Contamination from Magnetic Starting Materials in Flux-grown Single Crystals of RFeAsO Superconductors

TitleContamination from Magnetic Starting Materials in Flux-grown Single Crystals of RFeAsO Superconductors
Publication TypeJournal Article
Year of Publication2011
AuthorsYan J-Q, Xing Q, Jensen B, Xu H, Dennis KW, McCallum RW, Lograsso TA
Journal TitlePhysical Review B
Volume84
Pages012501
Date Published07/06
Abstract

While the flux growth often provides the best method for obtaining single crystals of new-novel materials, the process is prone to producing crystals with trapped second-phase inclusions. In the case of NdFeAsO single crystals grown out of NaAs flux under ambient pressure, some crystals show a lambda anomaly in the specific heat curve at ~12 K. This anomaly is missing in other crystals from the same batch. We show that the lambda anomaly at 12 K is from residual NdAs starting material which is mainly on the edges of the crystals. The isothermal magnetization of LaFeAsO at 300 K clearly illustrates the effect of ferromagnetic impurities on the magnetic properties of LaFeAsO crystals.

DOI10.1103/PhysRevB.84.012501