Semiconductors with magnetic response at room temperature are sought for spintronics in solid-state devices. Among possible materials for this applications, the magnetic response of FeSi and doped FeSi have produced contradictory results at the nanoscale and more precise measurements and deeper studies are needed to clarify its potential capabilities. For that reason, in this work, single nanowire measurements of ferromagnetic semiconducting FeSi and Mn-doped FeSi nanostructures have been performed using magnetic force microscopy and electron holography. Results obtained confirm the presence of magnetic domains at room temperature with a magnetic moment per Fe atom of Spin polarized density functional calculations confirm a net magnetic moment between in Fe surface atoms with an estimated Curie temperature of 417 K by means of the molecular field approximation. The nanowires present a crystalline B20 cubic structure as confirmed by x-ray diffraction and high-resolution electron microscopy. Their electrical transport measurements confirm p-type nature and thermal activation. A remanent magnetization of 1.5 × 10−5 emu and 0.5 × 10−5 emu was measured at room temperature for FeSi and Mn-doped FeSi respectively, with spin freezing behavior around 30 K for the Mn-doped nanowires.

We report the synthesis of high Curie temperature (TC > 800 K) Mn-doped CoSi nanowires. CoSi and Co1–xMnxSi 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.