Effect of GeV-Ion irradiation on magnetic properties of Fe-Ni invar alloys

High-energy ion irradiation was performed using a ring-cyclotron installed at the Institute of Physical and Chemical Research (RIKEN). The incident ions were Ta with the energy of 3.71 GeV, and the fluence was fixed to 5 × 1012 ions/cm2. As a target, three sheets of square plates of Fe-30.2 at.% Ni invar alloys were put one upon another. The shift of the Curie temperature TC of the first sample was 14 K, while that of the second one was 22 K. Comparing these two, the shift was as large as 46 K in the last sample in which ions stopped in the middle. It was concluded that there are at least two different mechanisms that contribute to the shift of TC.