V. V. Bannikov

Novel magnetic half-metallic materials based on ionic insulators doped with nonmagnetic impurities: MgO + B, C, N Systems

It is established that magnesium oxide (a nonmagnetic ionic insulator) exhibits a transition to the state of a magnetic half-metal upon the introduction of nonmagnetic impurities (boron, carbon, or nitrogen) into the crystal lattice. The possibility of obtaining novel magnetic materials for spintronics by doping ionic insulators with nonmagnetic impurities is discussed.

Structural and electronic properties and the fermi surface of the new non-centrosymmetric superconductors: 3.6 K CaIrSi3 and 2.3 K CaPtSi3

Ab initio FLAPW-GGA calculations have been performed to investigate structural properties, electronic band structure, and Fermi surface topology of the newly discovered non-centrosymmetric superconductors: 3.6 K CaIrSi3 and 2.3 K CaPtSi3. As a result, the peculiarities of the crystal structure, electronic bands, total and site-projected l-decomposed densities of states, and the shape of the Fermi surface for CaIrSi3 and CaPtSi3 were obtained and analyzed.

Ab initio search for novel bipolar magnetic semiconductors: Layered YZnAsO doped with Fe and Mn

Very recently, the newest class of spintronic materials, where reversible spin polarization can be controlled by applying gate voltage: so-called bipolar magnetic semiconductors (Xingxing Li et al., arXiv:1208.1355) was proposed. In this work, a novel way to creation of bipolar magnetic semiconductors by doping of non-magnetic semiconducting 1111 phases with magnetic dn < 10 atoms is discussed using ab initio calculations of layered YZnAsO doped with Fe and Mn. In addition, more complex materials with several spectral intervals with opposite 100% spin polarization where multiple gate-controlled spin-polarization can be expected are proposed.

Elastic, electronic and magnetic properties of new oxide perovskite BaVO3: A first-principles study

The structural, elastic, magnetic properties, as well as electronic structure and chemical bonding picture of new oxide 3d1-perovskite BaVO3, recently synthesized, were systematically investigated involving the first-principles FLAPW-GGA calculations. The obtained results are discussed in comparison with available experimental data, as well as with those obtained before for isostructural and isoelectronic SrVO3 perovskite.

Peculiarities of EPR in polycrystalline solid solutions Zn 0.95 Fe 0.05 O with different particles morphology: The role of intrinsic defects in formation of magnetic properties

Single-phase polycrystalline samples of Zn0.95Fe0.05O having the wurtzite structure and different morphology of particles were obtained using precursor technologies. It was found by electron spin resonance that iron enters the ZnO crystal lattice in the Fe3+ charge state. Magnetic studies revealed that the obtained samples show weak ferromagnetic properties at 300 K. A correlation between the number of oxygen vacancies and the degree of ferromagnetic ordering was found.

Gas-phase synthesis of hexagonal and cubic phases of aluminum nitride: A method and its advantages

Experimental results obtained in AlN synthesis by the high-temperature gas-phase method and analysis of reaction products phase composition are briefly described. It is demonstrated for the first time that dispersed aluminum nitride can be synthesized by this method from AlF3 in both hexagonal and cubic modifications.

Novel magnetic materials based on semiconducting 1111 phases: Theory and experiment

A brief review of theoretical and experimental studies devoted to the design of novel magnetic materials based on non-magnetic semiconductor phases with the ZrCuSiAs structure type (such as LaCuSO, LaCuSeO, LaZnAsO, YZnAsO, or SrAgSeF) by doping their sublattices with magnetic and non-magnetic substitutional impurities is presented. Using the results of ab initio calculations of the band structure, we discuss the possibility of obtaining new magnetic semiconductors, magnetic metals and half-metals, and also gapless magnetic semiconductors and bipolar magnetic semiconductors based on the 1111 phases. The available experimental data on the synthesis and properties of materials based on semiconducting 1111 phases doped with atoms of alkali-earth and magnetic 3d metals are discussed.

Trends in structural, electronic properties, Fermi surface topology, and inter-atomic bonding in the series of ternary layered dichalcogenides KNi2S2, KNi2Se2, and KNi2Te2 from first principles calculations

By means of the FLAPW-GGA approach, we have systematically studied the structural and electronic properties of tetragonal dichalcogenides KNi2Ch2 (Ch=S, Se, and Te). Our results show that replacements of chalcogens (S→Se→Te) lead to anisotropic deformations of the crystals structure, which are related to the strong anisotropic character of the inter-atomic bonds, where inside the [Ni2Ch2] blocks, mixed covalent–ionic–metallic bonds occur, whereas between the adjacent [Ni2Ch2] blocks and K atomic sheets, ionic bonds emerge. We found that in the sequence KNi2S2→KNi2Se2→KNi2Te2 (i) the overall band structure (where the near-Fermi valence bands are due mainly to the Ni states) is preserved, but the width of the common valence band and the widths of the separate sub-bands and the gaps decrease; (ii) the total DOSs at the Fermi level also decrease; and (iii) for the Fermi surfaces, the most appreciable changes are demonstrated by the hole-like sheets, when a necklace-like topology is formed for the 2D-like sheets and the volume of the closed pockets decreases. Some trends in structural and electronic parameters for ThCr2Si2-type layered dichalcogenides, KNi2Ch2, KFe2Ch2, KCo2Se2, are discussed.

Electronic and magnetic properties of a new 2D diluted magnetic semiconductor La1 − xBaxZn1 − xMnxAsO from Ab initio calculations

Very recently, on the example of hole- and spin-doped semiconductor LaZnAsO, quite an unexpected area of potential applications of quasi-two-dimensional 1111-like phases was proposed (C. Ding et al., Phys. Rev. B 88, 041102R (2013)) as a promising platform for searching for new diluted magnetic semiconductors (DMSs). In this work, by means of the ab initio calculations, we have examined in detail the electronic and magnetic properties of LaZnAsO alloyed with Ba and Mn. Our results demonstrate that Ba or Mn doping transforms the parent non-magnetic semiconductor LaZnAsO into a non-magnetic metal or a magnetic semiconductor, respectively. On the other hand, the joint effect of these dopants (i.e., co-doping Ba + Mn) leads to transition of La0.89Ba0.11Zn0.89Mn0.11AsO into the state of magnetic metal, which is formed by alternately stacked semiconducting non-magnetic blocks [La0.89Ba0.11O] and metallic-like magnetic blocks [Zn0.89Mn0.11As].

Ab initio prediction of new 3D-like phases ThCuSiAs, ThCuGeAs and their structural, mechanical, and electronic properties

New 1111-like quaternary tetragonal Th-based phases: silicide arsenide ThCuSiAs and germanide arsenide ThCuGeAs are proposed in this article. The stabilities of these materials are verified, and the value of their structural, elastic (elastic constants, bulk, shear, and Young’s moduli, compressibility, Pugh’s indicator, Poisson’s ratio, indexes of elastic anisotropy), electronic (densities of electronic states, electronic heat capacity, molar Pauli paramagnetic susceptibility, and the so-called metallicity indexes), and some other properties (Vickers hardness and melting temperatures) are predicted from the first principles calculations. The proposed phases are the first Th-based oxygen-free 1111-like materials, and their syntheses seem very attractive to expand the rather rare group of non-conventional quasi-three-dimensional 1111-like materials.