548 research outputs found

    Singlet Ground State and Magnetization Plateaus in Ba3_3Mn2_2O8_8

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    Magnetic susceptibility and the magnetization process have been measured in \green polycrystal. In this compound, the magnetic manganese ion exists as Mn5+^{5+} in a tetrahedral environment, and thus the magnetic interaction can be described by an S=1 Heisenberg model. The ground state was found to be a spin singlet with an excitation gap Δ/kB=11.2\Delta/k_{\rm B}=11.2 K. Magnetization plateaus were observed at zero and at half of the saturation magnetization. These results indicate that the present system can be represented by a coupled antiferromagnetic dimer model.Comment: 4 pages, 4 figures, jpsj styl

    Generation of tunable Terahertz out-of-plane radiation using Josephson vortices in modulated layered superconductors

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    We show that a moving Josephson vortex in spatially modulated layered superconductors generates out-of-plane THz radiation. Remarkably, the magnetic and in-plane electric fields radiated are of the same order, which is very unusual for any good-conducting medium. Therefore, the out-of-plane radiation can be emitted to the vacuum without the standard impedance mismatch problem. Thus, the proposed design can be more efficient for tunable THz emitters than previous proposals, for radiation only propagating along the ab-plane.Comment: 7 pages, 1 figure. Phys. Rev. B (2005), in pres

    Observation of Field-Induced Transverse N\'{e}el Ordering in the Spin Gap System TlCuCl3_3

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    Neutron elastic scattering experiments have been performed on the spin gap system TlCuCl3_3 in magnetic fields parallel to the bb-axis. The magnetic Bragg peaks which indicate the field-induced N\'{e}el ordering were observed for magnetic field higher than the gap field Hg5.5H_{\rm g}\approx 5.5 T at Q=(h,0,l)Q=(h, 0, l) with odd ll in the aca^*-c^* plane. The spin structure in the ordered phase was determined. The temperature and field dependence of the Bragg peak intensities and the phase boundary obtained were discussed in connection with a recent theory which describes the field-induced N\'{e}el ordering as a Bose-Einstein condensation of magnons.Comment: 4 pages, 5 eps figures, jpsj styl

    Superconductivity in CVD Diamond Thin Film Well-Above Liquid Helium Temperature

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    Diamond has always been adored as a jewel. Even more fascinating is its outstanding physical properties; it is the hardest material known in the world with the highest thermal conductivity. Meanwhile, when we turn to its electrical properties, diamond is a rather featureless electrical insulator. However, with boron doping, it becomes a p-type semiconductor, with boron acting as a charge acceptor. Therefore the recent news of superconductivity in heavily boron-doped diamond synthesized by high pressure sintering was received with considerable surprise. Opening up new possibilities for diamond-based electrical devices, a systematic investigation of these phenomena clearly needs to be achieved. Here we show unambiguous evidence of superconductivity in a diamond thin film deposited by a chemical vapor deposition (CVD) method. Furthermore the onset of the superconducting transition is found to be 7.4K, which is higher than the reported value in ref(7) and well above helium liquid temperature. This finding establishes the superconductivity to be a universal property of boron-doped diamond, demonstrating that device application is indeed a feasible challenge.Comment: 6 pages, 3 figure

    Field-induced magnetic ordering in the Haldane system PbNi2V2O8

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    The Haldane system PbNi2V2O8 was investigated by the temperature dependent magnetization M(T) measurements at fields higher than H_c, with H_c the critical fields necessary to close the Haldane gap. It is revealed that M(T) for H > H_c exhibits a cusp-like minimum at T_{min}, below which M(T) increases with decreasing T having a convex curve. These features have been observed for both HcH \parallel c and HcH \perp c, with c-axis being parallel to the chain. These data indicate the occurrence of field-induced magnetic ordering around T_{min}. Phase boundaries for HcH \parallel c and HcH \perp c do not cross each other, consistent with the theoretical calculation for negative single-ion anisotropy D.Comment: 3 figures, submitted to Phys. Rev.
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