Modification of Fe–Pd invar alloys by high-energy heavy ions

Measurements of AC-susceptibility versus temperature curves were made in thin plates of disordered Fe-30.6 at.%Pd and Fe-34 at.%Pd invar alloys before and after high-energy heavy ion irradiation. In both alloys the Curie temperature increased about 20–25 K by the irradiation of 200 MeV Xe-ions to the fluence of 1014 ions/cm2. By comparing these data with the previous one for Fe–Ni and Fe–Pt invar alloys, it was concluded that there exist at least two mechanisms having opposite contribution. One is the negative pressure effect through the lattice expansion and another is the selective knock on of constituent atoms through the difference of the atomic radius.