Spin-Seebeck effects in Ni81Fe19/Pt films

The spin-Seebeck effect (SSE) converts a heat current into a spin current, a flow of spin angular momentum, and spin voltage, the driving force for nonequilibrium spin currents, in a ferromagnetic metal. In this study, the SSE in a ferromagnetic Ni₈₁Fe₁₉ film has been investigated by means of the inverse spin-Hall effect (ISHE) in a Pt film at room temperature. The experimental results measured in the Ni₈₁Fe₁₉/Pt system show that the sign of the thermally induced spin voltage is reversed between the higher- and lower-temperature ends of the Ni₈₁Fe₁₉ film. The ISHE in the Pt film allows us to detect the SSE signal with high sensitivity and to separate it from extrinsic thermoelectric effects.     

Crystal growth of InN by MOCVD with electric field along the c-axis

We report on physical properties of InN grown by metalorganic chemical vapor deposition (MOCVD) with electric field applied along the c-axis. The electric field is applied continuously from the growth of the low temperature InN buffer layer to the procedure of cooling down to room temperature. As a result, the crystal morphology degrades, c-lattice constant elongates by 0.12% at ±1 kV/cm, Hall mobility decreases, and the phonon vibration along the c-axis broadens, which suggests that the physical properties of InN can be controlled by the electric field applied along the c-axis during the crystal growth.     

Emission of nuclear quadrupole resonance from polycrystalline hexamethylenetetramine

The angular dependence of the nuclear quadrupole resonance (NQR) signal intensity emitted from polycrystalline hexamethylenetetramine has been analytically investigated for all directions for non-contact detection of chemicals by nuclear quadrupole resonance. The field pattern of the NQR signal from a column sample was measured. The emitted patterns were the same as that from a united single magnetic dipole, which fitted well to the estimation based on quadrupole principle axis system. This result is helpful to design an antenna for NQR remote detection.     

First-order transition in a 2D classical XY-model using microcanonical Monte Carlo simulations

We have simulated two-dimensional classical XY-model in a microcanonical ensemble using the Monte Carlo technique. Simulations were carried out on a square lattice having 25, 100 or 900-spins with periodic boundary conditions. The nearest neighbour interaction potential was taken to beV(θ)=2J[1−cos¹⁰⁰(θ/2)]. The system energy, mean square magnetization and vortex-density were calculated as functions of temperature. A sudden change in the system energy, vortex density and mean square magnetization was observed at the first-order transition which is associated with this choice of the nearest neighbour interaction potential. The transition temperature increases with decrease in the system size. It is found that the creation of a vortex-antivortex pair costs more energy during the first-order transition than the energy associated with a tightly bound vortex-antivortex pair.     

Coupling reactions of aryl and heteroaryl halides with a trimethylsilylethynylpyrazine

By the coupling reactions of trimethylsilylacetylene and 2-chloro-3,6-diisobutylpyrazine, 3,6-diisobutyl-2-trimethylsilylethynylpyrazine or 1,2-bis(3,6-diisobutylpyrazin-2-yl)acetylene was obtained, depending on the solvent used. The former substance coupled with various aryl and heteroaryl halides to give 1-aryl-2-pyrazin-ylacetylenes.     

The Diameters of Some Transition Graphs Constructed from Hamilton Cycles

 A complete undirected graph of order n has Hamilton cycles. We consider the diameter of a transition graph whose vertices correspond to those Hamilton cycles and any of two vertices are adjacent if and only if the corresponding Hamilton cycles can be transformed each other by exchanging two edges. Moreover, we consider several transition graphs related to it. Received: November 4, 1999 Final version received: August 28, 2000     

Polynomial invariants of graphs II

Negami and Kawagoe has already defined a polynomial associated with each graphG as what discriminates graphs more finely than the polynomialf(G) defined by Negami and the Tutte polynomial. In this paper, we shall show that the polynomial includes potentially the generating function counting the independent sets and the degree sequence of a graphG, which cannot be recognized fromf(G) in general, and discuss on of treesT with observations by computer experiments.