Influence of the Fe concentration on the superconducting properties of Fe 1−y Se.

M. L. AMIGÓ; M. V. ALE CRIVILLERO; D. G. FRANCO; J. GUIMPEL; G. NIEVA

Bariloche, Río Negro

Conferencia; Advanced Topics in Magnetism and Superconductivity 2014; 2014

DIV.BAJAS TEMPERATURAS (CAB) ; GERENCIA DE FISICA (CAB) ; GERENCIA D/AREA INVEST Y APLICACIONES NO NUCLEARES ; COMISION NACIONAL DE ENERGIA ATOMICA

We present a comparative study between crystals of Fe deficient Fe 1−y Se and single crystals of the pure β−FeSe phase. The amount of Fe determine which spurious phases are present (metallic Fe, Fe 7 Se 8 , etc). We discuss the influence of the intergrown of the magnetic hexagonal phase (Fe 7 Se 8 ) in the Fe deficient samples and compare this results with the β−FeSe without spurious phases. We characterize the crystal structure through X-ray diffraction. This allow as to know the spurious phases present in the crystals and the possible defects thathave important influence in the transport properties.In the superconducting state, we measure the ab-plane resistivity with field up to 16T . We observe that for all Fe concentration the transition?s width slightly increases with field. This indicate the possibility of a narrow region of liquid vortex. We also measure the resistivity as a function of the angle between the ab-plane and the applied field. These angular dependence at fixed temperatures bellow T c (H=0) are very diferent in both sets of crystals. The iron deficient samples display a vortex pinning related feature at ∼ 56 o off the plane while the pureβ−FeSe phase samples show the persistence of a strong angular dependent magnetoresistance characteristic of the normal state electronic structure.