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11.
Vyaselev O Arai K Kobayashi K Yamazaki J Kodama K Takigawa M Hanawa M Hiroi Z 《Physical review letters》2002,89(1):017001
We report Cd nuclear magnetic resonance (NMR) and Re nuclear quadrupole resonance (NQR) studies on Cd(2)Re(2)O(7), the first superconductor among pyrochlore oxides (T(c) approximately 1 K). The Re NQR spectrum at zero magnetic field below 100 K rules out any magnetic or charge order. The spin-lattice relaxation rate below T(c) exhibits a pronounced coherence peak and follows the weak-coupling BCS theory with nearly isotropic energy gap. The results of Cd NMR point to a moderate ferromagnetic enhancement at high temperatures followed by a rapid decrease of the density of states below the structural transition temperature of 200 K. 相似文献
12.
Mori S Endo M Furukawa S Sunaoka M Nonaka H Ishii T Ikehira H 《Magnetic resonance imaging》2005,23(5):691-694
We developed a high radiation sensitive polymer gel by modifying the amounts of the gel components and the temperature for the gel preparation. We evaluated its relaxation time linearity against dose and compared the measured dose distribution with the calculated one. For the relaxation time-dose linearity, irradiations were carried out with a linear accelerator using 6 MV photons and doses ranging from 0-5.0 Gy. The relationship between dose and R(2) value (reciprocal of T(2) relaxation time) was measured and it had good linearity over a wide range (0.3-5 Gy). The measured dose distributions were in good agreement with calculated ones. Since the present gel has higher sensitivity and it is synthesized more easily at lower cost than conventional polymer gels, we expect to see improved three-dimensional (3D) dosimetry using it. 相似文献
13.
Low temperature magnetization measurements on the pyrochlore spin ice compound Dy2Ti2O7 reveal that the ice-rule breaking spin flip, appearing at H approximately 0.9 T applied parallel to the [111] direction, turns into a novel first-order transition for T<0.36 K which is most probably of a liquid-gas type. T-linear variation of the critical field observed down to 0.03 K suggests the unusual situation that the entropy release across the transition remains finite [approximately 0.5 (J/K) x mol-Dy] as T-->0, in accordance with a breaking of the macroscopic degeneracy in the intermediate "kagomé ice" state. 相似文献
14.
A. Ueda H. Ohta S. Okubo Z. Hiroi M. Okumura M. Takano 《Applied magnetic resonance》2000,19(3-4):399-402
Quasi-one-dimensional (1-D) cupric oxide Ca1?xCuO2 (x = 0.164) is the system with 25–40% hole-doped edge-sharing CuO2 chains. However, the holes are almost localized in Ca1?xCuO2 and its magnetic susceptibility with a peak at 30 K was explained by the model considering both 1-D antiferromagnetic chains and spin dimers (Z. Hiroi, M. Okumura, Y. Nabeshima, T. Yamada, M. Takano: J. Phys. Soc. Jpn.69, 1824, 2000). To clarify the magnetic nature of Ca1?xCuO2, we performed submillimeter-wave electron spin resonance (ESR) measurements on a powder sample of Ca0.83?6CuO2. The resonance above 12 K showed typical powder ESR of Cu2+ and theg-values were determined to be g∥= 2.33 and g⊥ = 2.06 from the analysis. The resonance below 12 K changed completely from ESR. The frequency-field relation of ESR at 1.8 K clearly showed the easy-axis type antiferromagnetic resonance. 相似文献
15.
A. N. Vasil’ev O. L. Ignatchik A. N. Sokolov Z. Hiroi M. Isobe Y. Ueda 《JETP Letters》2003,78(9):551-554
Formation of a long-range magnetic order is observed at low temperatures in NaCrSi2O6 and NaCrGe2O6 quasi-one-dimensional metal oxide compounds with a pyroxene structure. The first of these compounds, NaCrSi2O6, is an antiferromagnet with the Néel temperature T N =3 K, while the second, NaCrGe2O6, is a ferromagnet with the Curie temperature T C =6 K. From the measurements of magnetization and specific heat of these compounds, the main parameters of their magnetic subsystems are determined. In NaCrSi2O6, a spin-flip transition is observed. A change in the type of magnetic order that accompanies the replacement of Si by Ge can be attributed to a change in the parameters of the competing direct antiferromagnetic Cr-Cr and indirect ferromagnetic Cr-O-Cr interactions in isolated chains of CrO6 octahedra. 相似文献
16.
Toru Tatsumi Ken-ichi Aketagawa Masayuki Hiroi Junro Sakai 《Journal of Crystal Growth》1992,120(1-4):275-278
The conditions under which selective epitaxial growth (SEG) is achieved in UHV-CVD with Si2H6 are determined by the amount of Si2H6 molecules being supplied, and there is a critical gas supply amount (Fc) beyond which SEG will break down and lose its selectivity. The value of Fc is itself determined by two factors, growth temperature and the material used for masking, i.e. SiO2, Si3N4. We found that this limiting factor of Fc was increased through the addition of a small amount of Cl2, and that after such addition, the resulting decrease in growth rate is minimal. 相似文献
17.
18.
Oxide heterojunctions made of p-type La0.8Sr0.2MnO3 (LSMO) and niobium-doped n-type SrTiO3 (STO:Nb) have been fabricated by the pulsed laser deposition (PLD) technique and characterized under UV light irradiation by measuring the current-voltage, photovoltaic properties and the junction capacitance. It is shown that the heterojunctions work as an efficient UV photodiode, in which photogenerated holes in the STO:Nb substrate are injected to the LSMO film. The maximum surface hole density Q/e and external quantum efficiency γ are estimated to be 8.3×1012 cm−2 and 11% at room temperature, respectively. They are improved significantly in a p-i-n junction of LSMO/STO/STO:Nb, where Q/e and γ are 3.0×1013 cm−2 and 27%, respectively. 相似文献
19.
20.
Frost heave in He 总被引:1,自引:0,他引:1
Frost heave occurs in various phenomena in natural environment. It has been studied in helium on porous glasses under perfect ice-segregation condition. The maximum frost heave pressure was investigated for various conditions and was in good agreement with the thermodynamical prediction. The dynamical properties of frost heave are discussed and some of the preliminary results of the growth rate measurement are presented. 相似文献