Spin- and charge density around Rh impurity in α-Fe studied by 57Fe Mössbauer spectroscopy

Random solution of rhodium in ferromagnetic α-Fe of the BCC structure has been investigated by means of the 14.4-keV Mössbauer transition in 57Fe at room temperature. Rhodium atoms have been randomly substituted on the iron sites with the concentration up to 15 at.%. Contributions to the hyperfine field and isomer shift on the iron nuclei have been determined as the function of the distance between iron nucleus and rhodium impurity up to the third co-ordination shell. Rhodium atom as the nearest iron neighbor changes iron hyperfine field by +0.73 T, as the second neighbor makes change by +0.70 T and finally as the third neighbor changes the field by +0.43 T. Corresponding changes in the isomer shift are as follows: −0.015 mm/s, −0.005 mm/s and +0.039 mm/s. The average hyperfine field and the isomer shift increase linearly versus rhodium concentration at rates 0.156 T/at.% and 4.42 × 10−3 mm/(s at.%), respectively. Hence, addition of rhodium lowers the electron density ρ on the iron nucleus at the rate ∂ρ/∂c = −1.52 × 10−2 electron a.u.−3 (at.%)−1.