High Curie temperature CoSi nanowires by Mn-doping

We report the synthesis of high Curie temperature (T_C > 800 K) Mn-doped CoSi nanowires. CoSi and Co_1-xMn_xSi nanowires were synthesized by chemical vapor deposition. Transmission electron microscopy was used to identify a crystalline B20 cubical structure. Zero-field cooling and field cooling measurements confirm spin disorder behaviour at low temperatures. The magnetic properties of doped samples were explained by means of the Ruderman-Kittel-Kasuya-Yosida interaction where the localized Mn atoms interact with the conduction electrons in CoSi providing a net ferromagnetic moment and explaining spin disorder at low temperatures. An individual CoSi nanowire was experimentally analyzed by performing off-axis electron holography, providing information about its local magnetization. Density functional theory calculations were performed to understand the effects of Mn doping, Si-vacancies, and surface atoms in the magnetic properties at the surface of the nanowire. An estimation of the Curie temperature was made using the mean field approximation.