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The High Resolution Chopper Spectrometer (HRC) is installed at the Japan Proton Accelerator Research Complex (J-PARC) and is utilized for a wide range of dynamical studies of materials over a wide energy-momentum space with high resolution. Neutron Brillouin scattering (NBS), i.e., inelastic neutron scattering close to the forward direction, can be performed with the HRC, because this instrument utilizes low angle detectors and high-energy neutrons which facilitates a high resolution. Since the solid angle of the detection area for NBS experiments is limited to very low scattering angles, improvements of the HRC are required to increase the neutron flux with reducing the background. Given the success of the HRC for NBS studies, the neutron intensities for NBS experiments have been improved by changing the detector layout, reducing deformation of the slit package during rotation of the Fermi chopper, and fabricating a longer collimator. At present, we have made further improvements. At around the incident neutron energy Ei = 100 meV, the neutron flux was significantly increased for an energy resolution of ΔE∕Ei = 2%, and the best energy resolution achieved was nearly 1% resolution with an acceptable neutron flux.

We present acoustic signatures of the electric quadrupolar degrees of freedom in the honeycomb-layer compound UNi$_4$B. The transverse ultrasonic mode $C_{66}$ shows softening below 30 K both in the paramagnetic phase and antiferromagnetic phases down to $\sim0.33$ K. Furthermore, we traced magnetic field-temperature phase diagrams up to 30 T and observed a highly anisotropic elastic response within the honeycomb layer. These observations strongly suggest that $\Gamma_6$(E$_{\rm 2g}$) electric quadrupolar degrees of freedom in localized $5f^2$ ($J = 4$) states are playing an important role in the magnetic toroidal dipole order and magnetic-field-induced phases of UNi$_4$B, and evidence some of the U ions remain in the paramagnetic state even if the system undergoes magnetic toroidal ordering., Comment: 6 pages, 4 figures + Supplemental Materials (11 pages, 9 figures)

We have performed a susceptibility M / H and 11 B NMR measurements to investigate the static magnetic anisotropy of a single crystal UNi 4 B. The Knight shift 11 K and the hyperfine coupling constant A hf evaluated by 11 K - M / H plot show anisotropic behavior between H ∥ [ 11 2 ¯ 0 ] and H ∥ [ 0001 ] , reflecting the bulk susceptibility. The evaluated transferred term A tr of A hf for H ∥ [ 11 2 ¯ 0 ] is much larger than the one for H ∥ [ 0001 ] . The strong hybridization in the [0001]-plane due to a itinerant 5 f -electron is strongly associated with the unique magnetic structure in this compound.

The crystal structure of the magnetoelectric metal UNi4B was determined from high-resolution synchrotron X-ray diffraction experiments using single-crystalline samples. The direct method and the le...

Thermal expansion, magnetostriction, and magnetization measurements under magnetic field and hydrostatic pressure were performed on a ${\mathrm{UAu}}_{2}{\mathrm{Si}}_{2}$ single crystal. They revealed a large anisotropy of magnetoelastic properties manifested by prominent length changes, leading to a collapse of the unit-cell volume accompanied by breaking the fourfold symmetry (similar to that in ${\mathrm{URu}}_{2}{\mathrm{Si}}_{2}$ in the hidden-order state) in the antiferromagnetic state as consequences of strong magnetoelastic coupling. The magnetostriction curves measured at higher temperatures confirm a bulk character of the $50\phantom{\rule{0.16em}{0ex}}\mathrm{K}$ weak ferromagnetic phase. The large positive pressure change of the ordering temperature predicted from Ehrenfest relation contradicts the more than an order of magnitude smaller pressure dependence observed by the magnetization and specific heat measured under hydrostatic pressure. A comprehensive magnetic phase diagram of ${\mathrm{UAu}}_{2}{\mathrm{Si}}_{2}$ in magnetic field applied along the $c$ axis is presented. The ground-state antiferromagnetic phase is suppressed by a field-induced metamagnetic transition that changes its character from second to first order at the tricritical point.

We have performed electrical-resistivity measurements under hydrostatic pressures ranging up to 4.47 GPa on the cubic compound CeAg. A pressure–temperature phase diagram has been revised in a high-pressure range above ∼ 2.1 GPa , where the system is known to enter into an unidentified phase through a first-order phase transition. We have found that the electrical resistivity shows a clear kink anomaly below ∼ 4 K in this unknown phase. The anomaly shifts to lower temperature with increasing pressure, and shows a tendency to reach absolute zero at ∼ 6 GPa , suggesting the presence of a pressure-induced quantum critical point around this pressure. We have also observed that a first-order phase boundary line, which separates the phase diagram into two regions of a tetragonal phase and the unidentified phase, seems to terminate in a critical end point located at ( P CEP , T CEP ) ∼ ( 3.2 GPa , 200 K ) . This suggests that the crystal symmetry of the unidentified phase above ∼ 2.1 GPa is also tetragonal.

Magnetic structure of tetragonal UAu$_2$Si$_2$ was investigated by single-crystal neutron diffraction experiments. Below $T_{\rm N}$ = 20 K it orders antiferromagnetically with a propagation vector of $k = (2/3, 0, 0)$ and magnetic moments of uranium ions pointing along the tetragonal $c$-axis. Weak signs of the presence of a ferromagnetic component of magnetic moment were traced out.Taking into account a group theory calculation and experimental results of magnetization and $^{29}$Si-NMR, the magnetic structure is determined to be a squared-up antiferromagnetic structure, with a stacking sequence ($+ + -$) of the ferromagnetic $ac$-plane sheets along the $a$-axis. This result highlights similar magnetic correlations in UAu$_2$Si$_2$ and isostructural URu$_2$Si$_2$., Comment: 7 pages, 7 figures

Single-crystalline UAu$_2$Si$_2$ has been grown by a floating-zone melting method, and its magnetic, thermal and transport properties have been investigated through measurements of magnetization, specific heat and electrical resistivity to reveal its peculiar magnetism. It is shown that UAu$_2$Si$_2$ undergoes a second-order phase transition at \tm = 19 K, which had been believed to be ferromagnetic ordering in the literature, from a paramagnetic phase to an uncompensated antiferromagnetic phase with spontaneous magnetization along the tetragonal $c$-axis (the easy magnetization direction). The magnetic entropy analysis points to the itinerant character of 5f electrons in the magnetic ordered state of UAu$_2$Si$_2$ with large enhancement of the electronic specific heat coefficient of $\gamma$ $\sim$ 150 mJ/K$^2$mol at 2 K. It also reveals the relatively isotropic crystalline electric field effect of this compound, with contrast to the other relative isostructural compounds. The observed magnetization curves strongly suggest that there is a parasitic ferromagnetic component developing below $\sim$ 50 K in high coercivity with the easy axis along the tetragonal $c$-axis. The results are discussed in the context of evolution of magnetism within the entire family of isostructural U$T_2$Si$_2$ compounds., Comment: 13 pages, 21 figures

Magnetization measurements under direct electric current were performed in a toroidal magnetic ordered state of UNi4B to test a recent theoretical prediction of current-induced magnetization in a metallic system lacking local-inversion symmetry. We found that electric current parallel to \([2\bar{1}\bar{1}0]\) and [0001] in the hexagonal 4-index notation induces a uniform magnetization along the \([01\bar{1}0]\) direction. The observed behavior of the induced magnetization is essentially consistent with the theoretical prediction; however, it also shows an inconsistency suggesting that the antiferromagnetic state of UNi4B could not be simply regarded as a uniform toroidal order in the ideal honeycomb layered structure.

Ultrasonic investigations of the elastic constants of non-5f compound ThRu2Si2 were performed in order to highlight possible quadrupolar response in the elastic constants of heavy fermion compound URu2Si2, by using the ThRu2Si2 for backgrounds to subtract the phonon contributions in the elastic constants of URu2Si2. We confirmed that the all-elastic constants of ThRu2Si2 show no elastic anomaly, i.e., increasing monotonically and saturating toward low temperatures, which can be understood regular phonon contributions for the solid states. The background-subtracted (C11-C12)/2 of URu2Si2 keeps decreasing with decreasing temperatures from 300 K, while other share modes C44 and C66 show little change. These contrasts suggest that the Γ3-type quadrupole moment O22 will be still dominant and active in URu2Si2 at low temperatures.

Ultrasonic measurements on Rh-substitution system U(Ru1−xRhx)2Si2 (x = 0, 0.02 and 0.07) were performed in order to investigate lattice properties for low temperature phase transitions of 'hidden order' (HO) phase and antiferromagnetc (AFM) phase. Elastic constant C11 vs. T of the x = 0.02 and 0.07 samples exhibit a depression below 80 K, which is similar to a softening in the non-doped sample which had already been reported. The C11 of x = 0.02 exhibits a step-like anomaly at 14.0 K and an additional softening of 3.2% with minimum at 6.7 K, which correspond to HO and AFM transitions, respectively. The C11 in x = 0.07 sample only exhibits a shoulder-like anomaly at around 17 K and continue to depress down to 4.2 K.

The sequence of about 4,500 nucleotides of the internal part of tobacco mosaic virus (TMV)-tomato strain (L) RNA has been newly determined using cloned cDNAs. Together with the previously determined partial sequences at both ends, the entire sequence of the 6,384 nucleotide genome has been completed. The 130K (1,115 amino acids), 180K (1,615 amino acids), 30K (263 amino acids) and coat protein (158 amino acids) cistrons are located at residues 72-3442, 72-4922, 4906-5700, and 5703-6182 on the genome, respectively. Sequence polymorphism was not observed except for heterogeneity in the length of the A cluster near the 3' end. The homology of the nucleotide sequences of TMV-L and TMV-vulgare, a common strain, is about 80% on average. Remarkable differences between them were found in a part of the N-terminal portion of the 130K/180K protein and the C-terminal portion of the 30K protein. A new method for cDNA cloning was developed by which the cDNA of the 5'-terminus of viral RNA can be cloned efficiently.