A hidden order that emerges in the frustrated pyrochlore Tb2+xTi2-xO7+y with Tc = 0.53 K is studied using neutron scattering, specific heat, magnetization measurements on a high-quality single crystal. Semiquantitative analyses based on a pseudospin-1/2 Hamiltonian for ionic non-Kramers magnetic doublets demonstrate that it is a long-range order of electric quadrupole moments intrinsic to the Tb3+ ions. This is the first example of electric quadrupole order in frustrated magnetic systems, and opens new research directions for "frustrated quadrupole systems". It is also found that the elusive spin liquid state of the nominal Tb2Ti2O7, studied for more than a decade, is most likely a U(1) quantum spin-liquid state.
A cubic 4f2 system PrIr2Zn20 exhibits a superconducting transition at 0.05 K below a quadrupolar transition at 0.11 K. We have conducted neutron diffraction measurements in magnetic fields B ≤ 5 T down to 0.04 K to determine the order parameter expected for the non-Kramers ground state doublet. Field-induced magnetic reflection appears at Q = (1/2, 1/2, –3/2) together with some of its equivalents in B || [1 −1 0]. Thus, the antiferroquadrupole order is characterized by the propagation vector q = (1/2, 1/2, 1/2). The magnetic-structure-factor analysis revealed that the magnetic moments are induced along the [1 1 1] axis on the Pr-ion diamond sublattice. In contrast, no reflections appear for B || [0 0 1] as well as in zero field. The results indicate that the O22-type quadrupole is the primary order parameter which entangles with other various multipolar degrees of freedom. Such entanglements should play the role in the enriched B-T phase diagram of PrIr2Zn20 including the non-Fermi liquid state and field-induced Fermi liquid state.
Tensile strength tests were performed to evaluate strength of thin-walled aluminum cylinders for designing a sample cell using neutron experimental study. The results showed that some trends were observed in tensile strength, on the other hand, it was limited to the influence of each maximum allowable pressure of the cylinders. Based on the results, a web page to estimate reasonable parameters of the cell was provided.
The high-power pulsed spallation neutron source is one of the most convenient tools to conduct cutting-edge research in several domains of materials and life science. In this system, proton beams of several hundred kW to MW order extracted from the high power accelerator is injected into a target and vast amount of neutrons are generated via the spallation reactions with the target material nuclei. The neutron beams are then supplied to the state-of-the-art suite of various experimental devices for fundamental research activities. In this paper outline of the spallation neutron source, target design and technical topics are reviewed by referring mainly to the mercury target system of J-PARC.