performed high-magnetic-field magnetization, dielectric, and ultrasound measurements on an organic salt showing a ferroelectric spin-Peierls (FSP) state, which is in close proximity to a quantum critical point. In contrast to the sparsely distributed gaslike spin solitons typically observed in conventional spin-Peierls (SP) states, the FSP state exhibits dense liquidlike spin solitons resulting from strong quantum fluctuations, even at low fields. Nevertheless, akin to conventional SP systems, a magnetic-field-induced transition is observed in the FSP state.

Piston-cylinder cell made of Ni-Cr-Al alloy for magnetic susceptibility measurements under high pressures in pulsed high magnetic fields.

We developed a metallic pressure cell made of 56Ni-40Cr-4Al (Ni-Cr-Al) alloy for use with a non-destructive pulse magnet and a magnetic susceptibility measurement apparatus with a proximity detector oscillator (PDO) in pulsed magnetic fields of up to 51 T under pressures of up to 2.1 GPa. Both the sample and sensor coil of the PDO were placed in the cell so that the magnetic signal from Ni-Cr-Al would not overlay the intrinsic magnetic susceptibility of the sample.

Possible intermediate quantum spin liquid phase in α-RuCl under high magnetic fields up to 100 T.

Pursuing the exotic quantum spin liquid (QSL) state in the Kitaev material α-RuCl has intrigued great research interest recently. A fascinating question is on the possible existence of a field-induced QSL phase in this compound. Here we perform high-field magnetization measurements of α-RuCl up to 102 T employing the non-destructive and destructive pulsed magnets.

Signatures of a magnetic superstructure phase induced by ultrahigh magnetic fields in a breathing pyrochlore antiferromagnet.

The mutual coupling of spin and lattice degrees of freedom is ubiquitous in magnetic materials and potentially creates exotic magnetic states in response to the external magnetic field. Particularly, geometrically frustrated magnets serve as a fertile playground for realizing magnetic superstructure phases. Here, we observe an unconventional two-step magnetostructural transition prior to a half-magnetization plateau in a breathing pyrochlore chromium spinel by means of state-of-the-art magnetization and magnetostriction measurements in ultrahigh magnetic fields available up to 600 T.

Expanded quantum vortex liquid regimes in the electron nematic superconductors FeSeS and FeSeTe.

The quantum vortex liquid (QVL) is an intriguing state of type-II superconductors in which intense quantum fluctuations of the superconducting (SC) order parameter destroy the Abrikosov lattice even at very low temperatures. Such a state has only rarely been observed, however, and remains poorly understood. One of the key questions is the precise origin of such intense quantum fluctuations and the role of nearby non-SC phases or quantum critical points in amplifying these effects.

Liquid helium-cooled high-purity copper coil for generation of long pulsed magnetic fields.

To generate long-duration pulsed magnetic fields with low energy consumption, we present a practical setup that implements an electromagnet made of high-purity copper (99.9999%). The resistance of the high-purity copper coil decreases from 171 mΩ (300 K) to 19.

Fermi surface and light quasi particles in hourglass nodal chain metal-ReO.

Quantum oscillations (QOs) in magnetic torque and electrical resistivity were measured to investigate the electronic structure of-ReO, a candidate hourglass nodal chain (NC) metal (Dirac loop chain metal). All the de Haas-van Alphen oscillation branches measured at 30 mK in magnetic fields of up to 17.5 T were consistent with first-principles calculations predicting four Fermi surfaces (FSs).

Simultaneous measurement of specific heat and thermal conductivity in pulsed magnetic fields.

We report an experimental setup for simultaneously measuring specific heat and thermal conductivity in feedback-controlled pulsed magnetic fields of 50 ms duration at cryogenic temperatures. A stabilized magnetic field pulse obtained by the feedback control, which dramatically improves the thermal stability of the setup and sample, is used in combination with the flash method to obtain absolute values of thermal properties up to 37.2 T in the 22-16 K temperature range.

Quantum transport evidence of isolated topological nodal-line fermions.

Anomalous transport responses, dictated by the nontrivial band topology, are the key for application of topological materials to advanced electronics and spintronics. One promising platform is topological nodal-line semimetals due to their rich topology and exotic physical properties. However, their transport signatures have often been masked by the complexity in band crossings or the coexisting topologically trivial states.

Dimensional reduction and incommensurate dynamic correlations in the [Formula: see text] triangular-lattice antiferromagnet CaReOCl.

The observation of spinon excitations in the [Formula: see text] triangular antiferromagnet CaReOCl reveals a quasi-one-dimensional (1D) nature of magnetic correlations, in spite of the nominally 2D magnetic structure. This phenomenon is known as frustration-induced dimensional reduction. Here, we present high-field electron spin resonance spectroscopy and magnetization studies of CaReOCl, allowing us not only to refine spin-Hamiltonian parameters, but also to investigate peculiarities of its low-energy spin dynamics.

Magnetically Hidden State on the Ground Floor of the Magnetic Devil's Staircase.

We investigated the low-temperature and high-field thermodynamic and ultrasonic properties of SrCu_{2}(BO_{3})_{2}, which exhibits various plateaux in its magnetization curve above 27 T, called a magnetic Devil's staircase. The results of the present study confirm that magnetic crystallization, the first step of the staircase, occurs above 27 T as a first-order transition accompanied by a sharp singularity in heat capacity C_{p} and a kink in the elastic constant. In addition, we observe a thermodynamic anomaly at lower fields around 26 T, which has not been previously detected by any magnetic probes.

Emergent anisotropy in the Fulde-Ferrell-Larkin-Ovchinnikov state.

Exotic superconductivity is formed by unconventional electron pairing and exhibits various unique properties that cannot be explained by the basic theory. The Fulde-Ferrell-Larkin-Ovchinnikov (FFLO) state is known as an exotic superconducting state in that the electron pairs have a finite center-of-mass momentum leading to a spatially modulated pattern of superconductivity. The spatial modulation endows the FFLO state with emergent anisotropy.

Spin-glass transition in the spin-orbit-entangled J = 0 Mott insulating double-perovskite ruthenate.

We have successfully synthesized new Ru double perovskite oxides SrLaInRuO and SrLaGaRuO, which are expected to be a spin-orbit coupled J = 0 Mott insulating ground state. Their magnetic susceptibility is much significant than that expected for a single Ru ion for which exchange coupling with other ions is negligible. Their isothermal magnetization process suggests that there are about 20 percent isolated spins.

Nuclear magnetic resonance measurements in dynamically controlled field pulse.

We present the architecture of the versatile nuclear magnetic resonance (NMR) spectrometer with software-defined radio technology and its application to the dynamically controlled pulsed magnetic fields. The pulse-field technology is the only solution to access magnetic fields greater than 50 T, but the NMR experiment in the pulsed magnetic field was difficult because of the continuously changing field strength. The dynamically controlled field pulse allows us to perform NMR experiment in a quasi-steady field condition by creating a constant magnetic field for a short time around the peak of the field pulse.

High-resolution calorimetry in pulsed magnetic fields.

We have developed a new calorimeter for measuring the thermodynamic properties in pulsed magnetic fields. Instrumental design is described along with the instrument construction details, including the sensitivity of a RuO thermometer. Operation of the calorimeter is demonstrated by measuring the heat capacity of three samples: pure germanium, CeCuGe, and κ-(BEDT-TTF)Cu[N(CN)]Br, in pulsed fields up to 43.

Compact megajoule-class pulsed power supply for generating long-pulsed magnetic fields.

A pulsed power supply with a compact and low-cost electric-double-layer-capacitor (EDLC) is developed for generating pulsed magnetic fields with a long pulse duration of a few seconds. The system is demonstrated in three experimental setups using a 10.7 F- or 50 F-EDLC capacitor bank.

High-field phase diagram of NiVOstudied by specific heat and magnetocaloric effect measurements.

The-phase diagram of NiVOis very rich and remains puzzling in a high magnetic field range. Through the state-of-the-art specific heat measurement in pulsed high field to 35 T and magnetocaloric effect measurement up to 45 T, we successfully construct the high-field phase diagram of NiVOfor fields applied along theaxis. The phase boundaries are corrected for previous results by magnetization and magneto-optical measurements.

Ligand dependent magnetism of theJeff= 3/2 Mott insulator Cs(= Ta, Nb,= Br, Cl).

Magnetic and structural properties of double perovskite type bromides CsBr(= Ta, Nb), where Ta(5) and Nb(4) ions form the face centered cubic lattice, are investigated and compared with chlorides CsCl. CsTaBrexhibits the effective magnetic moment of 0.24, which is much smaller than the spin only value of aion, 1.

Particle-Hole Symmetry Breaking in a Spin-Dimer System TlCuCl_{3} Observed at 100 T.

The entire magnetization process of TlCuCl_{3} has been experimentally investigated up to 100 T employing the single-turn technique. The upper critical field H_{c2} is observed to be 86.1 T at 2 K.

Improved accuracy in high-frequency AC transport measurements in pulsed high magnetic fields.

We show theoretically and experimentally that accurate transport measurements are possible even within the short time provided by pulsed magnetic fields. For this purpose, a new method has been devised, which removes the noise component of a specific frequency from the signal by taking a linear combination of the results of numerical phase detection using multiple integer periods. We also established a method to unambiguously determine the phase rotation angle in AC transport measurements using a frequency range of tens of kilohertz.

Anisotropic Fully Gapped Superconductivity Possibly Mediated by Charge Fluctuations in a Nondimeric Organic Complex.

We investigate low-temperature electronic properties of the nondimeric organic superconductor β^{''}-(ET)_{4}[(H_{3}O)Ga(C_{2}O_{4})_{3}]PhNO_{2}. By examining ultrasonic properties, charge disproportionation (CD) without magnetic field dependence is detected below T_{CD}∼8  K just above the superconducting critical temperature T_{c}∼6  K. From quantum oscillations in high fields, we find variation in the Fermi surface and mass enhancement induced by the CD.

Synthesis, Structure, and Anomalous Magnetic Ordering of the Spin-1/2 Coupled Square Tetramer System K(NbO)Cu(PO).

Quasi-zero-dimensional antiferromagnets with weakly coupled clusters of multiple spins can provide an excellent platform for exploring exotic quantum states of matter. Here, we report the synthesis and the characterization of a copper-based insulating antiferromagnet, K(NbO)Cu(PO). Single-crystal X-ray diffraction measurements reveal that the crystal structure belongs to the tetragonal space group 4/, in which Cu ions align to form a quasi-two-dimensional layer of spin-1/2 coupled square tetramers.