Intertekstual Measurings of Ukrainian and German Poetry of 40th Years of XX Age

Статтю присвячено аналізу української та німецької поезії 40-х років у контексті їх інтертекстуальної природи. У ній розглядається поезія Андрія Малишка та Еріха Вайнерта. Із позицій порівняльного літературознавства проана- лізовано традиційні образи, що постають із міжтекстової культури обох літератур. The article is devoted to the analysis of Ukrainian and German poetry of 40th in context of their intertextual nature. Much attention is paid to the poetry of Andrej Malischko and Erich Weinert. From the position of comparative literature studies is carried out the analysis of traditional images that rise from the intertextual culture of both literatures

Role of Disorder in Mn:GaAs, Cr:GaAs, and Cr:GaN

We present calculations of magnetic exchange interactions and critical temperature T_c in Mn:GaAs, Cr:GaAs and Cr:GaN. The local spin density approximation is combined with a linear-response technique to map the magnetic energy onto a Heisenberg hamiltonion, but no significant further approximations are made. Special quasi-random structures in large unit cells are used to accurately model the disorder. T_c is computed using both a spin-dynamics approach and the cluster variation method developed for the classical Heisenberg model. We show the following: (i) configurational disorder results in large dispersions in the pairwise exchange interactions; (ii) the disorder strongly reduces T_c; (iii) clustering in the magnetic atoms, whose tendency is predicted from total-energy considerations, further reduces T_c. Additionally the exchange interactions J(R) are found to decay exponentially with distance R^3 on average; and the mean-field approximation is found to be a very poor predictor of T_c, particularly when J(R) decays rapidly. Finally the effect of spin-orbit coupling on T_c is considered. With all these factors taken into account, T_c is reasonably predicted by the local spin-density approximation in MnGaAs without the need to invoke compensation by donor impurities.Comment: 10 pages, 3 figure

Electronic structure, chemical bonding, and magnetic properties in the intermetallic series Sc2Fe(Ru1−xRhx)5B2 from first principles

First-principles, density-functional studies of the electronic structure, chemical bonding, ground-state magnetic ordering, and exchange-interaction parameters have been performed for the entire Sc2Fe(Ru1−xRhx)5B2 series of magnetic compounds. The results indicate that their magnetic properties depend in an extremely sensitive way on the degree of band filling and bandwidth. Continuous substitution of Ru by Rh changes the ground state from an antiferromagnet to a ferromagnet, as well as increases the effective spin moment caused by filling the bands with five additional electrons per formula unit together with a narrowing of the 4d band. The correlations between the character of the chemical bonding and the resulting exchange couplings are discussed. The enhancement of Fe-Fe exchange coupling caused by Rh∕Ru atoms is estimated. Trends for the macroscopic ordering temperatures are correctly reproduced

Anisotropic pairing in the iron pnictides

We determine the anisotropy of the spin fluctuation induced pairing gap on the Fermi surface of the FeAs based superconductors as function of the exchange and Hund's coupling $J_{H}$. We find that for sufficiently large $J_{H}$, nearly commensurate magnetic fluctuations yield a fully gapped $s^{\pm}$-pairing state with small anisotropy of the gap amplitude on each Fermi surface sheet, but significant variations of the gap amplitude for different sheets of the Fermi surface. In particular, we obtain the large variation of the gap amplitude on different Fermi surface sheets, as seen in ARPES experiments. For smaller values of Hund's coupling incommensurate magnetic fluctuations yield an $s^{\pm}$-pairing state with line nodes. Such a state is also possible once the anisotropy of the material is reduced and three dimensional effects come into play.Comment: Revised and substantially extended version, accepted for publication in Phys. Rev. B; 9 pages, 6 figure