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Ferromagnetism and spin-glass transitions in the Heusler compounds Ru2−xFexCrSi

Physical Review B 2009年第22期79卷 224423-224423页

作者： Masahiko Hiroi Tsugumi Rokkaku Kazuhisa Matsuda Toru Hisamatsu Iduru Shigeta Masakazu Ito Takuo Sakon Keiichi Koyama Kazuo Watanabe Shintaro Nakamura Tsutomu Nojima Tomohito Nakano Lin Chen Tetsuya Fujiwara Yoshiya Uwatoko Hirotaka Manaka Norio Terada Department of Physics and Astronomy Graduate School of Science and Engineering Kagoshima University Kagoshima 890-0065 Japan Center for Geo-Environmental Science Faculty of Engineering and Resource Science Akita University Tegata-Gakuenmachi Akita City 010-8502 Japan High Field Laboratory for Superconducting Materials Institute for Materials Research Tohoku University Katahira Sendai 980-8577 Japan Center for Low Temperature Science Tohoku University Katahira Sendai 980-8577 Japan Department of Physics Kyushu University Fukuoka 812-8581 Japan Institute for Solid State Physics University of Tokyo Kashiwanoha Kashiwa Chiba 277-8581 Japan Graduate School of Science and Engineering Yamaguchi University Yamaguchi 753-8512 Japan Department of Electrical and Electronics Engineering Graduate School of Science and Engineering Kagoshima University Kagoshima 890-0065 Japan

The results of a comprehensive study of the structural, magnetic, and magnetotransport properties of the Heusler compounds Ru2−xFexCrSi are presented. The Fe-rich compounds (x≥1.5) exhibit a usual ferromagnetic transition. The Ru-rich compound (x=0.1) does not show ferromagnetism but exhibits a peak in magnetic susceptibility at TN∗=30 K. Nevertheless, specific-heat measurements show that there is no antiferromagnetic transition at TN∗ nor at any other temperatures. With further decreasing temperature strong irreversible behavior occurs below a temperature Tg. It is proposed that these results can be interpreted as successive spin-glass transitions at TN∗ and Tg. The compounds with intermediate x (=0.3 and 0.5) are found to be ferromagnetic. Both the saturation magnetization and the Curie temperature TC increase with increasing x. However, being different from the Fe-rich compounds, hysteresis of the magnetization is observed and this suggests that the ferromagnetism has glassy character. In lower-temperature range fairly large negative magnetoresistance are observed. These results are suggestive of a magnetically inhomogeneous ferromagnetic state, that is, the formation of ferromagnetic clusters.

关键词： chromium alloys Curie temperature ferromagnetic materials iron alloys magnetic hysteresis magnetic susceptibility magnetic transitions magnetoresistance ruthenium alloys silicon alloys specific heat spin glasses

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Weakly Coupled s=1/2 Quantum Spin Singlets in Ba3Cr2O8

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Physical Review Letters 2009年第3期102卷 037206-037206页

作者： M. Kofu J.-H. Kim S. Ji S.-H. Lee H. Ueda Y. Qiu H.-J. Kang M. A. Green Y. Ueda Department of Physics University of Virginia Charlottesville Virginia 22904-4714 USA NIST Center for Neutron Research Gaithersburg Maryland 20899-6100 USA Institute for Solid State Physics University of Tokyo Kashiwa 277-8581 Japan Department of Materials Science and Engineering University of Maryland College Park Maryland 20742-6393 USA

Using single crystal inelastic neutron scattering with and without the application of an external magnetic field and powder neutron diffraction, we have characterized magnetic interactions in Ba3Cr2O8. Even without a field, we found that there exist three singlet-to-triplet excitation modes in the (h, h, l) scattering plane. Our complete analysis shows that the three modes are due to spatially anisotropic interdimer interactions that are induced by lattice distortions of the tetrahedron of oxygens surrounding the Jahn-Teller active Cr5+(3d1). The strong intradimer coupling of J0=2.38(2) meV and weak interdimer interactions (|Jinter|≤0.52(2) meV) makes Ba3Cr2O8 a good model system for weakly coupled s=1/2 quantum spin dimers.

关键词： Chromium compounds

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Ishizaka et al. Reply:

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Physical Review Letters 2009年第19期102卷 199702-199702页

作者： K. Ishizaka R. Eguchi S. Tsuda A. Chainani T. Yokoya T. Kiss T. Shimojima T. Togashi S. Watanabe C.-T. Chen Y. Takano M. Nagao I. Sakaguchi T. Takenouchi H. Kawarada S. Shin Institute for Solid State Physics University of Tokyo Kashiwa Chiba 277-8581 Japan National Institute for Materials Science Tsukuba Ibaraki 305-0047 Japan The Institute of Physical and Chemical Research (RIKEN) Sayo-gun Hyogo 679-5143 Japan The Graduate School of Natural Science and Technology Okayama University Okayama 700-8530 Japan Beijing Center for Crystal R&D Chinese Academy of Science Zhongguancun Beijing 100080 China School of Science and Engineering Waseda University Shinjuku Tokyo 169-8555 Japan

A Reply to the Comment by J. D. Lee et al..

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Soft phonon columns on the edge of the Brillouin zone in the relaxor PbMg1/3Nb2/3O3

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Physical Review B 2009年第22期79卷 224301-224301页

作者： I. P. Swainson C. Stock P. M. Gehring Guangyong Xu K. Hirota Y. Qiu H. Luo X. Zhao J.-F. Li D. Viehland National Research Council Chalk River Ontario Canada KOJ 1JO ISIS Facility Rutherford Appleton Laboratory Didcot Oxon OX11 0QX United Kingdom NIST Center for Neutron Research National Institute of Standards and Technology Gaithersburg Maryland 20899 USA Department of Condensed Matter Physics and Materials Science Brookhaven National Laboratory Upton New York 11973 USA Institute for Solid State Physics University of Tokyo Kashiwa 277-8581 Japan Department of Materials Science and Engineering University of Maryland College Park Maryland 20742 USA Shanghai Institute of Ceramics Chinese Academy of Sciences Shanghai 201800 China Department of Materials Science and Engineering Virginia Tech Blacksburg Virginia 24061 USA

We report lattice-dynamical measurements, made using neutron inelastic-scattering methods, of the relaxor perovskite PbMg1/3Nb2/3O3 (PMN) at momentum transfers near the edge of the Brillouin zone. Unusual “columns” of phonon scattering that are localized in momentum, but extended in energy, are seen at both high-symmetry points along the zone edge: Q⃗R={12,12,12} and Q⃗M={12,12,0}. These columns soften at ∼400 K which is similar to the onset temperature of the zone-center diffuse scattering, indicating a competition between ferroelectric and antiferroelectric distortions. We propose a model for the atomic displacements associated with these phonon modes that is based on a combination of structure factors and group theoretical analysis. This analysis suggests that the scattering is not from tilt modes (rotational modes of oxygen octahedra), but from zone-boundary optic modes that are associated with the displacement of Pb2+ and O2− ions. Whereas similar columns of scattering have been reported in metallic and (less commonly) molecular systems, they are unusual in insulating materials, particularly in ferroelectrics; therefore, the physical origin of this inelastic feature in PMN is unknown. We speculate that the underlying disorder contributes to this unique anomaly.

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Cover Picture: Photoelectron Generation by Photosystem II Core Complexes Tethered to Gold Surfaces (ChemSusChem 4/2010)

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ChemSusChem 2010年第4期3卷 393-393页

作者： Michele Vittadello Prof. Maxim Y. Gorbunov Prof. Daniel T. Mastrogiovanni Leszek S. Wielunski Dr. Eric L. Garfunkel Prof. Fernando Guerrero Dr. Diana Kirilovsky Dr. Miwa Sugiura Prof. A. William Rutherford Dr. Ahmad Safari Prof. Paul G. Falkowski Prof. Department of Chemistry and Chemical Biology Rutgers The State University of New Jersey 610 Taylor Road Piscataway NJ 08854 (USA) Fax: (+1) 732-932-4083 PECS Department Medgar Evers College of the City University of New York 1650 Bedford Avenue Brooklyn NY 11225 (USA) Environmental Biophysics and Molecular Ecology Program Institute of Marine and Coastal Sciences Rutgers The State University of New Jersey 71 Dudley Road New Brunswick NJ 08901-8521 (USA) Department of Physics Rutgers The State University of New Jersey 619 Allison Road Piscataway NJ 08854 (USA) Unité de Recherche Associée 2096 Centre National de la Recherche Scientifique Service de Bioénergétique 91191 Gif-sur-Yvette (France) Cell-Free Science and Technology Research Center Ehime University Bunkyo-cho Matsuyama Ehime 790-8577 (Japan) Department of Materials Science and Engineering Rutgers The State University of New Jersey 607 Taylor Road Piscataway NJ 08854-8065 (USA)

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Meissner effect in films of ropes of boron-doped single-walled carbon nanotubes;Correlation with applied pressure and boron-doped multi-walled nanotubes

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Journal of Physics: Conference Series 2009年第1期153卷

作者： Matsudaira, M. Nakamura, J. Shimizu, T. Haruyama, J. Reppert, J. Rao, A.M. Eguchi, T. Nishio, T. Hasegawa, Y. Sano, H. Iye, Y. School of Science and Engineerings Material Science Course Aoyama Gakuin University Sagamihara Kanagawa 229-8558 5-10-1 Fuchinobe Japan Institute for Solid State Physics University of Tokyo Kashiwa Chiba 277-8581 Kashiwanoha 5-1-5 Japan Department of Physics and Astronomy Center for Optical Materials Science and Engineering Technologies Clemson University Clemson SC 29634 United States JST-CREST Kawaguchi Saitama 332-0012 4-1-8 Hon-machi Japan

Superconductivity in carbon nanotubes (CNTs) is attracting considerable attention. Recently, we have reported successful boron doping into single-walled CNTs (SWNTs) and also revealed its correlation with superconductivity. In the present study, we report results of pressure-applied magnetization measurements in films consisting of ropes of boron-doped SWNTs. It reveals that Tc and magnitude for Meissner effect is mostly independent of applied pressure, while magnitude of graphite diamagnetism drastically increases as pressure increases. We also report result of resistance measurements in the samples and also correlation of boron doped SWNTs with multi-walled CNTs, in which we reported superconductivity previously. © 2009 IOP Publishing Ltd.

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Intrinsic localized modes observed in the high-temperature vibrational spectrum of NaI

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Physical Review B 2009年第13期79卷 134304-134304页

作者： M. E. Manley A. J. Sievers J. W. Lynn S. A. Kiselev N. I. Agladze Y. Chen A. Llobet A. Alatas Lawrence Livermore National Laboratory Livermore California 94551 USA Laboratory of Atomic and Solid State Physics Cornell University Ithaca New York 14853-2501 USA NIST Center for Neutron Research National Institute of Standards and Technology Gaithersburg Maryland 20899 USA Department of Materials Science and Engineering University of Maryland College Park Maryland 20742 USA Los Alamos National Laboratory Los Alamos New Mexico 87545 USA Argonne National Laboratory Argonne Illinois 60439 USA

Inelastic neutron measurements of the high-temperature lattice excitations in NaI show that in thermal equilibrium at 555 K an intrinsic mode, localized in three dimensions, occurs at a single frequency near the center of the spectral phonon gap, polarized along [111]. At higher temperatures the intrinsic localized mode gains intensity. Higher energy inelastic neutron and x-ray scattering measurements on a room-temperature NaI crystal indicate that the creation energy of the ground state of the intrinsic localized mode is 299 meV.

关键词： ground states high-temperature effects localised modes phonons sodium compounds vibrational modes X-ray scattering

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Reduction of oxide islands on metal surfaces investigated by In-situ UHV TEM

Reduction of oxide islands on metal surfaces investigated by...

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materials science and Technology Conference and Exhibition, MS and T'08

作者： Zhou, Guangwen Dai, Weiying Yang, Judith C. Department of Mechanical Engineering and Multidisciplinary Program in Materials Science and Engineering State University of New York Binghamton United States MR Physics Center Department of Radiology Harvard University United States Department of Mechanical Engineering and Materials Science University of Pittsburgh United States

ISBN: (纸本)9781605606217

Using in situ ultrahigh environmental transmission electron microscopy (UHV-TEM) and atomic force microscopy, we have observed a linear decay behavior of Cu20 nanoislands on Cu(100) surfaces under vacuum annealing. The reduction of these oxide islands leads to the formation of surface craters. Our Monte Carlo simulations reveal that the growth of the crater rim is controlled by the homoepitaxial growth of Cu adatoms displaced from the reducing Cu 20 islands. These observations suggest that the mechanism governing the reduction of oxide nanoislands on metal surfaces is fundamentally different from that for bulk oxides. Copyright © 2008 MS&T'08.

关键词： High resolution transmission electron microscopy

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Spin-glass like behaviour in the nanoporous Fe2O3 with amorphous structure

Spin-glass like behaviour in the nanoporous Fe2O3 with amorp...

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作者： Thakur, M. Majumdar, S. Giri, S. Bhaumik, A. Nandi, M. Nakamura, H. Kobayashi, H. Kohara, T. Department of Solid State Physics Center for Advanced Materials Indian Association for the Cultivation of Science Jadavpur Kolkata 700 032 India Department of Materials Science Center for Advanced Materials Indian Association for the Cultivation of Science Jadavpur Kolkata 700 032 India Graduate School of Material Science University of Hyogo Kamigori Ako-gun Hyogo 678-1297 Japan Department of Materials Science and Engineering Kyoto University Kyoto 606-8501 Japan

The porous Fe2O3 was synthesized chemically. The average size of the particle was ∼85.0 nm, which was observed by scanning electron microscopy. The signature of porous structure was confirmed by a N 2 adsorption/desorption isotherm and intense x-ray powder diffraction peak at low angle. The x-ray diffraction pattern at high angle indicates the amorphous structure. Mössbauer investigations show that the value of the hyperfine field is ∼498.0 kOe at 4.2 K which is much smaller than that of the hyperfine field of crystalline α/γ-Fe2O3 and consistent with the values of amorphous Fe2O3. The temperature dependence of zero-field cooled magnetization exhibits a peak at 18.0 K (Tf), where Tf follows the Almeida-Thouless relation as . The ageing phenomenon of the magnetic relaxation below T f and the memory effect in the field-cooled magnetization indicate the typical features of the classical spin-glass compounds below the spin freezing temperature at Tf. © 2008 IOP Publishing Ltd.

关键词： Spin glass

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Evidence for field-induced quantum critical route to a Fermi liquid in overdoped Tl2Ba2CuO6+x

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Journal of Physics: Conference Series 2009年第5期150卷

作者： T Shibauchi L Krusin-Elbaum M Hasegawa Y Kasahara R Okazaki Y Matsuda Department of Physics Kyoto University Sakyo-ku Kyoto 606–8502 Japan IBM T. J. Watson Research Center Yorktown Heights New York 10598 USA Department of Materials Science and Engineering Nagoya University Chikusa-ku Nagoya 464–8603 Japan Institute for Solid State Physics University of Tokyo Kashiwa Chiba 277–8581 Japan

We report an unanticipated transformation from a non-Fermi- to a Fermi-liquid state driven by magnetic field in a highly overdoped Tl2Ba2CuOe+x with Tc ~ 15 K. From the c-axis resistivity measured up to 45 T, we show that the Fermi-liquid ρc = ρc(0) + AT2 features, accompanied by a field-linear magnetoresistance, appear above a temperature-dependent field HFL, which decreases linearly with decreasing temperature and points to a quantum critical point near the upper critical field HC2(0). The observed field-induced quantum criticality with a power-law diverging A(H) bears a striking resemblance to that of heavy-fermion superconductor CeCoIn5, suggesting a common underlying physics in these strongly correlated electron systems.

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