Magnetic-hyperfine-field distributions in amorphous Fe90Zr10 Invar alloy and the effect of replacing Fe with Ni and/or Co

Hyperfine-field distributions P(H) were evaluated from Mössbauer spectra of amorphous (a-) Fe90Zr10, (Fe0.8Co0.2)90Zr10, and (Fe0.8Co0.1Ni0.1)90Zr10 alloys recorded at 85 and 300 K with the use of a model-independent field-distribution analysis. Our data analysis unambiguously shows that P(H) for a-Fe90Zr10 at 85 K consists of two broad Gaussian distributions centered around ~96 and ~200 kG with standard deviations of 36 and 46 kG, respectively. Partial replacement of Fe with (Co,Ni) results in a complete suppression of the low-field peak, and P(H) at 85 K now exhibits only one Gaussian peak at 312 and 296 kG, respectively, for Co- and (Co,Ni)-substituted alloys. Together with other relevant results on a-Fe100-xZrx alloys existing in the literature, our data find a straightforward explanation in terms of a model recently proposed by one of us