| 학회 | 한국재료학회 |
| 학술대회 | 2016년 가을 (11/16 ~ 11/18, 경주 현대호텔) |
| 권호 | 22권 2호 |
| 발표분야 | H. 한-일 재료공학 워크샵 |
| 제목 | Theoretical and experimental approaches for crystallographic stability of LnFeAsO |
| 초록 | The discovery of superconductivity in iron-based mixed anion compound LaFeAsO1-xFx[1] reported by Kamiahra et al. in 2008 has evoked enthusiasm for extensive research on these materials. Soon after this discovery, researchers reported that the Tc of LnFeAsO¬1-xFx (Ln = Nd, Sm and Gd etc.) jumps up to ~58 K[2], which is the highest except for cuprates high-Tc superconductors in ambient pressure. Moreover, an upper critical magnetic flux (0Hc2) of these compounds exceeds 100 T, indicating potential of this material for applications. Undoped LnFeAsO exhibits an antiferromagnetic phase transition, stimulated by structure phase transition. As carriers are doped, the antiferromagnetic phase disappears, and superconducting phase appears. Therefore, electronic and magnetic phase diagram of LnFeAsO-1-xFx (Ln = La, Ce and Sm) has been studied intensively. Although GdFeAsO¬1-xFx exhibits relatively-high Tc, there had not been a report about electrical phase diagram with reliable chemical component. In this report, I will report thermal and electronic properties of GdFeAsO1-xFx using both of experimental procedure and density functional theory. Polycrystalline GdFeAsO¬1-xFx (x = 0-0.107) were prepared via solid state reaction. The anomaly kink of ρ-T curve at Tanom~135 K has been definitely suppressed by F-doping and bulk superconducting phase wad observed for x ＞ 0.066. The highest Tc of 46.6 K (Tc onset = 47.8 K) is attained at x = 0.102 and this value is highest among GdFeAsO1-xFx synthesized under ambient pressure. The electronic and magnetic properties of the mother material GdFeAsO have been studied using first-principles electron structure calculations based on the generalized gradient approximation in the density functional theory. The crystal unit cell structure of GdFeAsO has a tetragonal layered structure with the space group P4/nmm. In the actual calculations for GdFeAsO, we have studied three different magnetic states: 1) nonmagnetic (NM), 2) AFM with Checkerboard (AFM-C, Figure 1), 3) AFM with Stripe (AFM-S, Figure 1). The present calculation by using Vienna Ab -initio Simulation Package (VASP) predicts that the ground state of GdFeAsO is antiferromagnetic with a stripe type magnetic moment alignment. |
| 저자 | T. HIBINO, A. SAKURAI, H. SHIOZAWA, M. MATOBA, Y. KAMIHARA |
| 소속 | Keio Univ. |
| 키워드 | superconductivity; iron based superconductor; ab initio calculation |
