Nanocrystalline (Fe1-xNix)(81)Nb7B12 (x = 0, 0.25, 0.5, 0.75) and Vitroperm alloys were studied by Mossbauer spectroscopy after neutron irradiation at fluences of 1016 n/cm(2) and 10(17) n/cm(2). From structure analyses, we have identified ferromagnetic bcc-FeNi in nanocrystalline state and partly paramagnetic (Fe-Ni)(23)B-6 phase. Neutron irradiation had an influence on the magnetic microstructure, which is manifested in the change of the Mossbauer parameters, such as the direction of net magnetic moment, the intensity of internal magnetic field and the volumetric fraction. The results indicate that the changes of the microscopic magnetic parameters, induced by neutron irradiation, depend on iron and nickel content. Significant radiation damage started at neutron fluence of 10(17) n/cm(2).
