Superconductivity at 23 K in Pt doped BaFe₂As₂single crystals

Abstract

We report superconductivity in single crystals of the new iron-pnictide system BaFe(1.90)Pt(0.10)As(2) grown by a self-flux solution method and characterized via x-ray, transport, magnetic and thermodynamic measurements. The magnetic ordering associated with a structural transition at 139 K present in BaFe(2)As(2) is completely suppressed by substitution of 5% Fe with Pt and superconductivity is induced at a critical temperature T(c) = 23 K. Full diamagnetic screening in the magnetic susceptibility and a jump in the specific heat at T(c) confirm the bulk nature of the superconducting phase. All properties of the superconducting state-including the transition temperature T(c), the lower critical field H(c1) = 200 mT, the upper critical field H(c2)≈ 65 T, and the slope ∂H(c2)/∂T-are comparable in value to those found in other transition metal-substituted BaFe(2)As(2) series, indicating the robust nature of superconductivity induced by substitution of Group VIII elements.

Superconductivity induced by doping platinum inBaFe2As2

“…23 Their results are consistent with ours although they report the result for only one doping level. …”

“…In the sample with x = 0.1, we get a maximum transition temperature T c of about 25 K, which is determined by a standard method, i.e., using the crossing point of the normal state background and the extrapolation of the transition part with the most steep slope (as shown by the dashed lines in Fig.5). The transition width determined here with the criterion of 10-90%ρ n (ρ n means the normal state resistivity at the onset transition point) is about 1.87 K. According to Saha et al 23 , the superconducting transition temperature T c on the single crystal with x = 0.1 is about 23 K, while the transition width is about 1.5 K. Comparing with our data on the polycrystalline sample with x = 0.1, the superconducting transition temperature T c of our sample is a little higher than theirs, which may be caused by the slight difference of the doping level. Meanwhile, the superconducting resistive transition width in our samples is a little bigger than theirs, which may be caused by the grain boundaries of polycrystalline samples.…”

“…Actually, even in the single crystal samples with the doping to the Fe-sites, RRR is also quite small. For example, in the single crystals of BaFe 2−x M x As 2 (M = Pt, Pd, Rh) 19,23 , RRR is just around 2. For the single crystals with Ni and Co doping, 22,24 the RRR can at most rises up to 3, which is much below the value of the (Sr,Ba) 1−x K x Fe 2 As 2 which can go up to about 8-10 in very clean samples.…”

Superconductivity and magnetism in platinum-substitutedSrFe2As2single crystals

“…4. An isentropic construction, as done previously 26,31 , gives a value of ∆C p /T c ≃ 17 mJ/mol K. Assuming the BCS weak-coupling approximation ∆C p /γT c =1.43 the value of γ is estimated to be ∼ 12 mJ/mol K 2 , comparable to that found in other transition metal-doped BaFe 2 As 2 superconductors 26 . In Ref.…”

“…Recently superconductivity has been discovered with a transition temperature T c of 23 K in single-crystal samples of BaFe 2 As 2 with 5% Fe substituted by Pt (Ref. 26), and later shown to exist in a range of Pt substitutions in polycrystalline samples of the BaFe 2−x Pt x As 2 series 28 . The transition temperatures in BaFe 2−x Pt x As 2 are comparable to those of other transition metal substituted BaFe 2 As 2 systems, but occur over a substitution range that extends slightly beyond that of the related Group VIII substitution systems BaFe 2−x Ni x As 2 and BaFe 2−x Pd x As 2 (Ref.…”