Magnetic ordering and electron correlation of iron-based superconductor (Ca3Al2O5−x)(Fe2As2) from first-principles study

• Published in: Solid state communications 2013-10, Vol.172, p.41-48
• Main Authors: Zhang, Yun-Li, Tao, Xiang-Ming, Tan, Ming-Qiu
• Format: Article
• Language: English
• Subjects: A. Iron-based superconductor; B. magnetic ordering; C. Electronic structure; Condensed matter: electronic structure, electrical, magnetic, and optical properties; Exact sciences and technology; Physics; Properties of type I and type II superconductors; Superconductivity
• ISSN: 0038-1098; 1879-2766
• DOI: 10.1016/j.ssc.2013.08.014

In this paper the density-functional theory calculations are performed on the newly discovered superconductor (Ca3Al2O5−x)(Fe2As2). Within the LSDA approach, the total-energy calculations show that the ground state is in striped anti-ferromagnetic (S-AFM) order for (Ca3Al2O5−x)(Fe2As2) (x=0 and 0.5) and oxygen vacancy is easily formed at 8g site for (Ca3Al2O5−x)(Fe2As2) (x=0.5). The electronic densities of the states around the Fermi energy (EF) mainly come from the Fe-3d states for both nonmagnetic and S-AFM configurations of (Ca3Al2O5−x)(Fe2As2) (x=0) and the total DOSs (both spins) around the EF become obviously larger when oxygen vacancies are introduced at 8g site. Considering electron correlation, it is found that a strong correlation insulating gap develops with the increase of Hubbard U for the parent compound (Ca3Al2O5)(Fe2As2), and the transition from insulator to metal is forecasted when oxygen vacancies are introduced in (Ca3Al2O5−x)(Fe2As2) system. The ground state of this compound could be ascribed as a correlated insulator and the oxygen vacancy yields its transition from insulator to metal. •The stable configurations of (Ca3Al2O5−x)(Fe2As2) (x=0, 0.5) have been determined by the first-principles method.•The local densities of states near EF for both NM and S-AFM configurations have been studied numerically.•The influence of oxygen vacancies on the magnetic and electrical properties of the stable phase has been investigated.•The band structures and Fermi surfaces for both NM and S-AFM phases of (Ca3Al2O5)(Fe2As2) have been calculated and discussed.•A transition from insulator to metal has been predicted for S-AFM (x=0, 0.5) phases.