A. K. Solanki

Optical properties of A1N

Abstract We have performed calculations of the anisotropic frequency dependent dielectric function of AlN, using the linear muffin-tin orbital method within the atomic sphere approximation (LMTO-ASA). Our calculations show that the anisotropy is very small. The effect of introducing empty spheres is to decrease the energy gap by about 20% and to make the dielectric function slightly anisotropic at higher energies. Comparisons with experiments must await experimental results.

Domain-wall magnetoresistance of Co nanowires

Using density functional theory implemented within a tight-binding linear muffin-tin orbital method we perform calculations of electronic, magnetic, and transport properties of ferromagnetic free-standing fcc Co wires with diameters up to 1.5 nm. We show that finite-size effects play an important role in these nanowires resulting in oscillatory behavior of electronic charge and the magnetization as a function of the wire thickness, and a nonmonotonic behavior of spin-dependent quantized conductance. We calculate the magnetoresistance (MR) of a domain wall (DW) modeled by a spin-spiral region of finite width sandwiched between two semi-infinite Co wire leads. We find that the DW MR decreases very rapidly, on the scale of a few interatomic layers, with the increasing DW width. The largest MR value of about 250% is predicted for an abrupt DW in the monatomic wire. We show that, for some energy values, the density of states and the conductance may be nonzero only in one spin channel, making the MR for the abrupt DW infinitely large. We also demonstrate that for the abrupt DW a large MR may occur due to the hybridization between two spin subbands across the DW interface. We do not find, however, such a behavior at the Fermi energy for the Co wires considered.

Ab-initio study of free standing TiO2 clusters: Stability and magnetism

We report the structural behavior of nanoscale Titanium Dioxide (TiO2) clusters as well as their magnetic properties by varying the cluster size with the help of ground state geometries. The clusters of atomic scale rutile (TiO2)n, where n = 1-11, have been considered and geometrically stabilized through the Density Functional Theory as implemented in Vienna ab-initio Simulation Package. It is being observed that as the size of cluster increases from n = 2 to 11, the total energy decreases. The results of formation energy reveal the fact that as the cluster grows, it moves towards the stability and it is observed that n = 11 is the most stable structure. The stabilized clusters are different in geometries and co-ordination numbers. Finally, all the clusters have been investigated with self consistent treatment of spin orbit coupling for magnetism studies. The magnetic properties of free clusters depict oscillatory behavior for magnetic moment with respect to the cluster size.

Magnetism of L10 compounds with the composition MT (M=Rh, Pd, Pt, Ir and T=Mn, Fe, Co, Ni)

The electronic band structure of ordered equiatomic compounds of 3d transition elements (Mn, Fe, Co, Ni) with nonmagnetic 4d and 5d elements (Rh, Pd, Pt, Ir) are investigated by linear muffin-tin orbital calculations. The systematic study considers 3d and 4d/5d spin moments and interatomic exchange interactions, with emphasis on the comparison between ferromagnetic and antiferromagnetic order. Total and site-resolved exchange interactions are calculated from first principles, and the obtained exchange constants are used to estimate ordering temperatures on a mean-field level.

Band structure calculations of heavy fermion YbSbPd and YbSbNi

Dhar et al. [J. Phys. F 18, L41 (1988); and Proceedings of the International Conference on Strongly Correlated Electron Systems Sendai, Japan, 1992 (Plenum, New York, 1987)] have recently measured the low‐temperature specific heat of YbSbPd and YbSbNi. Their measurements yield large values for the specific heat coefficient (1384 states/Ry cell for YbSbPd and 865 states/Ry cell for YbSbNi), and suggest a magnetic transition at low temperature. With a view to understand the ground state of these compounds, we have performed self‐consistent scalar relativistic linear muffin‐tin orbital band structure calculations. Our paramagnetic calculations for YbSbPd and YbSbNi give the density of the states at Fermi level to be 82.94 and 27.96 states/Ry cell, respectively. These give enhancement factors of 16.7 and 30.1 for YbSbPd and YbSbNi. We present results of our calculations of the band structure as well as the Stoner I parameter for these compounds.

Band structure and optical properties of graphite

Abstract We report the first ever calculation of the frequency dependent anisotropic dielectric function of graphite. We have used the LMTO-ASA method including the combined correction terms. On comparison with the experimental data, we find good agreement as far as the anisotropy is concerned. The individual ϵ ⊥ ( ω ) and epsi ; | ( ω ) are also in reasonable agreement with the data.