Ferroelectric polarization flop in a frustrated magnet MnWO4_4 induced by magnetic fields

The relationship between magnetic order and ferroelectric properties has been investigated for MnWO$_4$ with long-wavelength magnetic structure. Spontaneous electric polarization is observed in an elliptical spiral spin phase. The magnetic-field dependence of electric polarization indicates that the noncollinear spin configuration plays a key role for the appearance of ferroelectric phase. An electric polarization flop from the b direction to the a direction has been observed when a magnetic field above 10T is applied along the b axis. This result demonstrates that an electric polarization flop can be induced by a magnetic field in a simple system without rare-earth f-moments.Comment: 9 pages, 4 figure

Hall effect of quasi-hole gas in organic single-crystal transistors

Hall effect is detected in organic field-effect transistors, using appropriately shaped rubrene (C42H28) single crystals. It turned out that inverse Hall coefficient, having a positive sign, is close to the amount of electric-field induced charge upon the hole accumulation. The presence of the normal Hall effect means that the electromagnetic character of the surface charge is not of hopping carriers but resembles that of a two-dimensional hole-gas system

Research and Development in Foreign Affiliates: Evidence from Japanese Firms

This paper analyzes the determinants of the R&D intensity of 434 foreign affiliates, drawing on MITI''s benchmark survey of Japanese multinational firms in 1993. Acquired affiliates are responsible for more than half of overseas R&D expenditure and have significantly higher R&D intensities than wholly and majority owned greenfield affiliates. Non-majority owned joint ventures are R&D intensive in case the investing firm lacks substantial R&D capabilities in Japan. In contrast, R&D intensive Japanese parent firms prefer controlled modes of overseas R&D investment. Support is also found for an incremental growth pattern of foreign R&D operations as a function of cumulative learning. This learning is affiliate-specific rather than firm-wide and applies to greenfield affiliates but not to acquired affiliates. The results provide evidence that Japanese multinational firms, as ‘latecomers’ in the establishment of overseas R&D networks, have often made use of acquisitions and collaborative ventures to gain access to overseas technology and to establish overseas R&D capabilities at a faster pace.research and development ;

Low-energy excitations in electron-doped metal phthalocyanine from NMR in Li0.5_{0.5}MnPc

$^7$Li and $^1$H NMR and magnetization measurements in \lpc (Pc$\equiv$C$_{32}$H$_{16}$N$_8$), recently proposed as a strongly correlated metal, are presented. Two different low-frequency dynamics are evidenced. The first one, probed by $^1$H nuclei gives rise to a slowly relaxing magnetization at low temperature and is associated with the freezing of MnPc $S=3/2$ spins. This dynamic is similar to the one observed in pristine $\beta$-MnPc and originates from Li depleted chain segments. The second one, evidenced by $^7$Li spin-lattice relaxation rate, is associated with the hopping of the electrons along Li-rich chains. The characteristic correlation times for the two dynamics are derived and the role of disorder is briefly discussed.Comment: 7 two-columns pages, 11 figure

Microscopic Mechanism for Staggered Scalar Order in PrFe4P12

A microscopic model is proposed for the scalar order in PrFe4P12 where f2 crystalline electric field (CEF) singlet and triplet states interact with two conduction bands. By combining the dynamical mean-field theory and the continuous-time quantum Monte Carlo, we obtain an electronic order with staggered Kondo and CEF singlets with the total conduction number being unity per site. The ground state becomes semimetallic provided that the two conduction bands have different occupation numbers. This model naturally explains experimentally observed properties in the ordered phase of PrFe4P12 such as the scalar order parameter, temperature dependence of the resistivity, field-induced staggered moment, and inelastic features in neutron scattering. The Kondo effect plays an essential role for ordering, in strong contrast with ordinary magnetic orders by the RKKY interaction.Comment: 4 pages, 4figure