77 research outputs found

    Magnetic Properties of YbBe13 Probed by Neutron Scattering and Thermodynamic Measurements

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    We examined the magnetic properties of YbBe13, which exhibits an antiferromagnetic order below TN = 1.2 K. Unlike other MBe13 compounds (M = rare earth/actinide elements), based on elastic neutron scattering, we observed an incommensurate magnetic propagation vector {\tau} = (0,0,{\tau}z), where {\tau}z = 0.5385 is in the reciprocal lattice unit. Additionally, we constructed a precise magnetic phase diagram for YbBe13. We observed non-trivial magnetic anomalies in YbBe13, which cannot be understood based on a simple helical order. Our results for YbBe13 provide an opportunity to reconsider the electron state of UBe13 and present an important step toward a comprehensive understanding of magnetic correlations in MBe13 series.Comment: 5 pages, 5 figure

    Pressure-induced structural phase transition and new superconducting phase in UTe2

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    We report on the crystal structure and electronic properties of the heavy fermion superconductor UTe2 at high pressure up to 11 GPa, as investigated by X-ray diffraction and electrical resistivity experiments. The X-ray diffraction measurements under high pressure using a synchrotron light source reveal anisotropic linear compressibility of the unit cell up to 3.5 GPa, while a pressure-induced structural phase transition is observed above 3.5-4GPa at room temperature, where the body-centered orthorhombic crystal structure with the space group Immm changes into a body-centered tetragonal structure with the space group I4/mmm. The molar volume drops abruptly at the critical pressure, while the distance between the first-nearest neighbor of U atoms increases, implying a switch from the heavy electronic states to the weakly correlated electronic states. Surprisingly, a new superconducting phase at pressures higher than 7 GPa was detected at Tsc above 2K with a relatively low upper-critical field, Hc2(0). The resistivity above 3.5GPa, thus, in the high-pressure tetragonal phase, shows a large drop below 230 K, which may also be related to a considerable change from the heavy electronic states to the weakly correlated electronic states.Comment: 11 pages, 9 figure

    Orientation of point nodes and nonunitary triplet pairing tuned by the easy-axis magnetization in UTe2

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    The gap structure of a novel uranium-based superconductor UTe2_2, situated in the vicinity of ferromagnetic quantum criticality, has been investigated via specific-heat C(T,H,Ω)C(T,H,\Omega) measurements in various field orientations. Its angular Ω(ϕ,θ)\Omega(\phi,\theta) variation shows a characteristic shoulder anomaly with a local minimum in HaH \parallel a at moderate fields rotated within the abab and acac planes. Based on the theoretical calculations, these features can be attributed to the presence of point nodes in the superconducting gap along the aa direction. Under the field orientation along the easy-magnetization aa axis, an unusual temperature dependence of the upper critical field at low fields together with a convex downward curvature in C(H)C(H) were observed. These anomalous behaviors can be explained on the basis of a nonunitary triplet state model with equal-spin pairing whose TcT_{\rm c} is tuned by the magnetization along the aa axis. From these results, the gap symmetry of UTe2_2 is most likely described by a vector order parameter of d(k)=(b+ic)(kb+ikc)d(k)=(b + ic)(k_b + ik_c).Comment: 6 pages, 4 figures (main text) + 7 pages, 5 figures (Supplementary Material), accepted for publication in Phys. Rev. Researc
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