The production and structural characterization of gas-evaporated nanoparticles in the Fe1-x Crx system, with 0<x<0.83 are reported. The results show that for x∼0.5 the metastable σ-FeCr can be stabilized and it constitutes up 60 wt % of the material. The sample with the highest σ-FeCr content is further analyzed to study the structural and the magnetic properties of this phase and its thermal stability. The σ-FeCr phase is weakly magnetic with an average magnetic moment of 0.1 μB per Fe atom and a Curie temperature below ∼60 K. It is stable up to 550 K where it starts to transform to bcc-FeCr. Annealing at 700 K yields Cr2 O3 due to Cr surface segregation and affects the magnetic behavior of the system, which is dominated by interparticle interactions. © 2005 American Institute of Physics.