title: Effects of Co and Mn doping in K0.8Fe2-ySe2 revisited.
abstract: Accumulated evidence indicates that phase separation occurs in potassium intercalated iron selenides, a superconducting phase coexisting with the antiferromagnetic phase K2Fe4Se5, the so-called '245 phase'. Here, we report a comparative study of substitution effects by Co and Mn for Fe sites in K0.8Fe2-ySe2 within the phase separation scenario. Our results demonstrate that Co and Mn dopants have distinct differences in occupancy and hence in the suppression mechanism of superconductivity upon doping of Fe sites. In K0.8Fe2-xCoxSe2, Co prefers to occupy the lattice of the superconducting phase and suppresses superconductivity very quickly, obeying the magnetic pair-breaking mechanism or the collapse of the Fermi surface nesting mechanism. In contrast, in K0.8Fe1.7-xMnxSe2, Mn shows no preferential occupancy in the superconducting phase or the 245 phase. The suppression of superconductivity can be attributed to restraining of the superconducting phase and meanwhile inducing another non-superconducting phase by Mn doping.
authors.affiliation: Research and Development Center for Functional Crystals, Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing 100190, People's Republic of China.
authors.forename: Tingting
authors.initials: T
authors.lastname: Zhou
authors.forename: Xiaolong
authors.initials: X
authors.lastname: Chen
authors.forename: Jiangang
authors.initials: J
authors.lastname: Guo
authors.forename: Shifeng
authors.initials: S
authors.lastname: Jin
authors.forename: Gang
authors.initials: G
authors.lastname: Wang
authors.forename: Xiaofang
authors.initials: X
authors.lastname: Lai
authors.forename: Tianping
authors.initials: T
authors.lastname: Ying
authors.forename: Han
authors.initials: H
authors.lastname: Zhang
authors.forename: Shijie
authors.initials: S
authors.lastname: Shen
authors.forename: Shunchong
authors.initials: S
authors.lastname: Wang
authors.forename: Kaixing
authors.initials: K
authors.lastname: Zhu
mesh_terms: D003035:Cobalt / Q000737:chemistry*; D004553:Electric Conductivity; D058085:Iron Compounds / Q000737:chemistry*; D008280:Magnetics; D008345:Manganese / Q000737:chemistry*; D008956:Models, Chemical; D011188:Potassium / Q000737:chemistry*; D018036:Selenium Compounds / Q000737:chemistry*
chemical_list: D058085:Iron Compounds; D018036:Selenium Compounds; D003035:Cobalt; D008345:Manganese; D011188:Potassium