Kazuhiro Nawa 교수

A polymorph of RuI$_3$ synthesized under high pressure was found to have a two-layered honeycomb structure. The resistivity of RuI$_3$ exhibits a semimetallic behavior, in contrast to insulating properties in $\alpha$-RuCl$_3$. In addition, Pauli paramagnetic behavior was observed in the temperature dependence of a magnetic susceptibility and a nuclear spin-lattice relaxation rate 1/$T_1$. The band structure calculations indicate that contribution of the I 5$p$ components to the low-energy $t_\m

A new spin-1/2 quasi-one-dimensional antiferromagnet KCuMoO4(OH) is prepared by the hydrothermal method. The crystal structures of KCuMoO4(OH) and the already-known Na-analogue NaCuMoO4(OH) are isotypic, comprising chains of Cu2+ ions in edge-sharing CuO4(OH)2 octahedra. Despite the structural similarity, their magnetic properties are quite different because of the different arrangements of dx2–y2 orbitals carrying spins. For NaCuMoO4(OH), dx2–y2 orbitals are linked by superexchange couplings vi

The phase diagram of the quasi-one-dimensional magnet ${\mathrm{NaCuMoO}}_{4}(\mathrm{OH})$ is established through single-crystal NMR and heat-capacity measurements. The $^{23}\mathrm{Na}$ and $^{1}\mathrm{H}$ NMR experiments indicate a spiral and a collinear spin density wave (SDW) order below and above ${B}_{c}$ = 1.5--1.8 T, respectively. Moreover, in the paramagnetic state above the SDW transition temperature, the nuclear spin-lattice relaxation rate $1/{T}_{1}$ indicates anisotropic spin fl

This work presents the inelastic neutron scattering spectrum on the spin-1/2 anisotropic triangular lattice antiferromagnetCa_3 ReO_5 Cl_2 , and show that the spinon-like continuum coexists with dispersive modes due to the formation of bound spinon pairs.

A magnetic phase diagram of the non-Heisenberg Tsai-type 1/1 Au-Ga-Tb approximant crystal (AC) has been established across a wide electron-per-atom (e/a) range via magnetization and powder neutron diffraction measurements. The diagram revealed exotic ferromagnetic (FM) and antiferromagnetic (AFM) orders that originate from the unique local spin icosahedron common to icosahedral quasicrystals (iQCs) and ACs; The noncoplanar whirling AFM order is stabilized as the ground state at the e/a of 1.72 o

A magnetic structure of the sawtooth-chain antiferromagnet [Formula: see text] was investigated by magnetization measurements, single crystalline and powder neutron diffraction experiments, and a further analysis on the Mössbauer spectra. These experiments revealed a nearly collinear antiferromagnetic structure with magnetic moments aligned along the b-axis, indicating dominant antiferromagnetic exchanges between Fe(1)-Fe(2) and Fe(2)-Fe(3) sites. The magnon dispersion relation derived from the

The magnetic properties of the quasicrystal approximant ${\mathrm{Au}}_{65}{\mathrm{Ga}}_{21}{\mathrm{Tb}}_{14}$ were investigated using magnetization and neutron diffraction experiments. The temperature dependences of the magnetic susceptibility and magnetization curve indicate dominant ferromagnetic interactions, whereas a whirling antiferromagnetic order was observed in neutron diffraction experiments. In the antiferromagnetic phase, the magnetic moments are aligned almost perpendicular to a

We report on the dynamics of the spin-1/2 quasi-one-dimensional frustrated magnet ${\mathrm{LiCuVO}}_{4}$ measured by nuclear spin relaxation in high magnetic fields 10--34 T, in which the ground state has spin-density-wave order. The spin fluctuations in the paramagnetic phase exhibit striking anisotropy with respect to the magnetic field. The transverse excitation spectrum probed by $^{51}\mathrm{V}$ nuclei has an excitation gap, which increases with field. On the other hand, the gapless longi

Pb2V3O9 was found to have antiferromagnetic alternating chains of S=1/2 and show the antiferromagnetic long range ordered (AFLRO) state under the magnetic field between 4 and 38 T. We succeeded in growing single crystals of Pb2V3O9 by floating zone method and determined the asymmetric H-T phase diagram of Pb2V3O9 from measurements of the magnetization and the heat capacity. Previous reports focused on the AFLRO state in the low magnetic field region and that in high magnetic field region was not

We investigated magnetic and thermodynamic properties of $S=\frac{1}{2}$ quasi-one-dimensional antiferromagnet ${\mathrm{KCuMoO}}_{4}(\mathrm{OH})$ through single-crystalline magnetization and heat capacity measurements. At zero field, it behaves as a uniform $S=\frac{1}{2}$ Heisenberg antiferromagnet with $J=238\phantom{\rule{0.28em}{0ex}}\mathrm{K}$, and exhibits a canted antiferromagnetism below ${T}_{\mathrm{N}}=1.52\phantom{\rule{0.28em}{0ex}}\mathrm{K}$. In addition, a magnetic field $H$ i

Abstract A magnetic order of the quasicrystal approximant Au 70 Al 16 Tb 14 was investigated via single crystalline neutron diffraction experiments. In spite of some differences in the macroscopic magnetic properties compared with Au 72 Al 14 Tb 14 , the whirling antiferromagnetic structure similar to Au 72 Al 14 Tb 14 was found. The robustness of the magnetic structure suggests the orientation of the magnetic moment dominated by easy-axis anisotropy of Tb. In addition, the critical exponent β i

In an ideal classical pyrochlore antiferromagnet without perturbations, an infinite degeneracy in a ground state leads to the absence of magnetic order and a spin-glass transition. Here we present ${\mathrm{Na}}_{3}\mathrm{Mn}{({\mathrm{CO}}_{3})}_{2}\mathrm{Cl}$ as a new candidate compound where classical spins are coupled antiferromagnetically on the pyrochlore lattice and report its structural and magnetic properties. The temperature dependences of the magnetic susceptibility and heat capacit

We synthesized single crystals of NH4CuPO4 · H2O by a chemical reaction in aqueous solutions. Magnetization and specific heat are well reproduced by a dimer model, and NH4CuPO4 · H2O does not show any field-induced magnetic phase transitions. The interdimer interactions would be too weak to observe field-induced phase transitions.

In a frustrated J1–J2 chain magnet with ferromagnetic nearest neighbor interactions J1 and antiferromagnetic next-nearest neighbor interactions J2, novel quantum states such as a spin nematic state are theoretically expected to be present. To detect the novel states experimentally, it is required to find a suitable model compound and to obtain its sizeable and high-quality single crystals. Here we report synthesis of a single-crystalline NaCuMoO4(OH), a model compound of frustrated J1–J2 chain m