# High-pressure flux growth, structural, and superconducting properties of LnFeAsO (Ln = Pr, Nd, Sm) single crystals

Zhigadlo, N; Weyeneth, S; Katrych, S; Moll, P; Rogacki, K; Bosma, S; Puzniak, R; Karpinski, J; Batlogg, B (2012). High-pressure flux growth, structural, and superconducting properties of LnFeAsO (Ln = Pr, Nd, Sm) single crystals. Physical Review B (Condensed Matter and Materials Physics), 86(21):214509.

## Abstract

Single crystals of the LnFeAsO (Ln1111, Ln = Pr, Nd, and Sm) family with lateral dimensions up to 1 mm were grown from NaAs and KAs flux at high pressure. The crystals are of good structural quality and become superconducting when O is partially substituted by F (PrFeAsO1−xFx and NdFeAsO1−xFx) or when Fe is substituted by Co (SmFe1−xCoxAsO). From magnetization measurements, we estimate the temperature dependence and anisotropy of the upper critical field and the critical current density of underdoped PrFeAsO0.7F0.3 crystal with Tc ≈ 25 K. Single crystals of SmFe1−xCoxAsO with maximal Tc up to 16.3 K for x ≈ 0.08 were grown. From transport and magnetic measurements, we estimate the critical fields and their anisotropy and find these superconducting properties to be quite comparable to the ones in SmFeAsO1−xFx with a much higher Tc ≈ 50 K. The magnetically measured critical current densities are as high as 109 A/m2 at 2 K up to 7 T, with indication of the usual fishtail effect. The upper critical field estimated from resistivity measurements is anisotropic with slopes of ∼−8.7 T/K (H||ab plane) and ∼−1.7 T/K (H||c axis). This anisotropy (∼5) is similar to that in other Ln1111 crystals with various higher Tc's.

Single crystals of the LnFeAsO (Ln1111, Ln = Pr, Nd, and Sm) family with lateral dimensions up to 1 mm were grown from NaAs and KAs flux at high pressure. The crystals are of good structural quality and become superconducting when O is partially substituted by F (PrFeAsO1−xFx and NdFeAsO1−xFx) or when Fe is substituted by Co (SmFe1−xCoxAsO). From magnetization measurements, we estimate the temperature dependence and anisotropy of the upper critical field and the critical current density of underdoped PrFeAsO0.7F0.3 crystal with Tc ≈ 25 K. Single crystals of SmFe1−xCoxAsO with maximal Tc up to 16.3 K for x ≈ 0.08 were grown. From transport and magnetic measurements, we estimate the critical fields and their anisotropy and find these superconducting properties to be quite comparable to the ones in SmFeAsO1−xFx with a much higher Tc ≈ 50 K. The magnetically measured critical current densities are as high as 109 A/m2 at 2 K up to 7 T, with indication of the usual fishtail effect. The upper critical field estimated from resistivity measurements is anisotropic with slopes of ∼−8.7 T/K (H||ab plane) and ∼−1.7 T/K (H||c axis). This anisotropy (∼5) is similar to that in other Ln1111 crystals with various higher Tc's.

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Item Type: Journal Article, refereed, original work 07 Faculty of Science > Physics Institute 530 Physics English 2012 31 Jan 2013 15:31 05 Apr 2016 16:26 American Physical Society 1098-0121 https://doi.org/10.1103/PhysRevB.86.214509
Permanent URL: https://doi.org/10.5167/uzh-72341