Effect of Cr on the Hyperfine Magnetic Field of Fe in Ferritic Fe-Cr-5Ni Alloys

Hyperfine magnetic fields of 57Fe in ferritic Fe-Cr-5%Ni alloys have been measured in a concentration range from 0 to 60%Cr by Mössbauer spectroscopy at room temperature. The hyperfine magnetic field distributions are computed from the experimental Mössbauer spectra.The mean hyperfine magnetic field 〈H〉 depends linearly on Cr content xCr, as expressed by an empirical relation; 〈H〉⁄T=33.5−0.36 xCr (at%), whose slope being somewhat larger than that for Fe-Cr alloys. The full width at a half maximum of the hyperfine magnetic field distribution becomes constant in a concentration range from 25 to 50%Cr.The experimental hyperfine magnetic field distributions are numerically analyzed by considering the effect of Cr and Ni in the first and the second neighbor atomic shells on the hyperfine magnetic field of 57Fe. The resultant hyperfine magnetic field coefficients of Cr and Ni in the first neighbour atomic shell change from −3.9 to −2.4 T and 0.6 to −1.2 T, respectively, while the Cr content increases from 0 to 50%.