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The location of the liquidus in the low-pressure crystalline phase of SnI4 was determined utilizing in situ x-ray diffraction measurements under pressures up to approximately 3.5 GPa. The liquidus is not well fitted to a monotonically increasing curve such as Simon's equation, but breaks near 1.5 GPa and then becomes almost flat. The results are compared to those from molecular dynamics simulations. Ways to improve the model potential adopted in the simulations are discussed. [ABSTRACT FROM AUTHOR]

The location of the liquidus in the low-pressure crystalline phase of SnI4 was determined utilizing in situ x-ray diffraction measurements under pressures up to approximately 3.5 GPa. The liquidus is not well fitted to a monotonically increasing curve such as Simon's equation, but breaks near 1.5 GPa and then becomes almost flat. The results are compared to those from molecular dynamics simulations. Ways to improve the model potential adopted in the simulations are discussed. [ABSTRACT FROM AUTHOR]

Polycrystalline AgNd(WO[sub 4])[sub 2] has been prepared by a in solid-state reaction. X-ray diffraction measurements indicate that this compound crystallizes with a scheelite-type tetragonal structure. Absorption and emission spectra have been measured, using the technique of the crystal field parameters, to obtain the energy levels scheme for Nd[sup 3+] ions in the crystalline matrix. These data indicate the existence of a structural local disorder associated with a random distribution of the ions of Ag[sup +] and Nd[sup 3+]. The temperature variation of the paramagnetic susceptibility in the range from 2 to 300 K has been studied. The Van Vleck formula has been used to calculate the temperature variation of the paramagnetic susceptibility and it was compared with the experimental results. Particularly at low temperatures, satisfactory agreement has been obtained. © 2003 American Institute of Physics. [ABSTRACT FROM AUTHOR]

The magnetocaloric effect in single crystalline Nd0.5Sr0.5MnO3 (NSMO 0.5) is investigated by computing the field dependent entropy change (ΔS) and adiabatic temperature change (ΔTad). At the charge ordering temperature (TCO), the value of ΔSmax is found to be much higher than ΔSmax reported in polycrystalline samples. This “giant” entropy change is attributed to interplay (stronger in single crystals) among spin, charge, lattice, and orbital degrees of freedom resulting in a field induced transition at TCO. In contrast, the change in entropy associated with Curie temperature (TC) is very low. The direct measurements of the field induced temperature change (ΔT) are in agreement with the computed value of ΔS. The presence of short-range correlations with charge/orbital order (COO) above and below TC may be responsible for the suppression of the negative MCE at TC. A critical exponent analysis of the paramagnetic (PM) to ferromagnetic (FM) transition using magnetization data yields mean-field-like values, which is likely to be operative in inhomogeneous systems such as NSMO 0.5 with correlated COO clusters larger than lattice parameter. [ABSTRACT FROM AUTHOR]

The magnetocaloric effect in single crystalline Nd0.5Sr0.5MnO3 (NSMO 0.5) is investigated by computing the field dependent entropy change (ΔS) and adiabatic temperature change (ΔTad). At the charge ordering temperature (TCO), the value of ΔSmax is found to be much higher than ΔSmax reported in polycrystalline samples. This “giant” entropy change is attributed to interplay (stronger in single crystals) among spin, charge, lattice, and orbital degrees of freedom resulting in a field induced transition at TCO. In contrast, the change in entropy associated with Curie temperature (TC) is very low. The direct measurements of the field induced temperature change (ΔT) are in agreement with the computed value of ΔS. The presence of short-range correlations with charge/orbital order (COO) above and below TC may be responsible for the suppression of the negative MCE at TC. A critical exponent analysis of the paramagnetic (PM) to ferromagnetic (FM) transition using magnetization data yields mean-field-like values, which is likely to be operative in inhomogeneous systems such as NSMO 0.5 with correlated COO clusters larger than lattice parameter. [ABSTRACT FROM AUTHOR]

The piezoelectric properties of [001]c poled 0.94Pb(Zn1/3Nb2/3)O3–0.06PbTiO3 single crystals were greatly enhanced by controlling their domain configurations. Contrary to the interpretation of charged domain walls being the main contributor to the piezoelectric enhancement, we found that smaller domain size and more neutral domain walls were the main contributors for the piezoelectric enhancement of these multidomain crystals. The properties of 109° neutral domain walls in 0.94Pb(Zn1/3Nb2/3)O3–0.06PbTiO3 single crystals were extracted by using a piezoelectric domain wall model. [ABSTRACT FROM AUTHOR]

First-principles calculations of the atomic and electronic structure of crystalline CoFeB/MgO/CoFeB magnetic tunnel junctions (MTJs) are performed to understand the effect of B on spin-dependent transport in these junctions. The authors find that it is energetically favorable for B atoms to reside at the crystalline CoFeB/MgO interface rather than remain in the bulk of the crystalline CoFeB electrode. The presence of B at the interfaces is detrimental to tunneling magnetoresistance (TMR) because it significantly suppresses the majority-channel conductance through states of Δ1 symmetry. Preventing B segregation to the interfaces during annealing should result in an enhanced TMR in CoFeB/MgO/CoFeB MTJs. [ABSTRACT FROM AUTHOR]

Different types of waveguides and connections between them were fabricated in a three-dimensional (3D) layer-by-layer photonic crystal. The waveguides were formed by removing either a single rod or a series of rod fragments running in three mutually orthogonal directions. This provides the potential of forming a 3D network of waveguide channels with cross sectional dimensions on the order of one lattice constant. The propagation behavior of guided modes in these waveguide networks was probed using a network analyzer. High transmission efficiency (with loss below 0.5 dB) through various waveguide bends and networks with carefully designed geometries has been achieved. © 2004 American Institute of Physics. [ABSTRACT FROM AUTHOR]

We demonstrate the use of Raman spectroscopy with a multichannel detector to characterize the growth of PtSi on Si(100). The vibrational modes of surface silicide layers as thin as 10 Å and PtSi layers less than 40 Å thick buried under 140 Å of Pt have been observed without the need for any special sample geometry for signal enhancement. The Raman spectra can identify the silicide layer, estimate its thickness, and demonstrate its crystalline quality. This can be done on an arbitrary substrate, in air and without any special sample preparation. [ABSTRACT FROM AUTHOR]