Superconducting properties of the oxygen-deficient iron oxyarsenideTbFeAsO1−δfrom underdoped to overdoped compositions

Abstract

A wide-range doping was achieved by a high-pressure method for TbFeAsO 1−␦ from "underdoped" to "overdoped" superconducting compositions throughout the optimized superconductivity ͑T c of 44 K͒. T c vs ␦ shows a dome-shaped feature, while T c vs the lattice constant likely follows a unique empirical curve over the doping range. The relatively large amount of oxygen vacancies up to ϳ0.3 per the formula unit was introduced possibly because of the smaller replacement Tb than the other Ln ͑rare-earth element͒ in the LnFeAsO 1−␦ system.

Magnetic and electrical properties and carrier doping effects on the iron-based host compound Sr2ScFeAsO3

“…In The anisotropic lattice feature is remarkably contrast with what was found for LaFeAsO 1-δ [26] and TbFeAsO 1-δ [27], in which the unit cell is isotropically contracted with increasing amount of the oxygen vacancies. Nevertheless, the systematic lattice change is indicative of successful doping of the oxygen vacancies into the structure, although we were unable to measure the net oxygen concentration by a chemical method because of the toxic effects.…”

“…About 20 mg of the samples were full oxidized at 1500 ºC for 24h in air then were slowly cooled to room temperature. [27], it is suggested that the anomaly is due to formation of the spin density wave (SDW). It is interesting that a comparable anomalous feature of the electrical resistivity, even it is fairly weak, can be seen in the data reported independently by others [24].…”

“…We thus focused on a specific Fe-based compound that has increasing distance between the layers, as was successful in the oxyarsenides such as LaFeAsO 1-δ [26] and TbFeAsO 1-δ [27].…”

Large decrease in the critical temperature of superconductingLaFeAsO0.85compounds doped with 3% atomic weight of nonmagnetic Zn impurities

“…Regarding LaFeAsO 1−␦ , the tetragonal lattice parameters a and c decrease with increasing ␦ as well as what was found for the compounds TbFeAsO 1−␦ . 36 This probably reflects combination of Coulomb attractive forces between the charged ͓LaO 1−␦ ͔ 1+2␦ and ͓FeAs͔ 1−2␦ layers and amount of vacate sites for oxygen atoms. In sharp contrast to the observation, the Zn substitution resulted in an anisotropic change in the lattice parameters: c of LaFe 1−x Zn x AsO 0.85 increases ͑+0.02% at Zn 0.01 ͒ while a decreases much efficiently ͑−0.08%͒ over the substitution.…”

“…The poor quality persisted exceptionally at ␦ =0 ͑not due to a run-to-run error͒ as observed in the high-pressure synthesis of TbFeAsO 1−␦ . 36 It should be emphasized that the optimally carrier-doped samples ͑␦ = 0.15͒ with and without Zn were all prepared under the same high-pressure condition.…”