Enhancement of Curie Temperature (T ^sub c^) and Magnetization of Fe-Ni Invar alloy Through Cu Substitution and with He^sup +2^ Ion Irradiation

Issue Title: Special Section: 2015 Electronic Materials Conference. Guest Editors: Joshua Caldwell, Joshua Zide, Suzanne Mohney, Jamie Phillips, F. Shadi Shahedipour-Sandvik, Nadeem Mahadik, Fareed Qhalid, Suchi Guha, Rachel Goldman, Jian Xu, Angel Yanguas-Gil, Ganesh Balakrishnan The magnetic properties of ternary Fe-Ni-Cu invar alloys are affected by ion irradiation, which goes on increasing with increasing ion fluence (Φ), and by increasing Cu content. In the present study, the ions used are He^sup +2^ with 2 MeV energy and with 1 × 10^sup 13^ cm^sup -2^, 1 × 10^sup 14^ cm^sup -2^, 5 × 10^sup 14^ cm^sup -2^, 1 × 10^sup 15^ cm^sup -2^ and 5 × 10^sup 15^ cm^sup -2^ fluence (dose) for irradiation purpose. The face centered cubic structure of the alloy was investigated after ion irradiation using x-ray diffraction (XRD) and found unchanged. However, the peaks become broader with increasing ion dose. Additionally, the lattice fluctuations were observed in XRD study. Curie temperature (T ^sub c^) is also increased after irradiation. Many factors are considered here for the reason for increasing T ^sub c^, such as the stopping of incident ions, atomic mixing effect at micro scale level owing to ion irradiation, which might change local concentration and ordering already reported in diffuse scattering, and as a result the Fe-Fe interatomic distance and the Fe-Fe coupling are changed. A comparative study shows that the effect of irradiation on T ^sub c^ and magnetization with increasing ion fluence is more distinctive than the addition of Cu.