Superconductivity in LnFePO (Ln = La, Pr, and Nd) single crystals
Abstract
Single crystals of the compounds LaFePO, PrFePO, and NdFePO have been prepared by means of a flux growth technique and studied by electrical resistivity, magnetic susceptibility and specific heat measurements. We have found that PrFePO and NdFePO display superconductivity with values of the superconducting critical temperature Tc of 3.2 K and 3.1 K, respectively. The effect of annealing on the properties of LaFePO, PrFePO, and NdFePO is also reported. The LnFePO (Ln = lanthanide) compounds are isostructural with the LnFeAsO1-xFx compounds that become superconducting with Tc values as high as 55 K for Ln = Sm. A systematic comparison of the occurrence of superconductivity in the series LnFePO and LnFeAsO1-xFx points to a possible difference in the origin of the superconductivity in these two series of compounds.