STRUCTURAL, MAGNETIC AND ELECTRONIC PROPERTIES OF THE Sr2CoNbO6 COMPLEX PEROVSKITE

2013 ◽  
Vol 27 (28) ◽  
pp. 1350171 ◽  
Author(s):  
J. M. RENDÓN RAMÍREZ ◽  
O. A. ALMANZA M. ◽  
R. CARDONA ◽  
D. A. LANDÍNEZ TÉLLEZ ◽  
J. ROA-ROJAS
Keyword(s):  
Electronic Properties ◽  
Structure Prediction ◽  
Density Functional ◽  
Energy Gap ◽  
Magnetic Ordering ◽  
Double Perovskite ◽  
Rietveld Analysis ◽  
Lattice Parameters ◽  
Blocking Temperature ◽  
Generalized Gradient

We report a study of crystallographic parameters of the Sr 2 CoNbO 6 double perovskite obtained from Rietveld analysis of X-ray diffraction data and electronic properties predictions using the density functional theory (DFT). The Sr 2 CoNbO 6 material was prepared by the citrate precursor method. Diffraction analysis reveal that this material crystallizes in a structure which is tetragonal with lattice parameters a = 5.5960(3) Å and c = 7.9881(1) Å (space group I4/m). The density of states of Sr 2 CoNbO 6 tetragonal distorted structure was calculated using DFT within the generalized gradient approximation. Results predict the semiconductor characteristics of this material which is majority due to the 3d- Co orbital with a energy gap of 0.2 eV. Structural lattice parameters obtained from the Rietveld refinement present a matching of 97% with that obtained from the Structure Prediction Diagnostic Software and 98% with the theoretical DFT results. Measurements of magnetization as a function of temperature evidence the occurrence of a magnetic ordering transition at T = 220 K and a marked irreversibility with a blocking temperature of 250 K for applied fields up to 100 Oe, which disappears for higher fields. Electronic paramagnetic resonance experiments evidence that the valence Co 3+ is the most possible in the synthesized material.

FIRST PRINCIPLES STUDY OF ELECTRONIC STRUCTURE AND MAGNETIC PROPERTIES OF HALF-METALLIC FULL-HEUSLER ALLOYS Co2MnSi and Co2FeSi

2010 ◽  
Vol 24 (08) ◽  
pp. 967-978 ◽  
Author(s):  
JINGSHAN QI ◽  
HAILIN YU ◽  
XUEFAN JIANG ◽  
DANING SHI
Keyword(s):  
Magnetic Properties ◽  
Electronic Structure ◽  
Density Functional ◽  
Energy Gap ◽  
Magnetic Moments ◽  
Heusler Alloys ◽  
Lattice Parameters ◽  
Generalized Gradient ◽  
Half Metallicity ◽  
Half Metallic

We present a comprehensive investigation of the equilibrium structural, electronic and magnetic properties of C o2 MnSi and C o2 FeSi by density-functional theory (DFT) within the generalized gradient approximation (GGA) using the projected augmented wave (PAW) method. The on-site Coulomb interaction has also taken into account ( GGA +U) approach to unravel the correlation effects on the electronic structure. The change of the energy gap, "spin gap", Fermi energy level and magnetic moments with the lattice parameters is investigated. We found that the on-site correlation interaction in C o2 FeSi is stronger than in C o2 MnSi . So on-site electronic correlation is necessary for C o2 FeSi and the magnetic moments reproduce experimental results well by GGA +U. Further we also found that a moderate change of the lattice parameters does not change the half-metallic ferromagnet (HMF) behavior for both materials. Appearance of half-metallicity is consistent with the integral magnetic moments, which also agrees with the experiment measurements.

First-principles prediction of insulating antiferromagnet in ordered double-perovskite Ca2MnMoO6 compound

2017 ◽  
Vol 06 (04) ◽  
pp. 1750027 ◽  
Author(s):  
A. Djefal ◽  
S. Amari ◽  
K. O. Obodo ◽  
L. Beldi ◽  
H. Bendaoud ◽  
...  
Keyword(s):  
Magnetic Moment ◽  
Density Functional ◽  
Energy Gap ◽  
Double Perovskite ◽  
Ferromagnetic Phase ◽  
Full Potential ◽  
Generalized Gradient ◽  
Spin Configuration ◽  
Metallic Character ◽  
Conduction Bands

Using first-principle calculations within the framework of density functional theory (DFT), the full-potential linearized augmented plane-wave (FP-LAPW) method have been performed to investigate structural, electronic and magnetic properties of the Ca2MnMoO6 double perovskite. Different spin configurations (ferromagnetic (FM), ferrimagnetic (FiM), and anti-ferromagnetic AFM1, and AFM2) within both generalized gradient approximation (GGA) and [Formula: see text] (Hubbard Coulomb onsite correction) were considered. The value of the Hubbard−Coulomb [Formula: see text] parameter was varied in the range of [Formula: see text][Formula: see text]eV. The ground state is found to be AFM and insulating with the AFM1 state which is the most favorable. In the AFM1 spin configuration, Ca2MnMoO6 compound has a semiconductor nature, with the fully spin-polarized valence and conduction bands in the same spin channel. Within the [Formula: see text] approximation, the FM phase has a half-metallic character with a net magnetic moment of [Formula: see text] while in the anti-ferromagnetic phase it has an insulating character with zero net magnetic moment which was found at [Formula: see text][Formula: see text]eV. We found that in the AFM phase within the GGA approximation, a metallic character is obtained for Ca2MnMoO6 and also for [Formula: see text][Formula: see text]eV. In particular, for Hubbard [Formula: see text] of 3.6[Formula: see text]eV, a small energy gap of 0.20[Formula: see text]eV is observed. The main features shown by the density of states curves motivate further experimental exploration in the double perovskite Ca2MnMoO6 for spintronic applications.

scholarly journals Half-metallic Ferromagnetism in Non-magnetic Double Perovskite Oxides Sr2MSbO6 (M=Al, Ga) Doped with C and N.

2021 ◽  
Author(s):  
AMRANI Bouhalouane ◽  
Djilali BENDJEBBOUR ◽  
Tayeb SEDDIK ◽  
Mohamed Walid MOHAMED ◽  
driss khdoja
Keyword(s):  
Density Functional ◽  
Energy Gap ◽  
Double Perovskite ◽  
Perovskite Oxides ◽  
Full Potential ◽  
Double Perovskites ◽  
Generalized Gradient ◽  
Half Metallic ◽  
Impurity Bands ◽  
C And N

Abstract Double perovskite oxides have gained tremendous attention in material science and device technology due to their facile synthesis and exceptional physical properties. In this paper, we elucidate the origin of magnetization in non magnetic double perovskite oxides Sr2MSbO6 (M=Al, Ga) induced by non-magnetic 2p-impurities (C and N) substituted. The calculations were done within the full potential linearized augmented plane wave method (FP-LAPW) in the framework of the density functional theory (DFT). The exchange-correlation potential is evaluated using the generalized gradient approximation (GGA) of Perdew–Burke–Ernzerhof (PBE) and the modified Becke and Johnson (mBJ-GGA). Regarding structural properties of undoped double perovskites Sr2MSbO6 (M=Al, Ga), we found that the lattice constants and oxygen positions are in rational accord with the experimental results. Furthermore, both of the examined compounds are brittle in nature with isotropic character. For Sr2AlSbO6 we have got the values of energy gap equal to 1.9 eV and 3.7 eV within the GGA and the mBJ-GGA, respectively. However for Sr2GaSbO6 the values of energy gap obtained in GGA and mBJ-GGA are equal to 0.8 eV and 2.9 eV, respectively. Finally, spin-polarized calculations reveal that the doping C and N can lead to drastic changes in the magneto-electronic properties of the semiconducting Sr2MSbO6 matrix with the integer magnetic moment of 6.00 µB and exhibit half-metallic properties. The origin of ferromagnetism can be attributed to the spin–split impurity bands inside the energy gap of the semiconducting Sr2MSbO6 matrix. These results may help experimentalists in synthesizing new double perovskites for spintronic applications.

scholarly journals Improved electronic structure prediction of chalcopyrite semiconductors from a semilocal density functional based on Pauli kinetic energy enhancement factor

2021 ◽  
Author(s):  
Arghya Ghosh ◽  
Subrata Jana ◽  
Manish Niranjan ◽  
Sushant Kumar Behera ◽  
Lucian A. Constantin ◽  
...  
Keyword(s):  
Kinetic Energy ◽  
Electronic Properties ◽  
Structure Prediction ◽  
Enhancement Factor ◽  
Density Functional ◽  
Hybrid Methods ◽  
Computational Cost ◽  
Superior Performance ◽  
Generalized Gradient ◽  
Chalcopyrite Semiconductors

Abstract The correct treatment of d electrons is of prime importance in order to predict the electronic properties of the prototype chalcopyrite semiconductors. The effect of d states is linked with the anion displacement parameter u, which in turn influences the bandgap of these systems. Semilocal exchange-correlation functionals which yield good structural properties of semiconductors and insulators often fail to predict reasonable u because of the underestimation of the bandgaps arising from the strong interplay between d electrons. In the present study, we show that the meta-generalized gradient approximation (meta-GGA) obtained from the cuspless hydrogen density (MGGAC) [Phys. Rev. B 100, 155140 (2019)] performs in an improved manner in apprehending the key features of the electronic properties of chalcopyrites, and its bandgaps are comparative to that obtained using state-of-art hybrid methods. Moreover, the present assessment also shows the importance of the Pauli kinetic energy enhancement factor, α=(τ-τ<W>)/\τ<unif> in describing the d electrons in chalcopyrites. The present study strongly suggests that the MGGAC functional within semilocal approximations can be a better and preferred choice to study the chalcopyrites and other solid-state systems due to its superior performance and significantly low computational cost.

scholarly journals First-principle investigations of structural and electronic properties of TMAl (TM = Fe, Co, and Ni) transition metal aluminides

2015 ◽  
Vol 33 (2) ◽  
pp. 251-258
Author(s):  
Bendouma Doumi ◽  
Allel Mokaddem ◽  
Mustapha Ishak-Boushaki ◽  
Miloud Boutaleb ◽  
Abdelkader Tadjer
Keyword(s):  
Transition Metal ◽  
Electronic Properties ◽  
Density Functional ◽  
First Principle ◽  
Generalized Gradient ◽  
Metallic Behavior ◽  
Plane Wave Method ◽  
Structural And Electronic Properties ◽  
The Difference ◽  
Metal Aluminides

AbstractIn the present work, we have investigated the structural and electronic properties of TMAl (TM = Fe, Co, and Ni) transition metal aluminides in the B2 structure, using first-principle calculations of the density functional theory (DFT) based on the linearized augmented plane wave method (FP-LAPW) as implemented in the WIEN2k code, in which the energy of exchange and correlation are treated by the generalized gradient approximation (GGA), proposed in 1996 by Perdew, Burke and Ernzerhof (PBE). The ground state properties have been calculated and compared with other calculations, and the electronic structures of all FeAl, CoAl, and NiAl compounds exhibited a metallic behavior. It was depicted that the density of states is characterized by the large hybridization between the s-p (Al) and 3d (Fe, Co, and Ni) states, which creates the pseudogap in the region of anti-bonding states. Moreover, the band structures of FeAl, CoAl, and NiAl are similar to each other and the difference between them is in the energy level of each band relative to the Fermi level.

scholarly journals Análisis cristalográfico, morfológico, eléctrico, óptico y magnético del nuevo material Dy2BiFeO6

2018 ◽  
Vol 9 (1) ◽  
Author(s):  
Jairo Roa-Rojas
Keyword(s):  
Dielectric Constant ◽  
Energy Gap ◽  
Magnetic Hysteresis ◽  
Magnetic Ordering ◽  
Relative Dielectric Constant ◽  
Double Perovskite ◽  
Crystallographic Analysis ◽  
Weiss Temperature ◽  
Constant E ◽  
Diffraction Patterns

We report structural analysis, surface morphology, magnetic ordering, dielectric response, optical feature and the electronic structure of the Dy2BiFeO6 novel complex perovskite. The samples were produced by the standard solid-state reaction recipe. Crystallographic analysis was performed by Rietveld refinement of experimental X-ray diffraction patterns. Results show that this material crystallizes in a perovskite with orthorhombic structure, which corresponds to the Pnma (#62) space group. From the Curie-Weiss fitting on the curve of susceptibility as a function of temperature we establish that the ordering corresponds to a paramagnetic-antiferromagnetic transition, with a Weiss temperature q=-18,5 K, which is compatible with the behavior of the inverse of susceptibility as a function of temperature, and a Néel temperatura TN=50,8 K. The Curie constant allowed for us to obtain an effective magnetic moment of 15,7 mB. The result of magnetization as a function of the applied field, measured at T=50 K, shows a magnetic hysteresis behavior that corroborate the magnetic ordering present for this temperature value. Measurements of the dielectric constant as a function of applied frequencies at room temperature give as a result a high relative dielectric constant (e=780). The reflectance curve as a function of the wavelength reveals the typical behavior of a double perovskite-like material and permits to obtain the energy gap 2,74 eV, which is characteristic of a semiconductor material.

scholarly journals Structural and Electronic Properties of Orthorhombic Phase Bi2Se3 Based On First-Principles Study

2019 ◽  
Vol 16 (2) ◽  
pp. 77 ◽  
Author(s):  
Muhammad Zamir Mohyedin ◽  
Afiq Radzwan ◽  
Mohammad Fariz Mohamad Taib ◽  
Rosnah Zakaria ◽  
Nor Kartini Jaafar ◽  
...  
Keyword(s):  
Electronic Properties ◽  
First Principles ◽  
Density Functional ◽  
Local Density ◽  
Computer Code ◽  
First Principles Calculation ◽  
Generalized Gradient ◽  
Exchange Correlation ◽  
Percentage Difference ◽  
Structural And Electronic Properties

Bi2Se3 is one of the promising materials in thermoelectric devices and very useful out of environmental concern due to its efficiency to perform at room temperature. Based on the first-principles calculation of density functional theory (DFT) by using CASTEP computer code, structural and electronic properties of Bi2Se3 were investigated. The calculation is conducted within the exchange-correlation of local density approximation (LDA) and generalized gradient approximation within the revision of Perdew-Burke-Ernzerhof (GGA-PBE) functional. It was found that the results are consistent with previous works of theoretical study with small percentage difference. LDA exchange-correlation functional method is more accurate and have a better agreement than GGA-PBE to describe the structural properties of Bi2Se3 which consist of lattice parameters. LDA functional also shown more accurate electronic structure of Bi2Se3 that consist of band structure and density of states (DOS) which consistent with most previous theoretical works with small percentage difference. This study proves the reliability of CASTEP computer code and show LDA exchange-correlation functional is more accurate in describing the nature of Bi2Se3 compared to the other functionals.

scholarly journals TAO-DFT Study on the Electronic Properties of Diamond-Shaped Graphene Nanoflakes

Nanomaterials ◽  
2020 ◽  
Vol 10 (6) ◽  
pp. 1236 ◽  
Author(s):  
Hong-Jui Huang ◽  
Sonai Seenithurai ◽  
Jeng-Da Chai
Keyword(s):  
Electronic Properties ◽  
Density Functional ◽  
Energy Gap ◽  
Quantitative Measure ◽  
Smooth Transition ◽  
Von Neumann Entropy ◽  
Triplet Energy ◽  
Von Neumann ◽  
Graphene Nanoflakes ◽  
Radical Nature

At the nanoscale, it has been rather troublesome to properly explore the properties associated with electronic systems exhibiting a radical nature using traditional electronic structure methods. Graphene nanoflakes, which are graphene nanostructures of different shapes and sizes, are typical examples. Recently, TAO-DFT (i.e., thermally-assisted-occupation density functional theory) has been formulated to tackle such challenging problems. As a result, we adopt TAO-DFT to explore the electronic properties associated with diamond-shaped graphene nanoflakes with n = 2–15 benzenoid rings fused together at each side, designated as n-pyrenes (as they could be expanded from pyrene). For all the n values considered, n-pyrenes are ground-state singlets. With increasing the size of n-pyrene, the singlet-triplet energy gap, vertical ionization potential, and fundamental gap monotonically decrease, while the vertical electron affinity and symmetrized von Neumann entropy (which is a quantitative measure of radical nature) monotonically increase. When n increases, there is a smooth transition from the nonradical character of the smaller n-pyrenes to the increasing polyradical nature of the larger n-pyrenes. Furthermore, the latter is shown to be related to the increasing concentration of active orbitals on the zigzag edges of the larger n-pyrenes.

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