Two Dimensional Spin-Polarized Electron Gas at the Oxide Interfaces

The formation of a novel spin-polarized 2D electron gas at the LaMnO$_3$ monolayer embedded in SrMnO$_3$ is predicted from the first-principles density-functional calculations. The La (d) electrons become confined in the direction normal to the interface in the potential well of the La layer, serving as a positively-charged layer of electron donors. These electrons mediate a ferromagnetic alignment of the Mn t$_{2g}$ spins near the interface via the Anderson-Hasegawa double exchange and become, in turn, spin-polarized due to the internal magnetic fields of the Mn moments.Comment: 5 pages, 6 figure

Strain and Electric Field Modulation of the Electronic Structure of Bilayer Graphene

We study how the electronic structure of the bilayer graphene (BLG) is changed by electric field and strain from {\it ab initio} density-functional calculations using the LMTO and the LAPW methods. Both hexagonal and Bernal stacked structures are considered. The BLG is a zero-gap semiconductor like the isolated layer of graphene. We find that while strain alone does not produce a gap in the BLG, an electric field does so in the Bernal structure but not in the hexagonal structure. The topology of the bands leads to Dirac circles with linear dispersion in the case of the hexagonally stacked BLG due to the interpenetration of the Dirac cones, while for the Bernal stacking, the dispersion is quadratic. The size of the Dirac circle increases with the applied electric field, leading to an interesting way of controlling the Fermi surface. The external electric field is screened due to polarization charges between the layers, leading to a reduced size of the band gap and the Dirac circle. The screening is substantial in both cases and diverges for the Bernal structure for small fields as has been noted by earlier authors. As a biproduct of this work, we present the tight-binding parameters for the free-standing single layer graphene as obtained by fitting to the density-functional bands, both with and without the slope constraint for the Dirac cone.Comment: 7 pages, 7 figure

Modeling and simulation of graphene field effect transistor (GFET)

Graphene based top-gated Field effect transistor (GFET) is designed and simulated using the device simulator packages. The paper describes fabrication process and the device simulation aspects of the GFET device. Two devices with different gate lengths of 200nm and 350nm are simulated. Device simulations are carried out in open source TCAD software package. The results indicate a depletion FET type operation in which ON/OFF current ratio of 2.25 is obtained

Electronic and Magnetic Structure of the (LaMnO3_3)2n_{2n}/(SrMnO3_3)n_n Superlattices

We study the magnetic structure of the (LaMnO$_3$)$_{2n}$/(SrMnO$_3$)$_n$ superlattices from density-functional calculations. In agreement with the experiments, we find that the magnetism changes with the layer thickness `n'. The reason for the different magnetic structures is shown to be the varying potential barrier across the interface, which controls the leakage of the Mn-e$_g$ electrons from the LMO side to the SMO side. This in turn affects the interfacial magnetism via the carrier-mediated Zener double exchange. For n=1 superlattice, the Mn-e$_g$ electrons are more or less spread over the entire lattice, so that the magnetic behavior is similar to the equivalent alloy compound La$_{2/3}$Sr$_{1/3}$MnO$_3$. For larger n, the e$_g$ electron transfer occurs mostly between the two layers adjacent to the interface, thus leaving the magnetism unchanged and bulk-like away from the interface region.Comment: 5 pages, 5 figure

Duplex process for production of low carbon ferrochrome

The Duplex Process for the production of low carbon ferro chrome has been highlighted and its advantage over Perrin process has been brought cut. The production of Low Carbon Ferro-chrome in Perrin process demands rigid operating conditions compared to the Duplex process. The life of the refractories in the Duplex process are also longer compared to Perrin process and the specific raw material consumption and energy are comparable. The demand for Low catbon Ferrochrome is reducing due to adoption of V. 0. D. and A. 0. D. process in India by the major stainless steel manufacturers. However, the import-ance of Low Carbon Ferrochrome will continue for a few years till the new process of stainless steel manufacture are adopted by all