We studied the phase stability in pseudobinary (Ni1−xPtx)3Al alloys using a combination of first-principles calculations, a cluster expansion technique, and Monte Carlo simulations. Our ground state search yields L10 ...
We studied the phase stability in pseudobinary (Ni1−xPtx)3Al alloys using a combination of first-principles calculations, a cluster expansion technique, and Monte Carlo simulations. Our ground state search yields L10 Ni2PtAl and L10 NiPt2Al as the two stable ground state structures, and the latter has been observed experimentally. The calculated c∕a ratio of L10 NiPt2Al is also in good agreement with experiments. By performing Monte Carlo simulations, the order-disorder transition temperatures of L10 Ni2PtAl and L10 NiPt2Al were predicted to be ∼915K and ∼1275K, respectively. The mixing enthalpies of random pseudobinary L12 (Ni1−xPtx)3Al alloys were also predicted using our cluster expansion, and the results agree well with direct first-principles calculations on Special Quasirandom Structures (SQS’s) for L12 alloys developed in the present study.
Inelastic neutron scattering techniques have been used to measure the phonon dispersion curves of bcc Fe1−xGax (x=10.8, 13.3, 16.0, 22.5) alloys as a function of Ga concentration. The phonon frequencies of every branc...
Inelastic neutron scattering techniques have been used to measure the phonon dispersion curves of bcc Fe1−xGax (x=10.8, 13.3, 16.0, 22.5) alloys as a function of Ga concentration. The phonon frequencies of every branch were found to decrease significantly with increasing Ga concentration. The softening was most pronounced for the T2[ξξ0] branch and, to a lesser extent, the L[ξξξ] branch in the vicinity of ξ=23. The concentration dependence of the shear elastic constant C′=1∕2(C11−C12), calculated from the slope of the T2[ξξ0] branch, was found to agree with the results of sound velocity measurements. For the higher concentration sample measured, 22.5 at. % Ga, new branches appeared, an effect associated with the increase in the number of atoms per unit cell.
Understanding the effect of Mn substitution for Fe in Co ferrite presents a challenge because there are three different transition-metal ions distributed among two distinct crystallographic and magnetic sublattices wi...
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Enhancement of light extraction in GaN light-emitting diodes (LEDs) employing omnidirectional reflectors (ODRs) is presented. The ODR consists of GaN, ITO nanorod low-refractive-index layer, and an Ag layer. An array ...
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Enhancement of light extraction in GaN light-emitting diodes (LEDs) employing omnidirectional reflectors (ODRs) is presented. The ODR consists of GaN, ITO nanorod low-refractive-index layer, and an Ag layer. An array of ITO nanorods is deposited by oblique-angle deposition using e-beam evaporation. The refractive index of the ITO nanorods is 1.34 at 461 nm, significantly lower that that of dense ITO, which is n = 2.06 at 461 nm. It is experimentally shown that the GaN LED with GaN/ITO nanorods/Ag ODR show much better electrical properties and higher light-extraction efficiency than LEDs with Ag contact. This is attributed to enhanced reflectivity of the ODR by using an ITO low-refractive-index layer with high transparency, high conductivity, and low refractive index.
We examine resonant interactions of optical pulses with nanostructured materials in the case of the electric field interacting with plasmonic oscillations in metallic nanospheres and double resonance including the mag...
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We measured the magnetic properties and heat capacity of three DyAl2 single crystals with the magnetic field oriented along the three principal crystallographic directions: [100], [110], and [111]. The isothermal entr...
We measured the magnetic properties and heat capacity of three DyAl2 single crystals with the magnetic field oriented along the three principal crystallographic directions: [100], [110], and [111]. The isothermal entropy change versus temperature curves were obtained from heat capacity and magnetization data for these directions. The experimental results were successfully explained by a mean field model that includes spin reorientation, exchange interactions, and crystalline electric field effects. The anomalous magnetocaloric effect along the [111] direction predicted by theory was confirmed experimentally.
Laser cooling in thulium- and ytterbium-doped BaY2F8 crystals is observed. We investigate the potential of this crystalline host for all-solid-state cryocooler applications as compared to those based on rare-earth dop...
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This manuscript presents the development of a low intensity magnetic field transducer, based on the Giant Magnetoimpedance (GMI) effect, to be used for biomedical applications. The GMI effect is a characteristic of so...
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ISBN:
(纸本)9781622766970
This manuscript presents the development of a low intensity magnetic field transducer, based on the Giant Magnetoimpedance (GMI) effect, to be used for biomedical applications. The GMI effect is a characteristic of some ferromagnetic materials, due to which it is observed a large variation of the material impedance due to external dc magnetic fields. We describe the effect, the transducer configuration, the electronic circuits and the preliminary results obtained so far. A sensitivity comparable to a fluxgate probe has already been obtained, and the theoretical calculations indicate the possibility of further enhancing this figure of merit.
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