Effect of high-energy ion irradiation on magnetic properties in Fe-Pt invar alloys

Ono, Fumihisa*; Kanamitsu, Hiroaki*; Matsushima, Yasushi*; Chimi, Yasuhiro; Ishikawa, Norito   ; Kambara, Tadashi*; Iwase, Akihiro*

Specimens of both ordered and disordered Fe-28.3at.%Pt alloys were irradiated with 200-MeV Xe ions to the fluence of 10 ions/cm. Measurements of AC-susceptibility-temperature curves were made for each specimen before and after the irradiation by using a specially designed apparatus for rapid measurements. In contrast to the expectation from the previous results for Fe-Ni alloys, in disordered Fe-Pt invar alloy the Curie temperature, T decreased about 15 K by the irradiation. This fact cannot be explained by considering the lattice expansion effect alone. In Fe-Pt invar alloys the effect of lattice expansion may be cancelled out by some other effects which may be originated from the large difference in atomic mass between the two elements. For ordered Fe-Pt alloy, T decreased as large as 60 K with the same fluence. The value of T for both ordered and disordered Fe-Pt invar alloys coincide with each other after the irradiation. This fact can be explained by considering that the ordered state becomes disordered by the irradiation.