MOSSBAUER SPECTROMETRY OF FE(CU)MB-TYPE NANOCRYSTALLINE ALLOYS .1. THE FITTING MODEL FOR THE MOSSBAUER-SPECTRA

A fitting model based on the use of two independent blocks resulting f rom distributions of a hyperfine held and of one sextet of lorentzian lines is discussed for Mossbauer spectra recorded for Fe(Cu)MB nanocry stalline alloys. One distributed subspectrum is ascribed to the amorph ous residual matrix, while the other independent block, from the hyper fine-field distribution, is attributed to Fe atoms located in the so-c alled interface zone. This region comprises atoms of nanocrystalline-g rain surfaces and also atoms originating from the amorphous precursor, in close contact with the nanocrystalline grains. A sextet of lorentz ian lines is attributed to the crystalline grains that have emerged fr om the amorphous alloy, which are unambiguously identified as alpha-Fe phase. The distribution with low hyperfine fields can be eventually a nalysed in terms of two components accounting for the coexistence of e lectric and magnetic hyperfine interactions. In such an analysis, dist ributions of both quadrupolar splittings and hyperfine magnetic fields are employed. Examples of the present fitting model are provided for Mossbauer spectra of FeCuMB (M = Zr, Ti, and NbCr) nanocrystalline all oys in the first stage of crystallization. The spectra have been recor ded under various experimental conditions comprising low (77 K) and hi gh (373 K) temperatures as well as an external magnetic field. More de tailed discussion about the consequences of this novel fitting procedu re with respect to the topography of hyperfine interactions within Fe- based nanocrystalline alloys is reported in part II, the following pap er.