218,940 research outputs found
Low-temperature-dependent growth of titanium dioxide nanorod arrays in an improved aqueous chemical growth method for photoelectrochemical ultraviolet sensing
The growth of titanium dioxide nanorod arrays (TNAs) in aqueous solutions containing titanium butoxide and hydrochloric acid can be controlled by regulating the temperature from 115 to 150 °C as an adjustable physical parameter. The transparent colloidal solution of titanates is clouded on the basic growth of TNAs when heated at a certain temperature using an improved aqueous chemical growth method in a clamped Schott bottle. The structural, optical and electrical properties of grown TNAs films were thoroughly investigated and discussed. The distinct and high-intensity peaks observed in the X-ray diffraction pattern and Raman spectra of the grown TNAs show the rutile phase with high crystal quality. The crystallite size, diameter size, and thickness of TNAs decrease with decreasing growth temperature. The prepared TNAs were used to detect 365 nm ultraviolet (UV) photon energy (750 µW/cm2) in a photoelectrochemical cell structure with a maximum photocurrent of 26.31 µA and minimum photocurrent of 3.48 µA recorded for TNAs grown at 150 °C and 115 °C, respectively. The size, structural properties, charge transfer resistance, and electron lifetime play a key role in determining the UV sensing characteristics of the TNAs. Results show that TNAs are very promising in fabricating a UV sensor with a high response at 0 V bias even at a low growth temperature of 115 °C
Temperature-dependent Ginzburg-Landau parameter
Taking into account both the orbital and the paramagnetic depairing effects
we derive a simple analytic formula for the temperature dependence of the
Ginzburg-Landau parameter valid in vicinity of field dependent critical
temperature in a type-II superconductor.Comment: 3 pages, no figure
Torque magnetometry study of the spin reorientation transition and temperature-dependent magnetocrystalline anisotropy in NdCo5
We present the results of torque magnetometry and magnetic susceptibility measurements to study in detail the spin reorientation transition (SRT) and magnetic anisotropy in the permanent magnet NdCo5. We further show simulations of the measurements using first-principles calculations based on density-functional theory and the disordered local moment picture of magnetism at finite temperatures. The good agreement between theory and experimental data leads to a detailed description of the physics underpinning the SRT. In particular we are able to resolve the magnetization of, and to reveal a canting between, the Nd and Co sublattices. The torque measurements carried out in the ac and ab planes near the easy direction allow us to estimate the anisotropy constants, K 1, K 2 and K 4 and their temperature dependences. Torque curves, τ(γ) recorded by varying the direction of a constant magnetic field in the crystallographic ac plane show a reversal in the polarity as the temperature is changed across the SRT (240 < T < 285 K). Within this domain, τ(γ) exhibits unusual features different to those observed above and below the transition. The single crystals of NdCo5 were grown using the optical floating zone technique
Temperature dependent correlations in covalent insulators
Motivated by the peculiar behavior of FeSi and FeSb2 we study the effect of
local electronic correlations on magnetic, transport and optical properties in
a specific type of band insulator, namely a covalent insulator. Investigating a
minimum model of covalent insulator within a single-site dynamical mean-field
approximation we are able to obtain the crossover from low temperature
non-magnetic insulator to high-temperature paramagnetic metal with parameters
realistic for FeSi and FeSb2 systems. Our results show that the behavior of
FeSi does not imply microscopic description in terms of Kondo insulator
(periodic Anderson model) as can be often found in the literature, but in fact
reflects generic properties of a broader class of materials.Comment: 4 pages, 4 figure
Temperature-dependent proximity magnetism in Pt
We experimentally demonstrate the existence of magnetic coupling between two
ferromagnets separated by a thin Pt layer. The coupling remains ferromagnetic
regardless of the Pt thickness, and exhibits a significant dependence on
temperature. Therefore, it cannot be explained by the established mechanisms of
magnetic coupling across nonmagnetic spacers. We show that the experimental
results are consistent with the presence of magnetism induced in Pt in
proximity to ferromagnets, in direct analogy to the well-known proximity
effects in superconductivity.Comment: 4 pages, 3 figure
Temperature-Dependent Macromodels of Digital Device
This paper addresses the development of a temperature-dependent parametric macromodel for the output ports of a digital IC. The model parameters are estimated from port transient voltage and current waveforms by means of a simple and efficient procedure. The obtained models are implemented as SPICE subcircuits. They perform at an accuracy and efficiency level suitable for system-level SI and EMC simulation
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