{\gamma}-Fe phase plasma-induced on the surface of thin S3A alloy ribbons

Amorphous alloy ribbons of Fe₇₇Cr₂B₁₆Si₅ were exposed to cold plasmas of N₂ and Ar?CN₂ at temperatures lower than T_x?=?808?K. The conversion X-ray M?ssbauer spectra of the plasma-exposed ribbons consist of a singlet and a broadened magnetic sextet. The singlet with isomer shift $\updelta = -0.11$ ?mm/s can be assigned to $\upgamma $ -Fe austenite phase. Minor bulk magnetic changes in the alloy were measured as a consequence of these treatments; e.g. the relative intensities A23 of the transmission M?ssbauer spectra of the untreated and treated samples, were 3.22 and 3.56, respectively, the B_hf values changed from 22.9?T (untreated sample) to 22.4?T (plasma treated samples). Unexpectedly, the $\upgamma $ -Fe phase can also be produced by simply heating the alloy ribbons under N₂ flux at temperatures as low as 423?K. M?ssbauer data of the crystallized samples are also reported, and a qualitative assessment on the mechanical properties of the Fe₇₇Cr₂B₁₆Si₅ alloy associated with the plasma and/or temperature surface induced $\upgamma $ -Fe phase is given.