Contamination from Magnetic Starting Materials in Flux-grown Single Crystals of RFeAsO Superconductors
|Title||Contamination from Magnetic Starting Materials in Flux-grown Single Crystals of RFeAsO Superconductors|
|Publication Type||Journal Article|
|Year of Publication||2011|
|Authors||Yan J-Q, Xing Q, Jensen B, Xu H, Dennis KW, McCallum RW, Lograsso TA|
|Journal Title||Physical Review B|
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.