Short-range magnetic order and effective suppression of superconductivity by manganese doping in LaFe_(1-x)Mn_xAsO_(1-y)F_y

摘要

We present a study of the structural and physical properties of directly hole-doped LaFe_(1-x)Mn_xAsO (x = 0.0 - 0.2) and the influence of charge compensation by additional F doping in LaFe_(0.9)Mn_(0.1)AsO_(1-y)F_y (y = 0.1 - 0.5). High-quality polycrystalline samples were prepared for Mn-doped LaFei_xMn^AsO and the low doping regime in LaFe_(0.9)Mn_(0.1)AsO_(1-y)F_y (y =0.1 and 0.2) using a solid-state metathesis reaction. The unit cell increases upon Mn doping, but decreases again when additional F is inserted. The semiconducting character of LaFe_(1-x)Mn_xAsO decreases with additional F doping. Muon spin relaxation (μSR) measurements reveal short-range magnetic order in LaFe_(1-x)Mn_xAsO and a suppression of magnetism by additional electron doping with fluoride in LaFe_(0.9)Mn_(0.1)AsO_(1-y)F_y. Superconductivity remains absent even though the electronic preconditions are fulfilled in electron-doped LaFe_(0.9)Mn_(0.1)AsO_(1-y)F_y at x > 0.1, which is suggestive of effective pair breaking by Mn in this system.