Modification of magnetic properties in Fe-Ni alloy thin films induced by energetic ion irradiation

Chimi, Yasuhiro; Ishikawa, Norito   ; Iwase, Akihiro*; Ono, Fumihisa*

We have already found that high-energy heavy ion irradiation modifies magnetic properties in Fe-Ni invar alloys, i.e. that the Curie temperature, , increases by the irradiation. In the present paper, in order to clarify the mechanism of the modification, we investigate a dominant irradiation parameter for the modification. Specimens of Fe-Ni and Fe-Ni-Mn alloy thin films (500 nm in thickness) are prepared on MgO(100) single crystal substrates by rf magnetron sputtering. The specimens are irradiated at room temperature with several kinds of ions in the energy and mass ranges of 1.0-200 MeV and H-Au. A large increase in is observed for comparatively low-energy ion irradiation. This result suggests that the dominant process for the modification is the elastic interaction between incident ions and target atoms. The dependence on ion energy and fluence of the increase in gives information on a dominant irradiation parameter.