Evolution of structure, magnetic and transport properties of Fe1-xMnxSe

Abstract

The present paper seeks to investigate effect ofMndoping in superconducting FeSe. It is found that over the entire doping range in Fe1-xMnxSe (0 ≤ x ≤1),Mn does not substitute Fe in the superconducting tetragonal phase. Instead two impurity phases, NiAs type hexagonal phase and NaCl type cubic phase, grow with increasingMncontent. Initially, hexagonal phase has a higher content than the cubic phase but beyond x=0.5, the cubic phase grows rapidly and for x ≥ 0.8, the sample is monophasic with cubic NaCl type structure. The superconducting tetragonal phase content steadily decreases with increasingMnconcentration and completely disappears beyond x=0.5. The premise thatMnnever replaces Fe in the superconducting phase is further strengthened by observation of a sharp drop inAC susceptibility akin to superconducting transition at the Tc of FeSe up to x=0.5. EXAFS studies at the FeKedge also show that the Fe has a four coordinated tetragonal local structure in all compositions below x=0.5, similar to that in FeSe and it gradually changes to a six coordinated one as is expected for aNaCl type cubic phase for x ≥ 0.5. ©2016 IOP Publishing Ltd.