Noriaki Kimura

Thermal expansion anomaly of UPt3 below 70mK

The thermal expansion of the single crystal of UPt3 has been measured at temperatures down to 1 mK by a capacitance dilatometer. We have first observed a large thermal expansion anomaly aroundTa=17 mK. It corresponds to the specific heat anomaly observed in 1992. Furthermore, the expansion coefficients depend onT−2 at the temperature aboveTa, andT2 at that belowTa respectively.

Oxidation of nitric oxide by atmospheric pressure plasma in a resonant plasma reactor

A novel non-equilibrium atmospheric-pressure-plasma generation system is proposed. The system discussed in this study is specifically designed for nitrogen oxide (NOx) gas treatment. A plasma is generated by a high-voltage radio-frequency (RF) electric field formed in the system that accumulates electromagnetic energy by resonance provided by a low-voltage power supply. With an input RF voltage of 100?200?V, a high voltage of 4k?8?kV at the same frequency can be formed on the powered electrode of the system under the resonance conditions. The plasma generator also serves as a plasma reactor, in which nitric oxide (NO) can be efficiently oxidized to form nitrogen dioxide (NO2) in the presence of oxygen (O2) at atmospheric pressure. It has been shown that, in terms of NO oxidation efficiency, the resonant plasma reactor proposed in this study is comparable or even superior to some of the previously proposed NO oxidation systems.

Fermi surface property of UPt3 studied by magnetoresistance and dHvA effect

Abstract We have studied the Fermi surface property from the transverse magnetoresistance and de Haas-van Alphen (dHvA) experiments in UPt 3 . These results have been discussed on the basis of the itinerant 5f band model.

Quantum cascade laser absorption spectroscopy with the amplitude-to-time conversion technique for atmospheric-pressure plasmas

The NO2 concentration, i.e., density, in a small plasma of a nitrogen oxide (NOx) treatment reactor has been measured by highly sensitive laser absorption spectroscopy. The absorption spectroscopy uses a single path of a quantum cascade laser beam passing through a plasma whose dimension is about 1u2009cm. The high sensitivity of spectroscopy is achieved by the amplitude-to-time conversion technique. Although the plasma reactor is designed to convert NO in the input gas to NO2, it has been demonstrated by this highly sensitive absorption spectroscopy that NO2 in a simulated exhaust gas that enters the reactor is decomposed by the plasma first and then NO2 is formed again, possibly more than it was decomposed, through a series of gas-phase reactions by the time the gas exits the reactor. The observation is consistent with that of an earlier study on NO decomposition by the same type of a plasma reactor [T. Yumii et al., J. Phys. D 46, 135202 (2013)], in which a high concentration of NO2 was observed at the exi...

Superconducting property of single crystal U6Fe

Abstract We have determined the lower and upper critical fields, H c1 and H c2 by measuring the DC magnetization, the AC susceptibility and the resistivity in fields for a superconductor U 6 Fe. The coherence length and the penetration depth are estimated as 50 and 2060 A, respectively.

195Pt Knight shift study of single crystal UPt3—evidence for odd-parity pairing—

The195Pt Knight shift of the high quality single crystal UPt3 measured down toT=28 mK have revealed no change acrossTc regardless of the applied field directions and of the superconducting multiphases. An estimation of the spin part from theT linear specific heat has ensured no variation of the dominant spin part of the measured Knight shift belowTc as well as its estimation by the subtraction of the Van Vleck part from theT dependence of the Knight shift in the highT region reported in the previous paper. It is reinforced that UPt3 is the odd-parity superconductor with equal spin pairing and the pinning of the order parameter does not take place, suggesting the spin-orbit coupling for the pairing interaction to be not so strong.

Ergodic behaviour of nonlinear hydromagnetic waves in a cold collisionless plasma

Nonlinear hydromagnetic waves propagating along a magnetic field in a cold collisionless plasma are investigated. A criterion for ergodicity of the waves is obtained using the usual method of analytical dynamics. According to this criterion, it is found that, if a parameter b 00 is a rational number, the wave is periodic, and that, if b 00 is an irrational number, the wave is ergodic. Therefore, the waves are almost always ergodic, i.e. the trajectory of the wave fills up a region in the phase plane of the magnetic field. On the other hand, periodic solutions can exist only with measure zero.

Spontaneous magnetization on the superconducting transition in UPt3

Theories predict that spontaneous magnetization occurs in the superconducting B phase in UPt3 because of broken time-reversal symmetry. The strength of the spontaneous magnetization depends on whether it comes from spin degeneracy or orbital degeneracy. We measured the internal field due to the spontaneous magnetization on the supercondicting transition to the B phase for a UPt3 sample in the magnetic fields very close to zero, using a SQUID magnetometer. The upper limit of the spontaneous internal field was 0.007 gauss. This result seems to favor the theory of the orbital degeneracy.