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389 results on '"Nagasawa, N."'

63. Polarization characteristics of zeolite single crystals containing carbon nanotubes.

Author

Nagasawa, N., Kudryashov, I., Tsuda, S., and Tang, Z. K.

Subjects
*ZEOLITES, *NANOTUBES, *CARBON, *ANISOTROPY
Abstract

Optical polarization anisotropy of single crystals of AlPO[sub 4]-5 (AFI) containing carbon nanotubes is studied to develop the optical characterization method of the samples by laser micro-polarimetry at 488nm. The crystals are opaque in the configuration, K⊥C with EC, but are almost transparent in the configuration, K⊥C with E⊥C, where K and E are the wave vector and the electric field of the incident light, respectively. The degree of polarization reaches almost unity at the maximum. When KC, they are also transparent for any directions of E except for some locations including the surface. The strong luminescence bands are observed at 540nm and 570nm with the tall toward long wavelength region. The 3D imaging of the luminescence is performed by Nanofinder to demonstrate their extrinsic origin. [ABSTRACT FROM AUTHOR]

Published
2001

87. Simultaneous superconducting and antiferroquadrupolar transitions in PrRh2Zn20.

Author

Onimaru, T., Nagasawa, N., Matsumoto, K. T., Wakiya, K., Umeo, K., Kittaka, S., Sakakibara, T., Matsushita, Y., and Takabatake, T.

Subjects
*ZINC compounds, *QUADRUPLETS, *PHASE transitions, *MAGNETIC properties of metals, *SUPERCONDUCTIVITY, *MAGNETIC susceptibility, *ANISOTROPY
Abstract

Superconducting and antiferroquadrupolar (AFQ) transitions in a Pr-based compound PrRh2Zn20 have been found to occur simultaneously at Tc = TQ = 0.06 K. The superconducting transition manifests itself by zero resistance and large diamagnetic susceptibility. The specific heat exhibits a Schottky anomaly peaking at 14 K, and magnetization curves measured at 2 K show anisotropic behaviors. The analysis of these data indicates that the crystalline electric field ground state ofthe trivalent Pr ion is the non-Kramers T3 doublet with the quadrupolar degrees of freedom. A sharp peak in the specific heat at 0.06 K has been attributed not to the superconducting transition but to the AFQ transition because the ordering temperature TQ decreases in B || [100] but increases in B || [110] and B || [11||] with increasing B up to 6 T. This anisotropic behavior of TQ(B) can be well explained by a two-sublattice mean-field calculation, which corroborates the AFQ ordered state below TQ. The entropy release at TQ is only 10% of R In 2 expected for the Γ3 doublet, suggesting possible interplay between the quadrupolar degrees of freedom and the superconductivity. [ABSTRACT FROM AUTHOR]

Published
2012
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