  We report 57Fe Mossbauer spectral results in pure and doped Ba(Fe1-xNix)2As2
with x=0.01 and 0.03. We show that all these materials present a first-order
magnetic transition towards a magnetically ordered state. In the doped
compounds, a broad distribution of Fe hyperfine fields is present in the
magnetic phase. We successfully fit the Mossbauer data in Ba(Fe1-xNix)2As2 in
the framework of two different models: 1) an incommensurate spin density wave;
2) a dopant-induced perturbation of the Fe polarization, recently proposed to
interpret 75As NMR data in Ba(Fe1-xNix)2As2, which is valid only in the very
dilute limit x=0.01. Moreover, we show here that these NMR data can also be
successfully analysed in terms of the 'incommensurate model' for all doping
contents by using the parameters obtained from the Mossbauer spectral analysis.
Therefore it is not possible to rule out the presence of an incommensurate spin
density wave on the basis of the 75As NMR data.
