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Electrical conditioning properties and dielectric behavior of CaCu3Ti4O12 (CCTO) were investigated. A reversible current-voltage characteristic relaxation effect together with a corresponding dielectric relaxation was found in this material. A trap state model which combines a monopole and dipole relaxation was proposed to be the key element to explain the reported huge permittivity in CCTO. The work also supports the extrinsic origin of the giant dielectric constant. [ABSTRACT FROM AUTHOR]

Using first-principles density functional theory and nonequilibrium Green’s function formalism, we investigate the effect of the indices of crystal plane of electrodes on the electronic transport properties of molecular devices by taking C20 fullerene molecule as conductor component and semi-infinite Au(111)/(100) as electrodes. The results show that the transport behaviors through molecular devices are closely related to the crystallographic orientation of electrodes. Negative differential resistance (NDR) in the current-voltage curve can be observed for the Au(100) electrode case but cannot be observed for the Au(111) case. A mechanism for the NDR phenomenon is proposed. [ABSTRACT FROM AUTHOR]

The effect of combined Cu and Ti additions on the magnetic properties and phase transformation behavior of Nd[sub 8]Fe[sub 86]B[sub 6] nanocomposites prepared by melt spinning have been investigated. For pure ternary Nd[sub 8]Fe[sub 86]B[sub 6] ribbons, the α-Fe phase precipitates directly from amorphous phase and its grains grow quickly during crystallization. But for Nd[sub 8]Fe[sub 86]B[sub 6] ribbons with a combined addition of Cu and Ti, the crystallization temperature is increased by about 30 °C and a metastable hexagonal phase with a TbCu[sub 7]-type structure is formed prior to the α-Fe and Nd[sub 2]Fe[sub 14]B phase. When the annealing temperature is increased, a metastable 1:7 phase is decomposed into the α-Fe and Nd[sub 2]Fe[sub 14]B phase. At the same time, the growth of α-Fe grains is suppressed and the microstructure becomes more uniform. When the content of Cu reaches 1.0 at. % and that of Ti reaches 0.5 at. %, the optimal magnetic properties [sub i]H[sub c] = 4.8 kOe, σ[sub r] = 110 emu/g, (BH)[sub max] = 15 MGOe were obtained after annealing at the temperature of 650 °C for 8 min. So, a combined addition of Cu and Ti is very effective in improving the magnetic properties and reducing grain size and, in particular, the size of α-Fe grains. [ABSTRACT FROM AUTHOR]

Recently, the magnetocaloric effect (MCE) of Ni-Mn-based Heusler alloys has attracted more attention due to its metamagnetic shape-memory effect. However, most MCE investigations focused on the bulk alloys developed at high magnetic field (>2 T). In this paper, by employing the melt-spinning technique, a large MCE at low magnetic field was found in a ribbon of Ni50-xCoxMn35In15. The magnetic entropy change ΔS reaches the maximum value of 5.35 J/kg K at 1 T field in the Ni49CoMn35In15 ribbon near room temperature, and its corresponding temperature span arrives 24 K. The refrigerant capacity is enhanced with the increase of the Co substitution. Such a large MCE at low magnetic field in the Ni50-x CoxMn35In15 ribbon with a wide temperature range provides a potential candidate for room temperature magnetic refrigeration. [ABSTRACT FROM AUTHOR]

Electrical conditioning properties and dielectric behavior of CaCu3Ti4O12 (CCTO) were investigated. A reversible current-voltage characteristic relaxation effect together with a corresponding dielectric relaxation was found in this material. A trap state model which combines a monopole and dipole relaxation was proposed to be the key element to explain the reported huge permittivity in CCTO. The work also supports the extrinsic origin of the giant dielectric constant. [ABSTRACT FROM AUTHOR]