Tahir Mohiuddin Bhat

Robust thermoelectric performance and high spin polarisation in CoMnTiAl and FeMnTiAl compounds

New quaternary Heusler materials, CoMnTiAl and FeMnTiAl, have been investigated. These alloys are found to be stable in a ferromagnetic phase in Y1 type structure; the stability is also confirmed by various conditions of elastic constants. Both alloys show half-metallic (HM) ferromagnetic character with integer magnetic moments and they present a metallic nature. The values of the minority band gap in CoMnTiAl and FeMnTiAl are found to be 0.50 eV and 0.25 eV respectively. These alloys also possess excellent thermoelectric behaviour with Seebeck coefficients for CoMnTiAl (FeMnTiAl) as 31 μV K−1 (20 μV K−1) at room temperature. Here we report that CoMnTiAl achieves a figure of merit of 0.62 in a wide temperature range while FeMnTiAl achieves 0.77. Thus these new quaternary Heusler alloys can prove to be ultimate candidates for spin valves and for the best thermoelectric applicability over an ample temperature range.

Electronic and Transport Properties of LaNi 4 Sb 12 Skutterudite: Modified Becke–Johnson Approach

We carried out an ab␣initio study of structural, electronic, thermodynamic, and thermoelectric properties of the lanthanum-filled skutterudite, LaNi4Sb12. Generalized gradient approximation and modified Becke–Johnson potentials were employed for the exchange–correlation potential. The electronic structure calculations display the metallic behavior of the compound. The alloy offers low lattice thermal conductivity along with a high Seebeck coefficient with a value of − 158 (μVK−1) at room temperature. The effect of high pressure and temperature on thermal properties like thermal expansion coefficient, heat capacity, and Grüneisen parameter are also investigated by means of a quasi-harmonic Debye model. The large Seebeck coefficient and high power factor exhibited by LaNi4Sb12 make it an attractive candidate for thermoelectric materials.

Evaluation of mechanical and transport properties of Zr2CoSi Heusler alloy

Systematic investigation of mechanical and transport properties of Zr2CoSi within the density functional theory have been analysed. From the elastic constants, the shear modulus, Young’s modulus, Poisson’s ratio, we conclude the ductile nature of alloy. Thermoelectric properties show that Zr2CoSi as an n-type thermoelectric material with a higher increase in Seebeck coefficient with temperature. Further the power factor analysis confirms the heavily doping of the alloy fruitful for increase in thermoelectric performance and its use for the future thermoelectric spin generators.

Structural and electronic properties of half-metallic rare-earth perovskites

Systemic investigation of structural parameters and electronic properties inclusive of band profiles for BaPaO3 and BaUO3 have been performed. The empirical as well as DFT calculated lattice constants are in agreement with the previously reported results. The critical energy values confirm that the BaPaO3 has lesser migration energy than BaUO3. Both, these materials show a semiconducting, direct band gap in the low spin state with 2.3 eV for BaUO3 and for BaPaO3, its value is 3.9 eV.

Transport properties of spin polarised quaternary CoMnVAs alloy

The electronic structure and transport properties of CoMnVAs quaternary Heusler compound has been investigated first time by using the density functional theory. The material was found half-metallic ferromagnet in F-43m structure. Positive values of the different elastic parameters also confirm its structural stability. Present study predicts an energy band gap of 0.55 eV in localized minority spin channel at an equilibrium lattice constant of 5.75A. Post-DFT treatment predicts this material to be an n-type thermoelectric along with a high Seebeck coefficient of -45μV K-1 at room temperature.

Ferromagnetism in half-metallic quaternary FeVTiAl Heusler compound

The electronic structure and magnetic properties of FeVTiAl quaternary Heusler alloy have been investigated within the density functional theory framework. The material was found completely spin-polarized half-metallic Ferromagnet in the ground state with F-43m structure. The structural stability was further confirmed by calculating different elastic constants in the cubic phase. Present study predicts an energy band gap of 0.72 eV calculated in localized minority spin channel at an equilibrium lattice parameter of 6.0A. The calculated total spin magnetic moment of 2 µB/f.u. is in agreement with the Slater-Pauling rule for full Heusler alloys.