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Ferromagnetism and antiferromagnetism coexistence in SrRu 1-xMnxO3: Density functional calculation
, Article Journal of Solid State Chemistry ; Volume 184, Issue 3 , March , 2011 , Pages 536-545 ; 00224596 (ISSN) ; Fallahi, S ; Akhavan, M ; Sharif University of Technology
Abstract
We have calculated the electronic structure of SrRu1-xMn xO3 using the full potential linearized augmented plane wave method by LSDA and LSDAU. The antiparallel alignment between the Mn and Ru ions are consistent with the competition between ferromagnetism and antiferromagnetism in the low Mn-doped polycrystalline samples. This is in contrast to the appearance of quantum critical point and FM and AFM transitions in the single crystal measurement. Our results show that the discrepancy between different experimental phase diagrams is related to the conditions of sample preparation and also the difference between the degree of magnetic interactions between the Mn and Ru moments. The DOS and the...
Effect of electron correlation in Sr(Ca)Ru1-xCrxO3: Density functional calculation
, Article Journal of Solid State Chemistry ; Volume 183, Issue 7 , 2010 , Pages 1678-1690 ; 00224596 (ISSN) ; Akhavan, M ; Sharif University of Technology
2010
Abstract
We have investigated the electronic structure of Sr(Ca)Ru1-xCrxO3 using the full potential linearized augmented plane wave method by different approximation such as LSDA and LSDA+U. The LSDA calculation suggest that Cr4+-Ru4+ hybridization is responsible for the high Curie temperature TC in SrRu1-xCrxO3, but it cannot completely describe its physical behavior. Our LSDA+U DOS results for SrRu1-xCrxO3 clearly establishes renormalization of the intra-atomic exchange strength at the Ru sites, arising from the Cr-Ru hybridization. The antiferromagnetic coupling of Cr3+ with Ru4+,5+ lattice increases the screening, which is consistent with the low magnetic moment of the Ru ions. The more distorted...
Formulation of differential transfer matrix method in cylindrical geometry
, Article Proceedings of SPIE - The International Society for Optical Engineering, 25 January 2010 through 28 January 2010 ; Volume 7597 , January , 2010 ; 0277786X (ISSN) ; 9780819479938 (ISBN) ; Khorasani, S ; Rashidian, B ; Mohammadi, S ; Sharif University of Technology
2010
Abstract
Transfer and scattering matrix methods are widely in use for description of the propagation of waves in multilayered media. When the profile of refractive index is continuous, however, a modified formulation of transfer matrices does exist, which provides a complete analytical solution of the wave phenomena in such structures. Previously reported variations of the so-called Differential Transfer Matrix Method (DTMM) had been limited to Cartesian geometry where layered media form one-dimensional structures and plane waves are used as basis functions. In this work, we extend the formalism to cylindrical geometry with radial symmetry, in which Bessel functions need to be employed as basis...
Influence of asymmetry on the band structure of photonic crystals
, Article Proceedings of SPIE - The International Society for Optical Engineering, 26 January 2010 through 28 January 2010 ; Volume 7609 , January , 2010 ; 0277786X (ISSN) ; 9780819480057 (ISBN) ; Khorasani, S ; Sharif University of Technology
2010
Abstract
Computer calculation of photonic band structure for unit cells of various symmetry in the two-dimensional square lattice suggests that the bandgap calculated by traversing the ΓXM triangle in k-space is only reliable when the unit cell is C4v symmetric. For structures of lower symmetry, examining a two-dimensional subset of the first Brillouin zone will give smaller bandgaps
How T c can go above 100 K in the YBCO family
, Article European Physical Journal B ; Volume 73, Issue 1 , 2010 , Pages 79-83 ; 14346028 (ISSN) ; Akhavan, M ; Sharif University of Technology
2010
Abstract
We report the results of the electronic structure calculation of a newly discovered member of the YBCO high-T c family, i.e., Y 3Ba 5Cu 8O 18 (Y358) with T c>100, based on the full-potential linearized augmented plane waves method (FP-LAPW) of density functional theory in the generalized gradient approximation (GGA). The evolution of the number of hole carriers in different sites of the CuO 2 planes and CuO chains has been investigated in comparison with the other YBCO family members, i.e., Y123, Pr123, Y124, and Y247. The results suggest that pumping hole carriers out of the chains toward the planes enhances the transition temperature. The band structure calculations have been performed for...
Transmission-line model to design matching stage for light coupling into two-dimensional photonic crystals
, Article Optics Letters ; Volume 35, Issue 2 , 2010 , Pages 115-117 ; 01469592 (ISSN) ; Khavasi, A ; Mehrany, K ; Rashidian, B ; Sharif University of Technology
Abstract
The transmission-line analogy of the planar electromagnetic reflection problem is exploited to obtain a transmission-line model that can be used to design effective, robust, and wideband interference-based matching stages. The proposed model based on a new definition for a scalar impedance is obtained by using the reflection coefficient of the zeroth-order diffracted plane wave outside the photonic crystal. It is shown to be accurate for in-band applications, where the normalized frequency is low enough to ensure that the zeroth-order diffracted plane wave is the most important factor in determining the overall reflection. The frequency limitation of employing the proposed approach is...
In-plane and out-of-plane waves in nanoplates immersed in bidirectional magnetic fields
, Article Structural Engineering and Mechanics ; Volume 61, Issue 1 , 2017 , Pages 65-76 ; 12254568 (ISSN) ; Gharebaghi, S. A ; Mehri, B ; Sharif University of Technology
Techno Press
2017
Abstract
Prediction of the characteristics of both in-plane and out-of-plane elastic waves within conducting nanoplates in the presence of bidirectionally in-plane magnetic fields is of interest. Using Lorentz's formulas and nonlocal continuum theory of Eringen, the nonlocal elastic version of the equations of motion is obtained. The frequencies as well as the corresponding phase and group velocities pertinent to the in-plane and out-of-plane waves are analytically evaluated. The roles of the strength of in-plane magnetic field, wavenumber, wave direction, nanoplate's thickness, and small-scale parameter on characteristics of waves are discussed. The obtained results show that the in-plane...