Influence of the rare-earth site nonstoichiometry and Mn doping on the electronic structure of TbNi2

•Spectral and magnetic properties of Tb1−δNi2Mnx are investigated by the CPA method.•The CPA calculations are based on the LDA+U+SO scheme.•Vacancy and Mn impurity in Tb site and Mn impurity in Ni site are considered together.•Impurities in Tb site lead to decrease of f-electrons spin and orbital moments values.•The Mn impurity in Ni site causes the reduction of Ni d-shell electron number.

Electronic structure and magnetic properties of Tb1−δNi2Mnx alloys (δ=0, 0.04 and 0≤x≤1) are investigated within the Coherent Potential Approximation (CPA) taking into account the strong electronic correlations (U) in Tb f-shell and the spin–orbit coupling (SO) in f-Tb, d-Ni, and d-Mn shells. Explicit consideration of electronic correlations and spin–orbit coupling is necessary for correct description of f-levels positions in the spectrum. Both vacancy in Tb site and manganese impurity in Tb and Ni sites cause the decrease of the total magnetic moment value J keeping its direction [111]. The absolute value of |J| decreases linearly with the increase of Mn impurity concentration; the ratio of |J|(Tb0.96Ni2Mn1)/|J|(Tb0.96Ni2) is 0.66 which agrees well with experiment.