We present a comprehensive series of electrical transport ͑conductivity, magnetoresistance, and Hall effect͒, thermodynamic ͑specific heat, magnetic susceptibility, and magnetization͒, and optical ͑reflectivity͒ measurements in varying temperature ranges between 0.05 and 330 K on high-quality FeSi single crystals grown by vapor transport. The entire set of data can consistently be described with the usual relations for a ͑compensated n type͒ semiconductor if an unconventional band structure is assumed. Compared to the results of mean-field band-structure calculations, the height of the peaks in the total density of states around the energy gap is considerably enhanced, implying enhanced effective masses. Most likely correlation effects are the source of these features. At very low temperatures we encounter metallic behavior. A low concentration of correlated itinerant charge carriers coexists with interacting magnetic moments. ͓S0163-1829͑97͒05043-1͔

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In this paper we present a review of high-gas-pressure single crystal growth studies of YBa2Cu4O8 and Y2Ba4Cu7O15-x performed in oxygen pressure up to 3000 bar and Hg1-xMxBa2Can-1CunO2n+2+ (M = Pb, Re; n = 1-7) compounds in argon pressure up 11 000 bar at temperature up to 1200 °C. Chain compounds A1-xCuO2 (A = Sr, Ca, Ba) have been synthesized at high oxygen pressure up to 2000 bar. High-pressure phase diagram studies of the investigated systems are also discussed. Structure analyses of Y2Ba4CunO2n+x (n = 6-8), Hg1-xMxBa2Can-1CunO2n+2+ (M = Pb, Re; n = 1-8), Sr0.73CuO2 and (Sr,Ca)4Cu6O10 single crystals have been performed. The effects of substitutions and trends in bondlengths are discussed. The vortex state properties of HgBa2Ca2Cu3O8+ and YBa2Cu4O8 single crystals are compared. For Hg-based compounds, the influence of oxygen content, chemical substitutions and radiation defects on vortex pinning were determined. The quasi-one-dimensional cuprates Ca0.83CuO2 and Sr0.73CuO2 show an antiferromagnetically ordered state of long-range 3D character at T < 10 K. The spin dynamics of Sr0.73CuO2, measured by inelastic neutron scattering, indicate that this ordered state coexists with a dimerized singlet ground state.

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Organic thin films with non-centrosymmetric ordering of dipoles are very attractive as waveguides for nonlinear optic and electro-optic applications. [1,2] High electric field poling or self-assembly has been widely used to align dipolar molecules perpendicular to the film surface. [2] However, only a few examples of in-plane alignment of dipolar molecules have been described, including epitaxy on a lattice-matched organic substrate surface, [3,4] in-plane poling, [5] and Langmuir±Blodgett film deposition. [6,7] Based on a new type of nonlinear optical material, we have demonstrated, to our knowledge for the first time, that the dipolar molecules in an organic thin film can be in-situ aligned in any desired direction within the film plane by organic molecular beam deposition (OMBD) at oblique incidence. [8] This one-component, relatively fast (5 nm min ±1 ), OMBD based, and easily controlled thin film growth technique provides a new tool for the production of organic thin films with an in-plane directional order for second-order nonlinear optics (NLO) and electro-optics.Growth of organic thin films by OMBD (Fig. 1A) in ultrahigh vacuum (UHV) has many advantages over solution-based techniques, [9,10] such as greatly reduced contamination in the UHV environment, in-situ growth monitoring, high density of chromophores, and reasonably high growth rate. In addition, mask-defined microstructures such as strip waveguides, and integrated hetero-layer structures, like light emitting diode (LED) devices, [8,11] can be fabricated by OMBD. Despite these advantages, OMBD is still much less developed as compared to solution-based techniques for the preparation of second-order NLO films. The main obstacle lies within the materials.

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