Synthesis and crystal growth ofCs0.8(FeSe0.98)2: a new iron-basedsuperconductor with Tc = 27 K

Abstract

We report on the synthesis of large single crystals of a new FeSe layer superconductorCs0.8(FeSe0.98)2. X-ray powder diffraction, neutron powder diffraction and magnetization measurementshave been used to compare the crystal structure and the magnetic properties ofCs0.8(FeSe0.98)2 with those of the recently discovered potassium intercalated systemKxFe2Se2. The newcompound, Cs0.8(FeSe0.98)2, shows a slightly lower superconducting transition temperature (Tc = 27.4 K) in comparisonto 29.5 in (K0.8(FeSe0.98)2). The volume of the crystal unit cell increases by replacing K by Cs—thec parametergrows from 14.1353(13) to 15.2846(11) Å. For the alkali metal intercalated layered compounds known so far,(K0.8Fe2Se2 andCs0.8(FeSe0.98)2), theTc dependence on the anion height (distance between Fe layers and Se layers) wasfound to be analogous to those reported for As-containing Fe superconductors andFe(Se1 − xChx), whereCh = Te, S.