Mössbauer studies of Ba(Fe(1-x)Ni(x))2As2.

We present detailed (57)Fe Mössbauer effect spectroscopy (MS) measurements at various temperatures for Ba(Fe(1-x)Ni(x))(2)As(2). The isomer shift values for all samples are in the range of 0.42 ± 0.02 mm s(-1), indicating a typical metallic state of divalent Fe ions. The MS spectra of the magnetic samples (up to x = 0.024) are well reproduced by spin density waves subspectra. Both the magnetic ordering temperatures T(M) and the average magnetic hyperfine fields H(eff), decrease with x. The H(eff) values scale linearly with T(M). For higher x values the samples become superconducting and the MS spectra below and above T(C) are almost identical, indicating that the MS technique are not sensitive enough to the superconducting transition.