| 1. |
- Alam, Aftab, et al.
(författare)
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Effect of disorder on the electronic properties of graphene : A theoretical approach
- 2012
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Ingår i: Physical Review B. Condensed Matter and Materials Physics. - 1098-0121 .- 1550-235X. ; 86:8, s. 085454-
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Tidskriftsartikel (refereegranskat)abstract
- In order to manipulate the properties of graphene, it is very important to understand the electronic structure in the presence of disorder. We investigate, within a tight-binding description, the effects of disorder in the on-site (diagonal disorder) term in the Hamiltonian as well as in the hopping integral (off-diagonal disorder) on the electronic dispersion and density of states by the augmented space recursion method. Extrinsic off-diagonal disorder is shown to have dramatic effects on the two-dimensional (2D) Dirac cone, including asymmetries in the band structures as well as the presence of discontinuous bands (because of resonances) in certain limits. Disorder-induced broadening, related to the scattering length (or lifetime) of Bloch electrons, is modified significantly with increasing strength of disorder. We propose that our methodology is suitable for the study of the effects of disorder in other 2D materials, such as a boron nitride monolayer.
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| 2. |
- Banerjee, Mitali, et al.
(författare)
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Magnetism in FeNiW disordered alloys : Experiment and theory
- 2010
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Ingår i: Journal of Magnetism and Magnetic Materials. - : Elsevier BV. - 0304-8853 .- 1873-4766. ; 322:21, s. 3558-3564
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Tidskriftsartikel (refereegranskat)abstract
- We report here an experimental study of magnetization of FeNiW alloys at different compositions. We have studied variation of magnetization with temperature (at low external fields) and magnetic field (at low temperatures). The alloy shows para to ferromagnetic transitions across the composition range. We do not find any indication of the spin-glass phase. We have supplemented the experimental work with theoretical analysis using the first-principles tight-binding linear muffin-tin orbitals based augmented space recursion method. Our theoretical estimates of magnetic moment and Curie temperatures agree well with experiment. Our mean-field phase analysis also does not indicate the possibility of a spin-glass.
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| 3. |
- Banerjee, Mitali, et al.
(författare)
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Magnetism in NiFeMo disordered alloys : Experiment and theory
- 2010
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Ingår i: Physica. B, Condensed matter. - : Elsevier BV. - 0921-4526 .- 1873-2135. ; 405:20, s. 4287-4293
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Tidskriftsartikel (refereegranskat)abstract
- In this communication we carry out experimental investigation of the behavior of magnetization with temperature and magnetic field of six samples at different compositions of the disordered ternary alloy NiFeMo. We analyze the data using a fist-principles density functional based electronic structure method and a mean-field phase diagram study.
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| 4. |
- Banerjee, Rudra, et al.
(författare)
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Fe3.3Ni83.2Mo13.5 : a likely candidate to show spin-glass behaviour at low temperatures
- 2011
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Ingår i: Journal of Physics. - : IOP Publishing. - 0953-8984 .- 1361-648X. ; 23:10, s. 106002-
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Tidskriftsartikel (refereegranskat)abstract
- Unlike other transition metals alloyed with a non-magnetic metal, alloys of Ni behave rather differently. This is because of the fragility of the local magnetic moment on Ni. NiMo and NiW do not show any spin-glass phase. However, addition of Fe can bolster the moment on Ni. We wish to study whether the alloy Fe3.3Ni83.2Mo13.5, chosen near a composition where mean-field estimates suggest there could be a spin-glass phase, shows such a phase or not.
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| 5. |
- Chowdhury, Suman, et al.
(författare)
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A real-space study of random extended defects in solids : Application to disordered Stone–Wales defects in graphene
- 2014
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Ingår i: Physica. E, Low-Dimensional systems and nanostructures. - : Elsevier BV. - 1386-9477 .- 1873-1759. ; 61:0, s. 191-197
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Tidskriftsartikel (refereegranskat)abstract
- Abstract We propose here a first-principles, parameter free, real space method for the study of disordered extended defects in solids. We shall illustrate the power of the technique with an application to graphene sheets with randomly placed Stone–Wales defects and shall examine the signature of such random defects on the density of states as a function of their concentration. The technique is general enough to be applied to a whole class of systems with lattice translational symmetry broken not only locally but by extended defects and defect clusters. The real space approach will allow us to distinguish signatures of specific defects and defect clusters.
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| 6. |
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| 7. |
- Ganguly, Shreemoyee, et al.
(författare)
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Augmented space recursion study of the effect of disorder on superconductivity
- 2009
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Ingår i: Physical Review B. Condensed Matter and Materials Physics. - 1098-0121 .- 1550-235X. ; 79:22
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Tidskriftsartikel (refereegranskat)abstract
- We present a real-space approach to study the effect of disorder on superconductivity. The method is based on augmented space formalism that goes beyond mean-field approximations for configuration averaging and effectively deals with the influence of configuration fluctuations of the neighborhood of an atom. In the regime of validity of Anderson's theorem our results for s- and d-wave dirty superconductors have excellent agreement with existing results. The formalism is extended and tested for random negative U Hubbard model. Having verified the reliability of our method we use it to study environment-dependent inhomogeneous randomness in disordered superconducting systems.
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| 8. |
- Ganguly, Shreemoyee, et al.
(författare)
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Magnetism in small bimetallic Mn-Co clusters
- 2008
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Ingår i: Physical Review B. Condensed Matter and Materials Physics. - 1098-0121 .- 1550-235X. ; 78:1, s. 014402-
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Tidskriftsartikel (refereegranskat)abstract
- Effects of alloying on the electronic and magnetic properties of MnxCoy (x+y=n=2-5, x=0-n) and Mn2Co11 nanoalloy clusters are investigated using the density-functional theory. Unlike the bulk alloy, the Co-rich clusters are found to be ferromagnetic and the magnetic moment increases with Mn concentration and is larger than the moment of pure Co-n clusters of same size. For a particular sized cluster the magnetic moment increases by 2 mu(B)/Mn-substitution, which is found to be independent of the size and composition. All these results are in good agreement with recent Stern-Gerlach experiments [Phys. Rev. B 75, 014401 (2007) and Phys. Rev. Lett. 98, 113401 (2007)]. Likewise in bulk MnxCo1-x alloy, the local Co moment decreases with increasing Mn concentration.
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| 9. |
- Ganguly, Shreemoyee, et al.
(författare)
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Unusual structure and magnetism in manganese oxide nanoclusters
- 2011
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Ingår i: Physical Review B. Condensed Matter and Materials Physics. - 1098-0121 .- 1550-235X. ; 83:2, s. 020411-
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Tidskriftsartikel (refereegranskat)abstract
- We report an unusual evolution of structure and magnetism in stoichiometric MnO clusters based on an extensive and unbiased search through the potential-energy surface within density functional theory. The smaller clusters, containing up to five MnO units, adopt two-dimensional structures; and regardless of the size of the cluster, magnetic coupling is found to be antiferromagnetic in contrast to previous theoretical findings. Predicted structure and magnetism are strikingly different from the magnetic core of Mn-based molecular magnets, whereas, they were previously argued to be similar. Both of these features are explained through the inherent electronic structures of the clusters.
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| 10. |
- Ghosh, Tanmoy, et al.
(författare)
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Effect of short range ordering on the magnetism in disordered Fe:Al alloy
- 2014
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Ingår i: Journal of Alloys and Compounds. - : Elsevier BV. - 0925-8388 .- 1873-4669. ; 613, s. 306-311
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Tidskriftsartikel (refereegranskat)abstract
- Magnetic behavior of equiatomic FeAl alloy is still not satisfactorily understood. In this work, we studied the magnetic properties of disordered FeAl alloy both experimentally and using first-principles theories and revisited the alloy system in perspective of the inhomogeneity present in the system. After obtaining magnetic exchange interactions from first-principles theories, we carried out Monte-Carlo simulations on special quasi-random structures (SQS) and compared the results with experimental measurements. We tried to understand the plethora of often differing results and explain them in terms of possible inhomogeneities in the system.
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