K. Racka

Aerosol nanoparticles in the Fe1−xCrx system: Room-temperature stabilization of the σ phase and σ→α-phase transformation

The production and structural characterization of gas-evaporated nanoparticles in the Fe1−xCrx 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 60wt% 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 0.1μB per Fe atom and a Curie temperature below ∼60K. It is stable up to 550K where it starts to transform to bcc-FeCr. Annealing at 700K yields Cr2O3 due to Cr surface segregation and affects the magnetic behavior of the system, which is dominated by interparticle interactions.