Radiation effects in amorphous FexNi80−xP14B6

Change in the Curie temperature and magnetic saturation of the amorphous ferromagnetic series FexNi80−xP14B6 for 20?x?34 induced by proton bombardment have been studied, and correlated with small angle x-ray scattering measurements performed for x = 20 at Oak Ridge National Laboratory. Both the Curie temperature and the low temperature saturation magnetization increase with proton fluence up to 1016 cm−2 but are constant for higher fluences. Protons of energy 2.25 MeV (range much greater than the sample thickness) are more effective at producing changes than protons of energy 0.25 MeV (range much less than sample thicness). Thus, hydrogen implantation is eliminated as the principal source of the observed changes. In addition, careful attention to sample temperature during irradiation excludes thermal annealing as the origin of the effect. Proton bombardment at the same fluences produces scattering centers that are observed by small angle x-ray scattering. The concentration of scattering centers increases with proton fluence up to 1016 cm−2, but remains constant thereafter. The size of the centers remains constant at about 16–30 Å. Possible structural changes to account for these observations are incipient recrystallization, void formation, and phosphorous segregation.

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