Iron‐Based Superconductors with Extended FeX₄ (X = As and Se) Tetrahedra

Abstract

Keywords: Iron / Pnictides / Chalcogens / Superconductors / Intermetallic compounds Intermetallic compounds have been investigated over several decades for their interesting structural and physical properties, including magnetism and superconductivity. Among these, metal pnictides and chalcogenides of transition metals show diversity of bonding ranging from appreciable covalency to metal-metal bonds, which makes these compounds highly complex. ZrCuSiAs and ThCr 2 Si 2 are of interest, because they provide an opportunity to design interesting intermetallics with tetrahedral layers exhibiting quasitwo-dimensional behavior. However, these metal pnictides and chalcogenides were not well known for their supercon-

Syntheses of a series of BaCu2−xAgxSe2 (x = 0 – 1.0) selenides and evaluation of their thermoelectric properties

“…The arrangement of M1/M2 and Se atoms in the chains is similar to the coordination environments of transition metals and Se atoms in the tetragonal FeSe, 50 tetragonal BaCu 2 Se 2 , 30 and BaAgSe 2 10 structures. The M2⋯M2 interactions (2.7768(10) Å to 2.8162(7) Å) in the BaCu 2− x Ag x Se 2 structure are weak and considerably longer than the Cu–Cu distances (2.556(1) Å) of Cu metal 51 but shorter than the Ag–Ag distances (2.889(1) Å) of the Ag metal.…”

The effect of antimony doping on the transport and magnetic properties of Ce(O/F)FeAs

“…We emphasize that this is the first example among electron-doped oxypnictide superconductors where the T c increases as a result of a decrease in chemical pressure (an increase in lattice parameters). Increase in chemical pressure through substitution of smaller rare earths in LnOFeAs-based superconductors results in an enhancement of the superconducting transition temperature (T c ) [14]. Application of pressure on F-doped LaO 0.9 F 0.1 FeAs also leads to enhancement in T c from 26 K (ambient pressure) to 43 K (4 GPa) [15].…”

BaCuTP2 (T = Al, Ga, In): a semiconducting black sheep in the ThCr2Si2 intermetallic family

“…The [M 2 X 2 ]-layers are stacked along the crystallographic [001] direction with the A-site cations located in the interlayer spaces. The unique structural features of these materials give rise to a variety of properties such as superconductivity, [3][4][5][6] magnetism, [7][8][9] and, recently, thermoelectricity. [10][11][12] Selective preferences for elements to occupy either the M-site or the X-site have been noticed.…”