Single-Crystal Growth and Small Anisotropy of the Lower Critical Field in Oxypnictides: NdFeAsO1 − xFx

Abstract

High-quality single crystals of the unconventional superconductor NdFeAsO1 − xFx were grown. We developed a new optimized flux technique to overcome the difficulties in single-crystal growth and the sample quality limitations of NdFeAsO1 − xFx. The normal state of the F-doped samples exhibits simple metallic behavior upon cooling down from room temperature, followed by a sharp superconducting transition. The values of residual resistivity ratio (RRR) is 3.2, 6.4, and 10.3 for x = 0.1, 0.15, and 0.2, respectively. Both the large RRR and the narrow superconducting transition signpost the high quality of the crystals. We have examined the in- and out-of-plane lower critical fields, and the field at which vortices penetrate the sample of NdFeAsO1 − xFx (x = 0.1). The anisotropy ratio [γHc1 (0)] increased slightly with increasing temperature from 0.8 Tc to Tc. The temperature dependence of the first vortex penetration field was obtained under the static magnetic field, H, parallel to the c- and ab- axis, and pronounced changes in the Hc1(T) curvature were observed, which are attributed to the multi-band superconductivity.

Bulk and Single Crystal Growth Progress of Iron-Based Superconductors (FBS): 1111 and 1144

“…Hence, we need more research in this direction through advanced techniques. Single crystals: Many groups have reported the single crystal growth of this family [50,111,[112][113][114][115][116][117][118] using different growth parameters. However, it is not an easy task to obtain high-quality and suitable-sized 1111 crystals.…”

“…Due to these issues, there are many unresolved features concerning their superconducting properties. Mostly, the following two methods are used to grow the single crystals of the 1111 family: Single crystals: Many groups have reported the single crystal growth of this family [50,[111][112][113][114][115][116][117][118] using different growth parameters. However, it is not an easy task to obtain high-quality and suitable-sized 1111 crystals.…”

Influence of Artificially Macroscopical Drilling on the Crystal Growth Orientation of Single Domain SmBCO Bulk Superconductor

“…Due to their zero-resistance property and diamagnetism, superconducting materials have attracted significant attention since their discovery [1][2][3]. Single domain (RE)Ba 2 Cu 3 O 7−δ (REBCO) (RE a is rare-earth element, such as Nd, Sm, Gd, and Y) bulk superconductors have been widely investigated during the past three decades because of their remarkable potential in various applications areas [4][5][6][7][8].…”